java assignment default

Java default Initialization of Instance Variables and Initialization Blocks

1. default initialization of instance variables in java.

• Integer numbers have default value: 0
• for int type: 0
• for byte type: (byte) 0
• for short type: (short) 0
• for long type: 0L
• Floating point numbers have default value: 0.0
• for float type: 0.0f
• for double type: 0.0d
• Boolean variables have default value: false
• Character variables have default value: ‘\u0000’
• Object references have default value: null

2. Default Initialization of Arrays in Java

3. instance initialization blocks in java, 4. static initialization blocks in java, other recommended tutorials:.

• 9 Rules about Constructors in Java
• 12 Rules and Examples About Inheritance in Java
• 12 Rules of Overriding in Java You Should Know
• 10 Java Core Best Practices Every Java Programmer Should Know
• Understand Interfaces in Java
• Understand how variables are passed in Java
• Understand access modifiers in Java
• Understand encapsulation in Java

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Does Java have default parameters?

Short answer: No. Fortunately, you can simulate them. Many programming languages like C++ or modern JavaScript have a simple option to call a function without providing values for its arguments. In Java, default method parameters require a bit more typing to achieve this effect in comparison to other languages. From this article, you will learn how the default method parameters work in Java .

1. Java default parameters in practice

The syntax of Java language doesn’t allow you to declare a method with a predefined value for a parameter. Fortunately, you can achieve the same effect with simple code constructions.

There are several options that you may use to simulate behavior known from other programming languages. You can:

• use method overloading
• allow nulls as an input
• declare a method with Java Varargs

Let’s take a closer look at these options.

1.1. Java default parameters with method overloading

Probably the best option to achieve default method parameters in Java is by using the method overloading. Method overloading allows you to declare several methods with the same name but with a different number of parameters.

How to use method overloading to simulate default method parameters?

By calling a more complex method by a simpler one.

Here is a practical example of a method which allows you to query for an optional number of some documents:

The only required parameter is a query string. As you can see, you only have to implement the method with the highest number of parameters. To clarify, t he simple method is just a proxy that passes its parameter to the more complex method and provides default parameter values for the optional arguments.

In comparison to other options, the main advantage of method overloading is the simplicity for the client code. You can easily read what set of parameters is allowed for a given method.

Although method overloading is strongly recommended, it’s worth knowing about other possibilities.

1.2. Allowing Nulls as method parameters

Another option is to declare a single method that accepts all possible parameters. Next, in the body of the method, you can check which parameters are nulls and assign them default values.

In this approach, our previous example looks as follows:

There are two main disadvantages to this approach. First, you still need to pass all arguments in client code. Even if some of them are nulls. Second, you need to know which parameters are nullable as you can’t tell that just by looking at the method declaration.

What is more, many developers consider reassinging method parameters as bad practice as it makes the code harder to follow. With this in mind, many static code analysis tools allow you to check for this kind of code smell.

Some people suggest wrapping parameters which aren’t required inside Java 8 Optional class. However, the Optional type was designed for method outputs and not inputs. If you are interested why, check out my other article about Java Optional use cases .

1.3. Varargs parameter

The Varargs option is limited only to arguments of the same type and meaning. Therefore, it doesn’t actually solve the problem of default parameters in Java methods. But you may consider it in some cases.

Technically, it’s even possible to use Varargs as a single optional parameter. In this case, you don’t have to pass null in the client code to use the default value. Yet, it rather feels like an awful hack. I recommend sticking to method overloading.

2. Java default parameters in long parameter list

The main problem with method overloading as a solution for default parameter values reveals itself when a method accepts multiple parameters. Creating an overloaded method for each possible combination of parameters might be cumbersome.

To deal with this issue, you should introduce the Parameter Object pattern .

What is it?

Simply put, the Parameter Object is a wrapper object for all parameters of a method.

But wait! Aren’t we just moving the problem of the long parameter list from a method to the constructor of the new class?

Indead, we are. But class constructors give us one additional solution for the problem which is the Builder pattern.

2.1. Solving Java default parameters with Parameter Object

As mentioned before, the first thing you need is a parameter object class that wraps the list of method parameters. Let’s see how it can look like for a method from the previous example:

As you can see, the implemented parameter object is nothing more than just a regular POJO. The advantage of the Parameter Object over a regular method parameter list is the fact that class fields can have default values . Just like in the above example.

That’s it. Now you have all default parameters in a single place.

2.2. … and  Builder patterns

Once you create a wrapper class for the method parameter list you should also create a corresponding builder class. Usually, you’ll do it as an inner static class. 

But don’t type builders alone, automate this work! 

Popular Java IDEs provide plugins that generate builder classes.

In our example the builder will look as follows:

The final step is to use the builder to construct a new parameter object. In this case, you assign only selected parameters. For those parameters you skip, their default values are going to be used. Here’s an example:

Our example is really simple as the method has only three parameters so it might look like overengineering. In fact, the solution for default parameters using Parameter Object and Builder shines when the list of method parameters is much longer.

Let’s sum up. 

Java doesn’t have a simple solution for default method parameters as available in other common programming languages. Yet, you can simulate it using other Java constructions and patterns. In addition, you learn a simple approach with method overloading which works for methods with a short parameter list. For complex methods, the Parameter Object pattern is more flexible.

If you find the article useful, please share it with your friends. Don’t forget to subscribe so I can notify you about other similar posts.

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• Java Default Parameters
• Java Howtos

Default Parameters in Java

Set default parameters using var-args in java, set default parameters as empty string in java, set default parameters using var-args with any number of arguments in java.

This tutorial introduces how to implement default parameters in Java.

A default parameter is used when no value is passed. It is helpful when we want to pass limited arguments while the method accepts multiple arguments. For example, a method accepts three arguments, but if we wish to pass only two arguments during the method call, then the Java compiler uses the default value of the third argument to avoid any compilation error.

Java does not support default parameters value, but we can achieve it using some built-in solutions such as var-args or method overloading. Let’s see some examples.

In this example, we use the method overloading approach to set the default parameter value. However, this is not a fine solution but can be used as an alternative. Notice, we pass 0 as the default value while calling the add() method.

This approach doesn’t work if we have two optional parameters of the same type, and any of them can be omitted.

This is another approach where we use the variable args feature to set default parameters. The var-args allows passing a variable length of arguments of the same type. See the example below.

In the case of string parameters, we can set an empty string to the parameters; however, this string holds null as the default value. See the example below.

In the case of var-args, we are free to provide any number of arguments while calling the method. So, if you want to provide only limited arguments, then it will work fine. See the example below.

Related Article - Java Method

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Default Constructor in Java – Class Constructor Example

In this article, we will talk about constructors, how to create our own constructors, and what default constructors are in Java.

What is a constructor?

As a class-based object-oriented programming term, a constructor is a unique method used to initialize a newly created object (class). There are a few rules you must follow when creating constructors. These rules include:

• The name of the constructor must be the same as the class name.
• The constructor must have no return type.

Before we proceed, let's see what a class looks like in Java:

The code above shows a class called Student with three attributes – firstName , lastName , and age . We will assume that the class is supposed to be a sample for registering students. Recall that the three attributes do not have any values so none of the information is hard coded.

Now we will use constructors to create a new instance of our Student object. That is:

We have created a constructor which we used to initialize the attributes defined in the Student object. The code above is an example of a no-argument constructor. Let's see an example of a different kind now:

Now we have created a parameterized constructor . A parameterized constructor is a constructor created with arguments/parameters. Let's break it down.

We created a new constructor that takes in three arguments – two strings and an integer.

We then linked these arguments to the attributes we defined when we created our class.  Now we have initialized the Student object using a constructor.

Lastly, we created a new instance of the Student object and passed in our arguments. We were able to pass in these arguments because we had already defined them in a constructor.

I created one constructor with three arguments, but you can also create separate constructors for initializing each attribute.

Now that you know what a constructor is in Java and how to use it, let's now look into default constructors.

What is a default constructor?

A default constructor is a constructor created by the compiler if we do not define any constructor(s) for a class. Here is an example:

Can you spot the difference between this and the two previous examples? Notice that we did not define any constructor before creating   myStudent to initialize the attributes created in the class.

