Introducing Multi-File Launch for Java - Simpler and Faster Execution of Interdependent Programs with JDK 22

Java 22 introduces a new feature that allows users to directly launch applications consisting of multiple source code files, without the need to explicitly compile them first. This simplifies the execution and distribution of small to medium Java programs, making the language more approachable for scripting and educational purposes.

An example of this new feature can be seen in a simple game called "Guess the Number". The program consists of three separate Java files: Main.java, Game.java, and Validator.java. The Main.java file acts as the entry point for the program and contains the main() method. It also imports the Game.java file, which contains the game logic, and the Validator.java file, which handles user input validation.

Before Java 22, in order to run this program, one would need to manually compile all three files in the correct order before executing the Main.java file. However, with the new feature, all three files can be executed together with a single command.

Main.java

	
// imports the "Game" and "Validator" files
import Game.java;
import Validator.java;

public class Main {
  public static void main(String[] args) {
    // creates a new instance of the "Game" class
    Game game = new Game();
    // calls the "startGame" method from the "Game" class
    game.startGame();
  }
}

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Game.java

	
// imports the "Validator" file
import Validator.java;

public class Game {
  // declares and initializes the "secretNumber" variable
  private int secretNumber = 7;
  
  public void startGame() {
    // invokes the "getGuess" method from the "Validator" class
    int guess = Validator.getGuess();
    // checks if the user's guess is equal to the secret number
    if (guess == secretNumber) {
      System.out.println("Congratulations, you guessed correctly!");
    } else {
      System.out.println("Sorry, that's not the number, try again!");
      // calls the "startGame" method again to give the user another chance to guess
      startGame();
    }
  }
}

‍

Validator.java

	
// imports the "Scanner" class for user input
import java.util.Scanner;

public class Validator {
  public static int getGuess() {
    // creates a new instance of the "Scanner" class
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter a number between 1 and 10:");
    // takes user input and returns it as an integer
    return Integer.parseInt(sc.nextLine());
  }
}

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With the new feature in Java 22, running this program is as simple as navigating to the folder containing all three files and executing the following command:

java Main.java
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This command will automatically compile and execute all three files together, eliminating the need to manually manage the compilation order. This results in a more streamlined and user-friendly experience, especially for beginners learning how to code in Java.

In summary, the new ability to launch multi-file source code programs directly in Java 22 makes the language more approachable for scripting and educational purposes. It simplifies the execution process and improves the usability of Java for small to medium scale programs. This enhancement showcases Java's continuous effort to improve its functionality and user experience for developers of all levels.

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