prettier-plugin-java

What is prettier-plugin-java?

The prettier-plugin-java npm package is a plugin for Prettier that formats Java code. It ensures that Java code adheres to a consistent style, making it easier to read and maintain.

What are prettier-plugin-java's main functionalities?

Code Formatting

This feature automatically formats Java code to follow a consistent style. For example, it ensures proper indentation, spacing, and line breaks.

public class HelloWorld {
  public static void main(String[] args) {
    System.out.println("Hello, World!");
  }
}

Consistent Style

This feature enforces a consistent coding style across the entire codebase, making it easier to read and maintain. It handles things like method spacing, bracket placement, and more.

public class Example {
  private int value;

  public int getValue() {
    return value;
  }

  public void setValue(int value) {
    this.value = value;
  }
}

Integration with Prettier

This feature allows the plugin to be easily integrated with Prettier, enabling seamless formatting of Java code alongside other languages supported by Prettier.

{
  "prettier": {
    "plugins": ["prettier-plugin-java"]
  }
}

Other packages similar to prettier-plugin-java

google-java-format

google-java-format is a program that reformats Java source code to comply with Google Java Style. It is similar to prettier-plugin-java in that it enforces a consistent style, but it specifically adheres to Google's style guide.

spotless

Spotless is a general-purpose code formatter that supports multiple languages, including Java. It can be configured to use different formatters, such as google-java-format or prettier-plugin-java, providing flexibility in formatting rules.

README

prettier-plugin-java

Prettier is an opinionated code formatter which forces a certain coding style. It makes the code consistent through an entire project.

This plugin allows the support of Java on Prettier.

The plugin implementation is pretty straightforward as it uses java-parser (thanks to Chevrotain) visitor to traverse the Concrete Syntax Tree and apply the format processing on each node (it uses Prettier API).

Installation

Pre-requirements

Since the plugin is meant to be used with Prettier, you need to install it:

npm install --save-dev --save-exact prettier

or

yarn add prettier --dev --exact

Install plugin

npm install prettier-plugin-java --save-dev

or

yarn add prettier-plugin-java --dev

CLI

If you installed Prettier globally and want to format java code via the CLI, run the following command:

npm install -g prettier-plugin-java

The plugin will be automatically loaded, check here for more.

Usage

CLI

prettier --write MyJavaFile.java

If the plugin is not automatically loaded:

# Example where the plugin is locate in node_modules
prettier --write MyJavaFile.java --plugin=./node_modules/prettier-plugin-java

API

const prettier = require("prettier");
const javaText = `
public class HelloWorldExample{
  public static void main(String args[]){
    System.out.println("Hello World !");
  }
}
`;

const formattedText = prettier.format(javaText, {
  parser: "java",
  tabWidth: 2
});

Example of formatted code

Input

public class HelloWorld {
public static void main(String[] args) {System.out.println("Hello World!");;;;;}

@Override
public String toString() {
  return "Hello World";
}
  public int sum(int argument1,int argument2,int argument3,int argument4,int argument5
  ) {
    return argument1+argument2+ argument3 +argument4  + argument5;
  }
}

Output

public class HelloWorld {

  public static void main(String[] args) {
    System.out.println("Hello World!");
  }

  @Override
  public String toString() {
    return "Hello World";
  }

  public int sum(
    int argument1,
    int argument2,
    int argument3,
    int argument4,
    int argument5
  ) {
    return argument1 + argument2 + argument3 + argument4 + argument5;
  }
}

Options

We added a custom option entrypoint in order to run prettier on code snippet.

Usage

prettier --write MyJava.java --entrypoint compilationUnit
Here is the exhaustive list of all entrypoints.

Example

MyJavaCode.java content:

public void myfunction() {
    mymethod.is().very().very().very().very().very().very().very().very().very().very().very().very().very().very().big();
}

Run:
prettier --write MyJavaCode.java --entrypoint classBodyDeclaration

Result:

public void myfunction() {
  mymethod
    .is()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .very()
    .big();
}

Changelog

v1.2.0

Enhancements

• Supports of instance of pattern matching (#476)

// Input
if (o instanceof Integer i || p instanceof Point || q instanceof Circle c || r instanceof Square) {
  formatted = String.format("int %d", i);
} else if (o instanceof Long l) {
  formatted = String.format("long %d", l);
} else if (o instanceof Double d) {
  formatted = String.format("double %f", d);
} else if (o instanceof String s) {
  formatted = String.format("String %s", s);
}

// Output
if (
  o instanceof Integer i ||
  p instanceof Point ||
  q instanceof Circle c ||
  r instanceof Square
) {
  formatted = String.format("int %d", i);
} else if (o instanceof Long l) {
  formatted = String.format("long %d", l);
} else if (o instanceof Double d) {
  formatted = String.format("double %f", d);
} else if (o instanceof String s) {
  formatted = String.format("String %s", s);
}

• Supports of sealed classes and interfaces (#478)

// Input
public sealed class Rectangle implements Shape permits Square {

  private final double length;
  private final double height;

  public Rectangle(double length, double height) {
    this.length = length;
    this.height = height;
  }

  @Override
  public double area() {
    return length * height;
  }
}

// Output
public sealed class Rectangle implements Shape permits Square {

  private final double length;
  private final double height;

  public Rectangle(double length, double height) {
    this.length = length;
    this.height = height;
  }

  @Override
  public double area() {
    return length * height;
  }
}

Miscellaneous

• Add copy/pastable Checkstyle configuration compatible with Prettier (#477)