This will not throw an error our way. Rather, the compiler will create an empty constructor but you will not see this constructor anywhere in the code – this happens under the hood.

This is what the code above will look like when the compiler starts doing its job:

A lot of people mix up the default constructor for the no-argument constructor, but they are not the same in Java. Any constructor created by the programmer is not considered a default constructor in Java.

In this article, we learned what constructors are and how we can create and use them to initialize our objects.

We also talked about default constructors and what makes them different from no-argument constructors.

Happy Coding!

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If you come across any mistakes or bugs, please email me to [email protected] .

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java default if null

Answered on: Wednesday 27 December, 2023 / Duration: 10 min read

Programming Language: Java , Popularity : 3/10

Solution 1:

In Java, handling null values is a common scenario to avoid NullPointerException . The Optional class introduced in Java 8 provides a way to deal with null values in a more functional manner. However, before Java 8, developers used different methods like ternary operators or if-else conditions to handle null values.

Let's look at some methods to provide a default value if a variable is null .

### 1. Using if-else:

### 2. Using ternary operator:

This is just a more concise way of achieving the same as the if-else method.

### 3. Using Optional (Java 8 and later):

With the introduction of the Optional class, you can handle nulls in a more functional way:

In the above examples, the variable name is checked for null . If it is null , a default value ( DefaultName in this case) is assigned. This way, you ensure that the code does not throw a NullPointerException when trying to operate on a null value.

Solution 2:

Java default if null

The default keyword in Java can be used to provide a default value for a method or variable that may be null. This can be useful for ensuring that a method or variable always has a value, even if it is not explicitly set.

To use the default keyword, simply specify the default value after the type of the method or variable, enclosed in curly braces. For example:

In this example, the getName() method returns the value of the name variable. If name is null, the method returns the default value of "John Doe".

The default keyword can also be used with variables. For example:

In this example, the name variable is initialized to null. However, the getName() method is called to set the default value of the variable.

The default keyword can be a useful way to ensure that methods and variables always have a value, even if they are not explicitly set. This can help to prevent errors and ensure that your code is always running as expected.

Code examples

The following code examples demonstrate how to use the default keyword in Java.

Example 1: Using the default keyword with a method

Example 2: Using the default keyword with a variable

The following are the outputs of the code examples above.

Solution 3:

[1]: https://stackoverflow.com/questions/31412294/java-check-not-null-empty-else-assign-default-value "" [2]: https://stackoverflow.com/questions/44052059/java-string-set-default-value-if-null "" [3]: https://www.educative.io/answers/what-is-objectutilsdefaultifnull-in-java "" [4]: https://stackoverflow.com/questions/46414342/get-default-value-if-the-object-is-null-in-java "" [5]: https://stackoverflow.com/questions/7317494/value-null-by-default-in-string ""

This is Bing. I can help you with your question about Java default values for null objects.

In Java, there are different ways to assign a default value to an object if it is null. One way is to use the ternary operator, which is a shorthand for an if-else statement. For example:

Another way is to use the Optional class, which is a wrapper for an object that may or may not be present. The Optional class provides methods to check if the object is present, and to get the object or a default value otherwise. For example:

A third way is to use the ObjectUtils class from Apache Commons Lang, which provides utility methods for working with objects. One of these methods is defaultIfNull, which returns the first argument if it is not null, or the second argument otherwise. For example:

These are some of the common ways to assign a default value to an object if it is null in Java. You can find more information and examples in the following sources:

- [Java - Check Not Null/Empty else assign default value](https://stackoverflow.com/questions/31412294/java-check-not-null-empty-else-assign-default-value) - [Java string set default value if null](https://stackoverflow.com/questions/44052059/java-string-set-default-value-if-null) - [What is ObjectUtils.defaultIfNull in Java?](https://www.educative.io/answers/what-is-objectutilsdefaultifnull-in-java) - [Get default value if the object is null in Java](https://stackoverflow.com/questions/46414342/get-default-value-if-the-object-is-null-in-java) - [Value "null" by default in String](https://stackoverflow.com/questions/7317494/value-null-by-default-in-string)

I hope this helps you with your Java programming. Have a nice day!

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Java 22 and IntelliJ IDEA

Java 22 is here, fully supported by IntelliJ IDEA 2024.1 , allowing you to use these features now!

Java 22 has something for all – from new developers to Java experts, features related to performance and security for big organizations to those who like working with bleeding edge technology, from additions to the Java language to improvements in the JVM platform, and more.

It is also great to see how all these Java features, release after release, work together to create more possibilities and have a bigger impact on how developers create their applications that address existing pain points, perform better and are more secure.

This blog post doesn’t include a comprehensive coverage of all the Java 22 features. If you are interested in that, I’d recommend you to check out this link to know everything about what’s new and changing in Java 22, including the bugs.

In this blog post, I’ll cover how IntelliJ IDEA helps you get started, up and running with some of the Java 22 features, such as, String Templates , Implicitly Declared Classes and Instance Main Methods , Statements before super() , and Unnamed variables and patterns .

Over the past month, I published separate blog posts to cover each of these topics in detail. If you are new to these topics, I’d highly recommend you check out those detailed blog posts (I’ve included their links in the relevant subsections in this blog post). In this blog post, I’ll cover some sections from those blog posts, especially how IntelliJ IDEA supports them. Let’s start by configuring IntelliJ IDEA to work with the Java 22 features.

IntelliJ IDEA Configuration

Java 22 support is available in IntelliJ IDEA 2024.1 Beta . The final version will release soon in March 2024.

In your Project Settings, set the SDK to Java 22. For the language level, select ‘22 (Preview) – Statements before super(), string templates (2nd preview etc.)’ on both the Project and Modules tab, as shown in the below settings screenshot:

If you do not have Java 22 downloaded to your system yet, don’t worry; IntelliJ IDEA has your back! You could use the same Project settings window, select ‘Download JDK’, after you click on the drop down next to SDK. You’ll see the below popup that would enable you to choose from a list of vendors (such as Oracle OpenJDK, GraalVM, Azul Zulu and others):

With the configuration under our belt, let’s get started with covering one of my favorite new features, that is, String Templates.

String Templates (Preview Language feature) The existing String concatenation options are difficult to work with and could be error prone; String templates offer a better alternative, that is, String interpolation with additional benefits such as validation, security and transformations via template processors.

Please check out my detailed blog post on this topic: String Templates in Java – why should you care? if you are new to this topic. It covers all the basics, including why you need String Templates, with multiple hands-on examples on built-in and user defined String processors.

IntelliJ IDEA can highlight code that could be replaced with String Templates Let’s assume you defined the following code to log a message that combines string literals and variable values using the concatenation operator:

The output from the preceding code could be an issue if you miss adding spaces in the String literals. The code isn’t quite easy to read or understand due to multiple opening and closing double quotes, that is, " and the + operator, and it would get worse if you add more literals, or variable values to it.

You could replace the preceding code with either StringBuilder.append() , String.format() or String.formatted() method or by using the class MessageFormat (as shown in my detailed blog post on this topic), but each of these methods have their own issues.

Don’t worry; IntelliJ IDEA could detect such code, suggest that you could replace it with String template, and do that for you, as shown below. It doesn’t matter if you are not even aware of the syntax of the String templates, IntelliJ IDEA has your back 🙂

Embedded expressions in String Templates and IntelliJ IDEA The syntax to embed a remplate expression (variable, expressible or a method call) is still new to what Java developers are used to and could be challenging to use without help. Don’t worry, IntelliJ IDEA has your back!

Each embedded expression must be enclosed within \{}. When you type \{, IntelliJ IDEA adds the closing ‘}’ for you. It also offers code completion to help you select a variable in scope, or any methods on it. If the code that you insert doesn’t compile, IntelliJ IDEA will highlight that too (as a compilation error), as shown in the following gif:

Using String Templates with Text Blocks Text blocks are quite helpful when working with string values that span multiple lines, such as, JSON, XML, HTML, SQL or other values that are usually processed by external environments. It is common for us Java developers to create such string values using a combination of string literals and variable values (variables, expressions or method calls).

The example below shows how IntelliJ IDEA could detect and create a text block using String templates for multiline string values that concatenates string literals with variable values. It also shows how IntelliJ IDEA provides code completion for variable names within such blocks. When you type in \{ , IntelliJ IDEA adds } . As you start typing the variable name countryName , it shows the available variables in that context:

Language injection and String Templates You could also inject a language or a reference in string values that spans single line or multiple lines, such as, a text block. By doing so, you get comprehensive coding assistance to edit the literal value. You could avail of this feature temporarily or permanently by using the @Language annotation, as shown below:

You can check out this link for detailed information on the benefits and usage of injecting language or reference in IntelliJ IDEA.

Predefined Template Processors With the String templates, you get access to predefined processors like the STR , FMT and RAW . I’d highly recommend you to check out my detailed blog post on String templates for multiple hands-on examples on it.

Custom Template Processor

Let’s work with a custom String template that isn’t covered in my previous blog post.

Imagine you’d like to create an instance of a record, say, WeatherData , that stores the details of the JSON we used in the previous section. Assume you define the following records to store this weather data represented by the JSON in the previous section:

You could create a method to return a custom String template that would process interpolated string, accept a class name ( WeatherData for this example) and return its instance:

Depending on the logic of your application, you might want to escape, delete or throw errors for the special characters that you encounter in the the JSON values interpolated via template expressions, as follows (the following method chooses to escape the special characters and include them as part of the JSON value):

You could initialize and use this custom JSON template processor as below. Note how elegant and concise the solution is with a combination of textblocks and String templates. The JSON is easy to read, write and understand (thanks to text blocks). The template expressions make it clear and obvious about the sections that are not constants and would be injected by the variables. At the end, the custom template processor WEATHER_JSON would ensure the resultant JSON is validated according to the logic you defined and returns an instance of WeatherData (doesn’t it sound magical?) :

Do not miss to check out my detailed blog post on this topic: String Templates in Java – why should you care? to discover how you could use the predefined String templates like FMT , to generate properly formatted receipts for, say, your neighborhood stationery store, or, say encode and decode combinations like :) or :( to emojis like 🙂 or ☹️. Does that sound fun to you?

Implicitly Declared Classes and Instance Main Methods (Preview language feature)

Introduced as a preview language feature in Java 21, this feature is in its second preview in Java 22.

It would revolutionize how new Java developers would get started learning Java. It simplifies the initial steps for students when they start learning basics, such as variable assignment, sequence, conditions and iteration. Students no longer need to declare an explicit class to develop their code, or write their main() method using this signature – public static void main(String []) . With this feature, classes could be declared implicitly and the main() method can be created with a shorter list of keywords.

If you are new to this feature, I’d highly recommend you to check out my detailed blog post: ‘HelloWorld’ and ‘main()’ meet minimalistic on this feature. In this blog post, I’ll include a few of the sections from it.

Class ‘HelloWorld’ before and after Java 21

Before Java 21, you would need to define a class, say, HelloWorld , that defined a main() method with a specific list of keywords, to print any text, say, ‘Hello World’ to the console, as follows:

With Java 21, this initial step has been shortened. You can define a source code file, say, HelloWorld.java, with the following code, to print a message to the console (it doesn’t need to define a class; it has a shorter signature for method main() ):

The preceding code is simpler than what was required earlier. Let’s see how this change could help you focus on what you need, rather than what you don’t.

Compiling and executing your code

Once you are done writing your code, the next step is to execute it.

On the command prompt, you could use the javac and java commands to compile and execute your code. Assuming you have defined your code in a source code file HelloWorld.java, you could use the following commands to run and execute it:

Since Java 11, it is possible to skip the compilation process for code defined in a single source code file, so you could use just the second command (by specifying the name of the source code file, as follows):

However, since instance main methods and implicit classes is a preview language feature, you should add the flag --enable-preview with --source 22 with these commands, as follows:

Sooner or later, you might switch to using an IDE to write your code. If you wish to use IntelliJ IDEA for creating instance main methods, here’s a quick list of steps to follow. Create a new Java project, select the build system as IntelliJ (so you could use Java compiler and runtime tools), create a new file, say, HelloWorld.java with your instance main method and set the properties to use Java 22, before you run your code, as shown in the following gif (It could save you from typing out the compilation/ execution commands on the command prompt each time you want to execute your code):

Are you wondering if it would be better to create a ‘Java class’ instead of a ‘File’ in the ‘src’ folder? The option of selecting a Java class would generate the body of a bare minimum class, say, public class HelloWorld { } . Since we are trying to avoid unnecessary keywords in the beginning, I recommended creating a new ‘File’ which wouldn’t include any code.

What else can main() do apart from printing messages to the console?

As included in my detailed post on this topic , I included multiple hand-on examples to show what you could achieve via just the main() method:

• Example 1. Variable declarations, assignments and simple calculations
• Example 2. Print patterns, such as, big letters using a specified character
• Example 3. Animating multiline text – one word at a time
• Example 4. Data structure problems
• Example 5. Text based Hangman game

The idea to include multiple examples as listed above is to demonstrate the power of sequence, condition and iteration all of which can be included in the main() method, to build good programming foundations with problem solving skills. By using the run command or the icon to run and execute their code in IntelliJ IDEA, new programmers reduce another step when getting started.

Changing an implicit class to a regular class

When you are ready to level up and work with other concepts like user defined classes, you could also covert the implicit classes and code that we used in the previous examples, to regular classes, as shown below:

What happens when you create a source code file with method main(), but no class declaration?

Behind the scenes, the Java compiler creates an implicit top level class, with a no-argument constructor, so that these classes don’t need to be treated in a way that is different to the regular classes.

Here’s a gif that shows a decompiled class for you for the source code file AnimateText.java:

Variations of the main method in the implicit class

As we are aware, a method can be overloaded. Does that imply an implicit class can define multiple main methods? If yes, which one of them qualifies as the ‘main’ method? This is an interesting question. First of all, know that you can’t define a static and non-static main method with the same signature, that is, with the same method parameters. The following method are considered valid main() methods in an implicit class:

If there is no valid main method detected, IntelliJ IDEA could add one for you, as shown in the following gif:

Educators could use this feature to introduce other concepts to the students in an incremental way

If you are an educator, you could introduce your students to other commonly used programming practices, such as creating methods- that is delegating part of your code to another method and calling it from the main method. You could also talk about passing values vs. variables to these methods.

The following gif shows how to do it:

Statements before super() – a preview language feature

Typically, we create alternative solutions for tasks that are necessary, but not officially permitted. For instance, executing statements before super() in a derived class constructor was not officially allowed, even though it was important for, say, validating values being passed to the base class constructor. A popular workaround involved creating static methods to validate values and then calling these methods on the arguments of super() . Though this approach worked well, it could make the code look complicated. This is changing with Statements before super() , a preview language feature in Java 22.

By using this feature, you can opt for a more direct approach, that is, drop the workaround of creating static methods, and execute code that validates arguments, just before calling super() . Terms and conditions still apply, such as, not accessing instance members of a derived class before execution of super() completes.

An example – Validating values passed to super() in a derived class constructor Imagine you need to create a class, say, IndustryElement , that extends class Element , which is defined as follows:

The constructor of the class Element misses checking if the atomicNumber is in the range of 1-118 (all known elements have atomic numbers between 1 to 118). Often the source code of a base class is not accessible or open for modification. How would you validate the values passed to atomicNumber in the constructor of class IndustryElement ?

Until Java 21, no statements were allowed to execute before super() . Here’s one of the ways we developers found a workaround by defining and calling static methods (static methods belong to a class and not to instances and can be executed before any instance of a class exists):

Starting Java 22, you could inline the contents of your static method in the constructor for your derived class, as shown in the following gif:

Here’s the resultant code for your reference:

Where else would you use this feature? If you are new to this feature, I’d recommend that you check out my detailed blog post, Constructor Makeover in Java 22 , in which I’ve covered this feature in detail using the following examples:

• Example 2 – base class constructor parameters that use annotations for validations
• Example 3 – Transforming variable values received in a derived class constructor, before calling a base class constructor.
• Example 4 – Executing statements before this() in constructor of Records
• Example 5 – Executing statements before this() in Enum constructors
• Example 6 – Executing statements before this() in classes

How does it work behind the scenes? The language syntax has been relaxed but it doesn’t change or impact the internal JVM instructions. There are no changes to the JVM instructions for this new feature because the order of execution of the constructors still remains unchanged – from base class to a derived class. Also, this feature still doesn’t allow you to use members of a derived class instance, until super() executes.

Let’s access and compare the instruction set of the constructor of class IndustryElement , before and after its modification – one that can execute statements before super() and the one that doesn’t. To do so, use the following command:

Here’s the instruction set for the constructor that doesn’t explicitly execute statements before super() and calls static methods to validate range of atomic number:

Here’s instruction set for the constructor that explicitly executes statements before super() to validate range of atomic number:

The most important point to note here is that in both the cases, the constructor of the base class, that is, Element is called, after the execution of all other statements. Essentially, it means, you are still doing the same thing, it is just packaged in a way that makes things easier for you.

I understand it is difficult to remember what each of these instruction codes means. Access the following link and search for the instruction code and following the above instructions set would be a breeze:

https://docs.oracle.com/javase/specs/jvms/se21/html/jvms-6.html#jvms-6.5.aload_n

Can you execute ‘any’ statements before calling super()?

No. If the statements before super() try to access instance variables or execute methods of your derived class, your code won’t compile. For example, if you change the static checkRange() method to an instance method, your code won’t compile, as shown below:

Unnamed Variables and Patterns

Starting Java 22, using Unnamed Variables & Patterns you can mark unused local variables, patterns and pattern variables to be ignored, by replacing their names (or their types and names) with an underscore, that is, _ . Since such variables and patterns no longer have a name, they are referred to as Unnamed variables and patterns. Ignoring unused variables would reduce the time and energy anyone would need to understand a code snippet. In the future, this could prevent errors :-). This language feature doesn’t apply to instance or class variables.

Are you wondering if replacing unused variables with _ is always a good idea, or do they imply code smells and should you consider refactoring your codebase to remove them? Those are good questions to ask. If you are new to this topic, I’d recommend you to check out my detailed blog post: Drop the Baggage: Use ‘_’ for Unnamed Local Variables and Patterns in Java 22 to find out answer to this question.

Since this is not a preview language feature, set Language Level in your Project Settings to ‘22 – Unnamed variables and patterns’ on both the Project and Modules tab, as shown in the below settings screenshot:

A quick example

The following gif gives a sneak peek into how an unused local variable, connection, is detected by IntelliJ IDEA, and could be replaced with an underscore, that is, _ .

The modified code shown in the preceding gif makes it clear that the local variable defined in the try-with-resources statement is unused, making it concise and easier to understand.

Unused Patterns and Pattern variables in switch constructs

Imagine you defined a sealed interface, say, GeometricShape , and records to represent shapes, such as, Point , Line , Triangle , Square , as shown in the following code:

Now assume you need a method that accepts an instance of GeometricShape and returns its area. Since Point and a Line are considered one-dimensional shapes, they wouldn’t have an area. Following is one of the ways to define such method that calculates and returns area:

In the previous example, the patterns int x , int y , Point a and Point B (for case label Line) remain unused as detected by IntelliJ IDEA. These could be replaced by an _ . Also, since all the record components of the case Point remain unused, it could be replaced as Point _ . This could also allow us to merge the first and second case labels. All of these steps are shown in the following gif:

Here’s the modified code for your reference:

In the preceding example, you can’t delete the pattern variables even if they are unused. The code must include the cases when the instance passed to the method calcArea() is of type Point and Line , so that it could return 0 for them.

Unused Patterns or variables with nested records

This feature also comes in quite handy for nested records with multiple unused patterns or pattern variables, as demonstrated using the following example code:

In the preceding code, since the if condition in the method checkFirstNameAndCountryCodeAgain uses only two pattern variables, others could be replaced using _ ; it reduced the noise in the code too.

Where else can you use this feature? Checkout my detailed detailed blog post: Drop the Baggage: Use ‘_’ for Unnamed Local Variables and Patterns in Java 22 to learn more about other use cases where this feature can be used:

• Requirements change, but you need side effects of constructs like an enhanced for-loop
• Unused parameters in exception handlers; whose signature can’t be modified
• Unused auto-closeable resources in try-with-resources statements

It isn’t advisable to use this feature without realising if an unused variable or pattern is a code smell or not. I used these examples to show that at times it might be better to refactor your code to get rid of the unused variable instead of just replacing it with an underscore, that is, _ .

• Unused lambda parameter
• Methods with multiple responsibilities

Preview Features

‘String Templates’, ‘Implicitly Declared Classes and Instance Main Methods’ and ‘Statements before super()’ are preview language features in Java 22. With Java’s new release cadence of six months, new language features are released as preview features. They may be reintroduced in later Java versions in the second or more preview, with or without changes. Once they are stable enough, they may be added to Java as a standard language feature.

Preview language features are complete but not permanent, which essentially means that these features are ready to be used by developers, although their finer details could change in future Java releases depending on developer feedback. Unlike an API, language features can’t be deprecated in the future. So, if you have feedback about any of the preview language features, feel free to share it on the JDK mailing list (free registration required).

Because of how these features work, IntelliJ IDEA is committed to only supporting preview features for the current JDK. Preview language features can change across Java versions, until they are dropped or added as a standard language feature. Code that uses a preview language feature from an older release of the Java SE Platform might not compile or run on a newer release.

In this blog post, I covered four Java 22 features – String Templates , Implicitly Declared Classes and Instance Main Methods , Statements before super() , and Unnamed variable and patterns .

String Templates is a great addition to Java. Apart from helping developers to work with strings that combine string constants and variables, they provide a layer of security. Custom String templates can be created with ease to accomplish multiple tasks, such as, to decipher letter combinations, either ignoring them or replacing them for added security.

Java language designers are reducing the ceremony that is required to write the first HelloWorld code for Java students, by introducing implicitly declared classes and instance main methods. New students can start with bare minimum main() method, such as, void main() and build strong programming foundation by polishing their skills with basics like sequence, selection and iteration.

In Java 22, the feature Statements before super() lets you execute code before calling super() in your derived class constructors, this() in your records or enums, so that you could validate the method parameters, or transform values, as required. This avoids creating workarounds like creating static methods and makes your code easier to read and understand. This feature doesn’t change how constructors would operate now vs. how they operated earlier – the JVM instructions remain the same.

Unnamed variables are local to a code construct, they don’t have a name, and they are represented by using an underscore, that is, _ . They can’t be passed to methods, or used in expressions. By replacing unused local variables in a code base with _ their intention is conveyed very clearly. It clearly communicates to anyone reading a code snippet that the variable is not used elsewhere. Until now, this intention could only be communicated via comments, which, unfortunately, all developers don’t write.

Happy Coding!

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in Java, Access modifiers help to restrict the scope of a class, constructor, variable, method, or data member. It provides security, accessibility, etc to the user depending upon the access modifier used with the element. Let us learn about Java Access Modifiers, their types, and the uses of access modifiers in this article.

Types of Access Modifiers in Java

There are four types of access modifiers available in Java: 

• Default – No keyword required

1. Default Access Modifier

When no access modifier is specified for a class, method, or data member – It is said to be having the default access modifier by default. The data members, classes, or methods that are not declared using any access modifiers i.e. having default access modifiers are accessible only within the same package .

In this example, we will create two packages and the classes in the packages will be having the default access modifiers and we will try to access a class from one package from a class of the second package.

2. Private Access Modifier

The private access modifier is specified using the keyword private . The methods or data members declared as private are accessible only within the class in which they are declared.

• Any other class of the same package will not be able to access these members.
• private means “only visible within the enclosing class”.
• protected means “only visible within the enclosing class and any subclasses”

Hence these modifiers in terms of application to classes, apply only to nested classes and not on top-level classes

In this example, we will create two classes A and B within the same package p1. We will declare a method in class A as private and try to access this method from class B and see the result.

3. Protected Access Modifier

The protected access modifier is specified using the keyword protected .

The methods or data members declared as protected are accessible within the same package or subclasses in different packages.

In this example, we will create two packages p1 and p2. Class A in p1 is made public, to access it in p2. The method display in class A is protected and class B is inherited from class A and this protected method is then accessed by creating an object of class B.

Public Access modifier

The public access modifier is specified using the keyword public . 

• The public access modifier has the widest scope among all other access modifiers.
• Classes, methods, or data members that are declared as public are accessible from everywhere in the program. There is no restriction on the scope of public data members.

Important Points:

• If other programmers use your class, try to use the most restrictive access level that makes sense for a particular member. Use private unless you have a good reason not to.
• Avoid public fields except for constants.

Algorithm to use access modifier in Java

Here’s a basic algorithm for using access modifiers in Java: Define a class: Create a class that represents the object you want to manage. Define instance variables: Within the class, define instance variables that represent the data you want to manage. Specify an access modifier: For each instance variable, specify an access modifier that determines the visibility of the variable. The three main access modifiers in Java are private, protected, and public. Use private for variables that should only be accessible within the class: If you want to prevent access to a variable from outside the class, use the private access modifier. This is the most restrictive access modifier and provides the greatest level of encapsulation. Use protected for variables that should be accessible within the class and its subclasses : If you want to allow access to a variable from within the class and its subclasses, use the protected access modifier. This is less restrictive than private and provides some level of inheritance. Use public for variables that should be accessible from anywhere : If you want to allow access to a variable from anywhere, use the public access modifier. This is the least restrictive access modifier and provides the least amount of encapsulation. Use accessor and mutator methods to manage access to the variables: In order to access and modify the variables, use accessor (getter) and mutator (setter) methods, even if the variables have a public access modifier. This provides a level of abstraction and makes your code more maintainable and testable.

FAQs in Access Modifiers

1. what are access modifiers in java.

Access modifiers in Java are the keywords that are used for controlling the use of the methods, constructors, fields, and methods in a class.

2. What is void in Java?

Void in Java is used to specify no return value with the method.

3. What are the 12 modifiers in Java?

12 Modifiers in Java are public, private, protected, default, final, synchronized, abstract, native, strictfp, transient, and volatile.

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Published 05 Apr, 2024 under Release Notes

ESLint v9.0.0 released

We just pushed ESLint v9.0.0, which is a major release upgrade of ESLint. This release adds some new features and fixes several bugs found in the previous release. This release also has some breaking changes, so please read the following closely.

This is a summary of the significant changes, both breaking and non-breaking, you need to know about when upgrading from ESLint v8.x to ESLint v9.0.0.

Because this is a major release, you may not automatically be upgraded by npm. To ensure you are using this version, run:

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Node.js < v18.18.0, v19 no longer supported

As of this post, Node.js v20.x is the LTS release, and as such we are dropping support for all versions of Node.js prior to v18.18.0 as well as v19.x.

Flat config is now the default and has some changes

Flat config is now the default configuration format for ESLint and eslintrc is officially deprecated. To continue using a eslintrc configuration file, you’ll need to set the ESLINT_USE_FLAT_CONFIG environment variable to false .

This change affects users, plugin developers, and integrators as many aspects of ESLint had to change to make this happen. Please see our previous blog post for more details.

This release also introduces the config inspector , which can be launched on the command line using --inspect-config .

Removed all formatters except stylish , html , json , and json-with-meta

The following formatters have been removed:

• visualstudio

If you are using these formatters currently, you’ll need to install the standalone packages for use with ESLint v9.0.0.

Removed valid-jsdoc and require-jsdoc rules

We have removed valid-jsdoc and require-jsdoc . We recommend using the eslint-plugin-jsdoc plugin instead.

Removed deprecated methods on context and SourceCode

As we announced in September , we have removed a lot of deprecated methods from context and replaced them with methods on SourceCode .

Updated eslint:recommended

The eslint:recommended configuration is updated to include new rules that we feel are important, and to remove deprecated and less important rules.

New rule: no-useless-assignment

ESLint v9.0.0 introduces a new rule, no-useless-assignment , that is designed to catch situations where you’ve assigned a value to a variable and that value is never used. For example:

Updates to existing rules

• The complexity rule now also takes into account optional chaining and default values in destructuring patterns and parameters.
• The no-fallthrough rule has a new option reportUnusedFallthroughComment .
• The no-inner-declarations rule has a new default behavior. In v8.x, the rule would flag any functions defined inside of blocks as errors because this behavior was undefined in early versions of JavaScript. As of ES 2015, block-scoped function declarations are well-defined and so we changed the default behavior to not warn on block-scoped functions.
• The no-misleading-character-class rule now highlights the offending characters in a regular expression rather than the entire regular expression.
• The no-restricted-imports rule changed the behavior of paths . In v8.x, if multiple entries in the paths array of your configuration for The no-restricted-imports rule had the same name property, only the last one would apply. In v9.0.0, all entries apply, allowing for specifying different error messages for different imported names.
• The no-restricted-imports rule has new options allowImportNames and allowImportNamePattern .
• The no-unused-vars rule varsIgnorePattern option no longer applies to caught error variables.
• The no-unused-vars rule has a new default value for the caughtErrors option (changed from "none" to "all" ).
• The no-unused-vars rule has a new option ignoreClassWithStaticInitBlock .
• The no-unused-vars rule has a new option reportUsedIgnorePattern .
• The no-useless-computed-key rule has a new default value for the enforceForClassMembers option (changed from false to true ). This is intended to help avoiding misleading comments that can occur as a result of refactoring. When this option is set to true , the rule will prohibit a fallthrough comment if a case can never fallthrough.

New API loadESLint()

ESLint now exports a new function loadESLint() from its main entry point. Integrations can use this function to get either the ESLint class (former FlatESLint class) or the LegacyESLint class (former ESLint class) and thus easily swap between flat config and eslintrc APIs.

Changes to how you write rules

We’ve made multiple changes to help prevent errors in rules:

• Function-style rules will stop working in v9.0.0. Function-style rules are rules created by exporting a function from a file rather than exporting an object with a create() method.
• When a rule doesn’t have meta.schema specified, a default schema of [] will be applied. This means that rules without a schema will be assumed to have no options, which in turn means that validation will fail if options are provided.

Stricter RuleTester validations

This release adds more checks in RuleTester :

• Messages cannot have unsubstituted placeholders.
• Suggestions must change the code.
• Suggestion messages must be unique for the same lint problem.
• Suggestions must generate valid syntax.
• Test case output must be different from code .
• Test error objects must specify message or messageId .
• Test error object must specify suggestions if the actual error provides suggestions.
• Test suggestion objects must specify desc or messageId .
• Test suggestion objects must specify output .
• filename and only properties of test objects must be of the expected type ( string and boolean , respectively).
• Duplicate tests cause an error.

The --output-file flag now guarantees a file is output

The --output-file CLI flag is designed to output the results of the ESLint run to specified file. Prior to this release, no file would be output if linting passed with no errors or warnings. In v9.0.0, an empty file will be output when linting passes without any errors or warnings.

Better scope analysis

In v9.0.0, we updated the behavior of eslint-scope to fix a couple of longstanding bugs:

• Previously, ESLint would treat ("use strict") as a strict mode directive even though it is not. We fixed the behavior so only valid strict mode directives are honored.
• The containing scope of a class extends clause was incorrectly set to be the scope containing the class when it should have been the class scope itself. This has been fixed.

CodePath#currentSegments removed

As announced in our previous post , CodePath#currentSegments has been removed from the rules API. Please refer to the post for more details.

Precalculated Code Paths

ESLint v9.0.0 now precalculates code path information before the traversal used by rules. As a result, the code path information is now complete regardless of where it is accessed inside of a rule.

Multiple /* eslint */ comments for the same rule are now disallowed

In ESLint v8.x, if the file being linted contained multiple /* eslint */ configuration comments for the same rule, the last one would be applied, while the others would be silently ignored.

In ESLint v9.0.0, the first one is applied, while the others are reported as lint errors.

--quiet option is more performant

The --quiet option hides all warnings in the ESLint console. In v9.0.0, we are making a performance improvement by also not executing any rules set to "warn" .

Running eslint with no file arguments

If you are using flat config and you don’t pass any file arguments to the CLI, the CLI will default to linting the current directory , which means you can type npx eslint and it will just work. (Doing the same with an eslintrc config file will result in an error.)

Unused disable directives cause warnings by default

ESLint has long been able to flag unused disable directives. In this release, we’ve enabled warnings for unused disable directives by default. You can modify this value in your config file with linterOptions.reportUnusedDisableDirectives or on the command line using --report-unused-disable-directives-severity .

Performance statistics available in formatters via --stats

The information from the rule profiler is now available inside of formatters when the --stats flag is used in the CLI. This allows anyone to create custom visualizations of the performance information that ESLint tracks.

Breaking Changes

• b7cf3bd fix!: correct camelcase rule schema for allow option ( #18232 ) (eMerzh)
• 09bd7fe feat!: move AST traversal into SourceCode ( #18167 ) (Nicholas C. Zakas)
• 79a95eb feat!: disallow multiple configuration comments for same rule ( #18157 ) (Milos Djermanovic)
• 9163646 feat!: Rule Tester checks for missing placeholder data in the message ( #18073 ) (fnx)
• 3c4d51d feat!: default for enforceForClassMembers in no-useless-computed-key ( #18054 ) (Francesco Trotta)
• 47e60f8 feat!: Stricter rule test validations ( #17654 ) (fnx)
• 1a94589 feat!: no-unused-vars default caughtErrors to ‘all’ ( #18043 ) (Josh Goldberg ✨)
• 57089cb feat!: no-restricted-imports allow multiple config entries for same path ( #18021 ) (Milos Djermanovic)
• 2e1d549 feat!: detect duplicate test cases ( #17955 ) (Bryan Mishkin)
• 701f1af feat!: no-inner-declaration new default behaviour and option ( #17885 ) (Tanuj Kanti)
• bde5105 fix!: handle --output-file for empty output when saving to disk ( #17957 ) (Nitin Kumar)
• 07107a5 fix!: upgrade [email protected] ( #17942 ) (Milos Djermanovic)
• 3ee0f6c fix!: no-unused-vars varsIgnorePattern behavior with catch arguments ( #17932 ) (Tanuj Kanti)
• 51f8bc8 fix!: configuration comments with just severity should retain options ( #17945 ) (Milos Djermanovic)
• d191bdd feat!: Remove CodePath#currentSegments ( #17936 ) (Milos Djermanovic)
• 946ae00 feat!: FlatRuleTester -> RuleTester ( #17922 ) (Nicholas C. Zakas)
• baff28c feat!: remove no-inner-declarations from eslint:recommended ( #17920 ) (Milos Djermanovic)
• cadfbcd feat!: Rename FlatESLint to ESLint ( #17914 ) (Nicholas C. Zakas)
• d1018fc feat!: skip running warnings in --quiet mode ( #17274 ) (Maddy Miller)
• fb81b1c feat!: Set default schema: [] , drop support for function-style rules ( #17792 ) (Milos Djermanovic)
• 0b21e1f feat!: add two more cases to no-implicit-coercion ( #17832 ) (Gürgün Dayıoğlu)
• 2916c63 feat!: Switch Linter to flat config by default ( #17851 ) (Nicholas C. Zakas)
• 200518e fix!: Parsing ‘exported’ comment using parseListConfig ( #17675 ) (amondev)
• bdd6ba1 feat!: Remove valid-jsdoc and require-jsdoc ( #17694 ) (Nicholas C. Zakas)
• 12be307 fix!: Behavior of CLI when no arguments are passed ( #17644 ) (Nicholas C. Zakas)
• 8fe8c56 feat!: Update shouldUseFlatConfig and CLI so flat config is default ( #17748 ) (Nicholas C. Zakas)
• 60dea3e feat!: deprecate no-new-symbol , recommend no-new-native-nonconstructor ( #17710 ) (Francesco Trotta)
• 5aa9c49 feat!: check for parsing errors in suggestion fixes ( #16639 ) (Bryan Mishkin)
• b3e0bb0 feat!: assert suggestion messages are unique in rule testers ( #17532 ) (Josh Goldberg ✨)
• e563c52 feat!: no-invalid-regexp make allowConstructorFlags case-sensitive ( #17533 ) (Josh Goldberg ✨)
• e5f02c7 fix!: no-sequences rule schema correction ( #17878 ) (MHO)
• 6ee3e9e feat!: Update eslint:recommended configuration ( #17716 ) (Milos Djermanovic)
• c2cf85a feat!: drop support for string configurations in flat config array ( #17717 ) (Milos Djermanovic)
• c314fd6 feat!: Remove SourceCode#getComments() ( #17715 ) (Milos Djermanovic)
• ae78ff1 feat!: Remove deprecated context methods ( #17698 ) (Nicholas C. Zakas)
• f71c328 feat!: Swap FlatESLint-ESLint, FlatRuleTester-RuleTester in API ( #17823 ) (Nicholas C. Zakas)
• 5304da0 feat!: remove formatters except html, json(-with-metadata), and stylish ( #17531 ) (Josh Goldberg ✨)
• e1e827f feat!: Require Node.js ^18.18.0 || ^20.9.0 || >=21.1.0 ( #17725 ) (Milos Djermanovic)
• d54a412 feat: Add --inspect-config CLI flag ( #18270 ) (Nicholas C. Zakas)
• 97ce45b feat: Add reportUsedIgnorePattern option to no-unused-vars rule ( #17662 ) (Pearce Ropion)
• 3e9fcea feat: Show config names in error messages ( #18256 ) (Nicholas C. Zakas)
• de40874 feat: Rule Performance Statistics for flat ESLint ( #17850 ) (Mara Kiefer)
• d85c436 feat: use-isnan report NaN in indexOf and lastIndexOf with fromIndex ( #18225 ) (Tanuj Kanti)
• b8fb572 feat: add reportUnusedFallthroughComment option to no-fallthrough rule ( #18188 ) (Kirk Waiblinger)
• 1c173dc feat: add ignoreClassWithStaticInitBlock option to no-unused-vars ( #18170 ) (Tanuj Kanti)
• a451b32 feat: make no-misleading-character-class report more granular errors ( #18082 ) (Francesco Trotta)
• c49ed63 feat: update complexity rule for optional chaining & default values ( #18152 ) (Mathias Schreck)
• 11144a2 feat: no-restricted-imports option added allowImportNames ( #16196 ) (M Pater)
• 74124c2 feat: add suggestions to use-isnan in indexOf & lastIndexOf calls ( #18063 ) (StyleShit)
• 53f0f47 feat: Add loadESLint() API method for v9 ( #18097 ) (Nicholas C. Zakas)
• 2d11d46 feat: add suggestions to use-isnan in binary expressions ( #17996 ) (StyleShit)
• 26093c7 feat: fix false negatives in no-this-before-super ( #17762 ) (Yosuke Ota)
• 5471e43 feat: convert unsafe autofixes to suggestions in no-implicit-coercion ( #17985 ) (Gürgün Dayıoğlu)
• e3051be feat: emit warning when .eslintignore file is detected ( #17952 ) (Nitin Kumar)
• a630edd feat: maintain latest ecma version in ESLint ( #17958 ) (Milos Djermanovic)
• b4e0503 feat: add no-useless-assignment rule ( #17625 ) (Yosuke Ota)
• 287c4b7 feat: no-misleading-character-class granular errors ( #17515 ) (Josh Goldberg ✨)
• 8792464 feat: Enable eslint.config.mjs and eslint.config.cjs ( #17909 ) (Nicholas C. Zakas)
• 24ce927 feat: warn by default for unused disable directives ( #17879 ) (Bryan Mishkin)
• 610c148 fix: Support using declarations in no-lone-blocks ( #18269 ) (Kirk Waiblinger)
• e508800 fix: rule tester ignore irrelevant test case properties ( #18235 ) (fnx)
• a129acb fix: flat config name on ignores object ( #18258 ) (Nicholas C. Zakas)
• dadc5bf fix: constructor-super false positives with loops ( #18226 ) (Milos Djermanovic)
• ae8103d fix: load plugins in the CLI in flat config mode ( #18185 ) (Francesco Trotta)
• e37153f fix: improve error message for invalid rule config ( #18147 ) (Nitin Kumar)
• af6e170 fix: stop linting files after an error ( #18155 ) (Francesco Trotta)
• 0cb4914 fix: validate options when comment with just severity enables rule ( #18133 ) (Milos Djermanovic)
• c4d26fd fix: use-isnan doesn’t report on SequenceExpression s ( #18059 ) (StyleShit)
• 39076fb fix: handle absolute file paths in RuleTester ( #17989 ) (Nitin Kumar)
• 6d11f3d fix: Ensure config keys are printed for config errors ( #17980 ) (Nicholas C. Zakas)
• 806f708 fix: no-misleading-character-class edge cases with granular errors ( #17970 ) (Milos Djermanovic)
• f182114 fix: deep merge behavior in flat config ( #17906 ) (Francesco Trotta)
• b577e8a fix: allow circular references in config ( #17752 ) (Francesco Trotta)

Documentation

• e151050 docs: update get-started to the new @eslint/create-config ( #18217 ) (唯然)
• 94178ad docs: mention about name field in flat config ( #18252 ) (Anthony Fu)
• 1765c24 docs: add Troubleshooting page ( #18181 ) (Josh Goldberg ✨)
• 96607d0 docs: version selectors synchronization ( #18260 ) (Milos Djermanovic)
• 651ec91 docs: remove /* eslint-env */ comments from rule examples ( #18249 ) (Milos Djermanovic)
• 950c4f1 docs: Update README (GitHub Actions Bot)
• 12f5746 docs: add info about dot files and dir in flat config ( #18239 ) (Tanuj Kanti)
• b93f408 docs: update shared settings example ( #18251 ) (Tanuj Kanti)
• 26384d3 docs: fix ecmaVersion in one example, add checks ( #18241 ) (Milos Djermanovic)
• 7747097 docs: Update PR review process ( #18233 ) (Nicholas C. Zakas)
• b07d427 docs: fix typo ( #18246 ) (Kirill Gavrilov)
• 778082d docs: add Glossary page ( #18187 ) (Josh Goldberg ✨)
• 239a7e2 docs: Clarify the description of sort-imports options ( #18198 ) (gyeongwoo park)
• 4769c86 docs: fix incorrect example in no-lone-blocks ( #18215 ) (Tanuj Kanti)
• 5251327 docs: Update README (GitHub Actions Bot)
• 1dc8618 docs: Update README (GitHub Actions Bot)
• ba1c1bb docs: Update README (GitHub Actions Bot)
• 337cdf9 docs: Explain limitations of RuleTester fix testing ( #18175 ) (Nicholas C. Zakas)
• c7abd89 docs: Explain Node.js version support ( #18176 ) (Nicholas C. Zakas)
• d961eeb docs: show red underlines in examples in rules docs ( #18041 ) (Yosuke Ota)
• 558274a docs: Update README (GitHub Actions Bot)
• 2908b9b docs: Update release documentation ( #18174 ) (Nicholas C. Zakas)
• 1f1260e docs: replace HackerOne link with GitHub advisory ( #18165 ) (Francesco Trotta)
• e5ef3cd docs: add inline cases condition in no-fallthrough ( #18158 ) (Tanuj Kanti)
• 450d0f0 docs: fix ignore option docs ( #18154 ) (Francesco Trotta)
• 5fe095c docs: show v8.57.0 as latest version in dropdown ( #18142 ) (Milos Djermanovic)
• 7db5bb2 docs: Show prerelease version in dropdown ( #18135 ) (Nicholas C. Zakas)
• 73a5f06 docs: Update README (GitHub Actions Bot)
• f95cd27 docs: Disallow multiple rule configuration comments in the same example ( #18116 ) (Milos Djermanovic)
• d8068ec docs: Update link for schema examples ( #18112 ) (Svetlana)
• f1c7e6f docs: Switch to Ethical Ads ( #18090 ) (Strek)
• 15c143f docs: JS Foundation -> OpenJS Foundation in PR template ( #18092 ) (Nicholas C. Zakas)
• 6ea339e docs: add stricter rule test validations to v9 migration guide ( #18085 ) (Milos Djermanovic)
• 3c816f1 docs: use relative link from CLI to core concepts ( #18083 ) (Milos Djermanovic)
• 9458735 docs: fix malformed eslint config comments in rule examples ( #18078 ) (Francesco Trotta)
• 07a1ada docs: link from --fix CLI doc to the relevant core concept ( #18080 ) (Bryan Mishkin)
• b844324 docs: Update team responsibilities ( #18048 ) (Nicholas C. Zakas)
• aadfb60 docs: document languageOptions and other v9 changes for context ( #18074 ) (fnx)
• 857e242 docs: tweak explanation for meta.docs rule properties ( #18057 ) (Bryan Mishkin)
• 10485e8 docs: recommend messageId over message for reporting rule violations ( #18050 ) (Bryan Mishkin)
• 98b5ab4 docs: Update README (GitHub Actions Bot)
• 505fbf4 docs: update no-restricted-imports rule ( #18015 ) (Tanuj Kanti)
• c25b4af docs: Update README (GitHub Actions Bot)
• 33d1ab0 docs: add more examples to flat config ignores docs ( #18020 ) (Milos Djermanovic)
• e6eebca docs: Update sort-keys options properties count ( #18025 ) (LB (Ben Johnston))
• 1fedfd2 docs: Improve flat config ignores docs ( #17997 ) (Nicholas C. Zakas)
• 38b9b06 docs: update valid-typeof rule ( #18001 ) (Tanuj Kanti)
• b4abfea docs: Update note about ECMAScript support ( #17991 ) (Francesco Trotta)
• 6788873 docs: Update release blog post template ( #17994 ) (Nicholas C. Zakas)
• 1f37442 docs: Add sections on non-npm plugin configuration ( #17984 ) (Nicholas C. Zakas)
• 96307da docs: migration guide entry for no-inner-declarations ( #17977 ) (Tanuj Kanti)
• 40be60e docs: Update README (GitHub Actions Bot)
• d31c180 docs: fix number of code-path events on custom rules page ( #17969 ) (Richard Hunter)
• 1529ab2 docs: reorder entries in v9 migration guide ( #17967 ) (Milos Djermanovic)
• 9507525 docs: Explain how to combine configs ( #17947 ) (Nicholas C. Zakas)
• 7c78576 docs: Add more removed context methods to migrate to v9 guide ( #17951 ) (Milos Djermanovic)
• 3a877d6 docs: Update removed CLI flags migration ( #17939 ) (Nicholas C. Zakas)
• 4a9cd1e docs: Update Linter API for v9 ( #17937 ) (Milos Djermanovic)
• 2a8eea8 docs: update docs for v9.0.0-alpha.0 ( #17929 ) (Milos Djermanovic)
• 7f0ba51 docs: show NEXT in version selectors ( #17911 ) (Milos Djermanovic)
• 0a7911e docs: add flat config default to v9 migration guide ( #17927 ) (Milos Djermanovic)
• 94f8065 docs: Add CLI updates to migrate to v9 guide ( #17924 ) (Nicholas C. Zakas)
• 16187f2 docs: Add exported and string config notes to migrate to v9 guide ( #17926 ) (Nicholas C. Zakas)
• 3ae50cc docs: Add RuleTester changes to migrate to v9 guide ( #17923 ) (Nicholas C. Zakas)
• 0831b58 docs: add rule changes to v9 migration guide ( #17925 ) (Milos Djermanovic)
• 037abfc docs: update API docs ( #17919 ) (Milos Djermanovic)
• afc3c03 docs: add function-style and meta.schema changes to v9 migration guide ( #17912 ) (Milos Djermanovic)
• 1da0723 docs: update eslint:recommended section in Migrate to v9.x ( #17908 ) (Milos Djermanovic)
• f55881f docs: remove configuration-files-new.md ( #17907 ) (Milos Djermanovic)
• 63ae191 docs: Migrate to v9.0.0 ( #17905 ) (Nicholas C. Zakas)
• e708496 docs: Switch to flat config by default ( #17840 ) (Nicholas C. Zakas)
• fdf0424 docs: Update Create a Plugin for flat config ( #17826 ) (Nicholas C. Zakas)
• e6a91bd docs: Switch shareable config docs to use flat config ( #17827 ) (Nicholas C. Zakas)
• 3831fb7 docs: updated examples of max-lines rule ( #17898 ) (Tanuj Kanti)
• cd1ac20 docs: Update README (GitHub Actions Bot)

Build Related

• 26010c2 Build: changelog update for 9.0.0-rc.0 (Jenkins)
• b91f9dc build: fix TypeError in prism-eslint-hooks.js ( #18209 ) (Francesco Trotta)
• d7ec0d1 Build: changelog update for 9.0.0-beta.2 (Jenkins)
• fd9c0a9 Build: changelog update for 9.0.0-beta.1 (Jenkins)
• c9f2f33 build: changelog update for 8.57.0 ( #18144 ) (Milos Djermanovic)
• 1bbc495 Build: changelog update for 9.0.0-beta.0 (Jenkins)
• 96f8877 Build: changelog update for 9.0.0-alpha.2 (Jenkins)
• 52d5e7a Build: changelog update for 9.0.0-alpha.1 (Jenkins)
• c2bf27d build: update docs files when publishing prereleases ( #17940 ) (Milos Djermanovic)
• e91d85d Build: changelog update for 9.0.0-alpha.0 (Jenkins)
• 19f9a89 chore: Update dependencies for v9.0.0 ( #18275 ) (Nicholas C. Zakas)
• 7c957f2 chore: package.json update for @eslint/js release (Jenkins)
• d73a33c chore: ignore /docs/v8.x in link checker ( #18274 ) (Milos Djermanovic)
• 44a81c6 chore: upgrade knip ( #18272 ) (Lars Kappert)
• e80b60c chore: remove code for testing version selectors ( #18266 ) (Milos Djermanovic)
• a98babc chore: add npm script to run WebdriverIO test ( #18238 ) (Francesco Trotta)
• 9b7bd3b chore: update dependency markdownlint to ^0.34.0 ( #18237 ) (renovate[bot])
• 297416d chore: package.json update for eslint-9.0.0-rc.0 ( #18223 ) (Francesco Trotta)
• d363c51 chore: package.json update for @eslint/js release (Jenkins)
• 1b841bb chore: fix some comments ( #18213 ) (avoidaway)
• 29c3595 chore: remove repetitive words ( #18193 ) (cuithon)
• acc2e06 chore: Introduce Knip ( #18005 ) (Lars Kappert)
• 7509276 chore: upgrade @eslint/[email protected] ( #18180 ) (Milos Djermanovic)
• 96087b3 chore: package.json update for @eslint/js release (Jenkins)
• 925afa2 chore: Remove some uses of lodash.merge ( #18179 ) (Milos Djermanovic)
• 972ef15 chore: remove invalid type in @eslint/js ( #18164 ) (Nitin Kumar)
• 32ffdd1 chore: upgrade @eslint/[email protected] ( #18146 ) (Milos Djermanovic)
• e41425b chore: package.json update for @eslint/js release (Jenkins)
• bb3b9c6 chore: upgrade @eslint/[email protected] ( #18145 ) (Milos Djermanovic)
• e462524 chore: upgrade [email protected] ( #18138 ) (Milos Djermanovic)
• 8e13a6b chore: fix spelling mistake in README.md ( #18128 ) (Will Eastcott)
• 66f52e2 chore: remove unused tools rule-types.json, update-rule-types.js ( #18125 ) (Josh Goldberg ✨)
• bf0c7ef ci: fix sync-labels value of pr-labeler ( #18124 ) (Tanuj Kanti)
• cace6d0 ci: add PR labeler action ( #18109 ) (Nitin Kumar)
• 1a65d3e chore: export base config from eslint-config-eslint ( #18119 ) (Milos Djermanovic)
• 9aa4df3 refactor: remove globals dependency ( #18115 ) (Milos Djermanovic)
• e40d1d7 chore: upgrade @eslint/[email protected] ( #18108 ) (Milos Djermanovic)
• 9870f93 chore: package.json update for @eslint/js release (Jenkins)
• 2c62e79 chore: upgrade @eslint/[email protected] ( #18107 ) (Milos Djermanovic)
• 81f0294 chore: upgrade [email protected] ( #18106 ) (Milos Djermanovic)
• 5e2b292 chore: upgrade [email protected] ( #18105 ) (Milos Djermanovic)
• ce838ad chore: replace dependency npm-run-all with npm-run-all2 ^5.0.0 ( #18045 ) (renovate[bot])
• 54df731 chore: update dependency markdownlint-cli to ^0.39.0 ( #18084 ) (renovate[bot])
• 8f06a60 chore: update dependency shelljs to ^0.8.5 ( #18079 ) (Francesco Trotta)
• 93ffe30 chore: update dependency file-entry-cache to v8 ( #17903 ) (renovate[bot])
• 6ffdcbb chore: upgrade @eslint/[email protected] ( #18038 ) (Milos Djermanovic)
• 2c12715 chore: package.json update for @eslint/js release (Jenkins)
• cc74c4d chore: upgrade [email protected] ( #18037 ) (Milos Djermanovic)
• dfb68b6 chore: use Node.js 20 for docs sites ( #18026 ) (Milos Djermanovic)
• 8c1b8dd test: add more tests for ignoring files and directories ( #18018 ) (Milos Djermanovic)
• 60b966b chore: update dependency @eslint/js to v9.0.0-alpha.1 ( #18014 ) (renovate[bot])
• c893bc0 chore: update markdownlint to v0.33.0 ( #17995 ) (Nitin Kumar)
• c5e50ee chore: package.json update for @eslint/js release (Jenkins)
• 1bf2520 chore: Split Docs CI from core CI ( #17897 ) (Nicholas C. Zakas)
• 320787e chore: delete relative-module-resolver.js ( #17981 ) (Francesco Trotta)
• 4926f33 refactor: use Object.hasOwn() ( #17948 ) (Milos Djermanovic)
• df200e1 refactor: use Array.prototype.at() to get last elements ( #17949 ) (Milos Djermanovic)
• 750b8df chore: update dependency glob to v10 ( #17917 ) (renovate[bot])
• 74794f5 chore: removed unused eslintrc modules ( #17938 ) (Milos Djermanovic)
• 10ed29c chore: remove unused dependency rimraf ( #17934 ) (Francesco Trotta)
• 903ee60 ci: use --force flag when installing eslint ( #17921 ) (Milos Djermanovic)
• 17fedc1 chore: upgrade @eslint/[email protected] ( #17928 ) (Milos Djermanovic)
• cb89ef3 chore: package.json update for @eslint/js release (Jenkins)
• f6f4a45 chore: drop structuredClone polyfill for v9 ( #17915 ) (Kevin Gibbons)
• 412dcbb chore: upgrade [email protected] ( #17916 ) (Milos Djermanovic)
• 02a8baf chore: Rename files with underscores ( #17910 ) (Nicholas C. Zakas)
• c0f5d91 chore: remove creating an unused instance of Linter in tests ( #17902 ) (Milos Djermanovic)
• 3826cdf chore: use jsdoc/no-multi-asterisks with allowWhitespace: true ( #17900 ) (Percy Ma)
• a9a17b3 chore: fix getting scope in tests ( #17899 ) (Milos Djermanovic)
• 595a1f6 test: ensure that CLI tests run with FlatESLint ( #17884 ) (Francesco Trotta)
• c7eca43 chore: update dependency markdownlint-cli to ^0.38.0 ( #17865 ) (renovate[bot])
• cc0c9f7 ci: bump github/codeql-action from 2 to 3 ( #17873 ) (dependabot[bot])

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From the blog

The latest ESLint news, case studies, tutorials, and resources.

Introducing ESLint Config Inspector

Introducing the ESLint Config Inspector, a visual tool to help you understand and inspect ESLint flat configuration files.

ESLint v9.0.0-rc.0 released

We just pushed ESLint v9.0.0-rc.0, which is a major release upgrade of ESLint. This release adds some new features and fixes several bugs found in the previous release. This release also has some breaking changes, so please read the following closely.

ESLint v9.0.0-beta.2 released

We just pushed ESLint v9.0.0-beta.2, which is a major release upgrade of ESLint. This release adds some new features and fixes several bugs found in the previous release. This release also has some breaking changes, so please read the following closely.