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Unnamed Classes and Instance Main Methods

JEP-445

  • Ever found Java's "Hello, World!" program a bit too complex?

  • Java's complexity can be daunting for beginners.

  • No more unnecessary clutter in simple programs.

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Classic Approach

Classic Hello, World! program that is often used as the first program for Java students:

public class HelloWorld { 
    static String greeting = "Hello, World!";

    public static void main(String[] args) {
        System.out.println(String.format(":%s\n:%s\n:%s", HelloWorld.class.getName(), greeting,
                "Subscribe us on youtube.com/@semusings"));        
    }
}

java --source 22 --enable-preview HelloWorld.java

In this approach -> too much code, too many concepts, too many constructs

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Mordern Approach

Allow to lunch instance main methods. Such methods are not static, need not be public, and need not have a String[] parameter.

class HelloWorldUsingInstanceMethod {

    String greeting = "Hello, World!";

    void main() {
        System.out.println(String.format(":%s\n:%s\n:%s", getClass().getName(), greeting,
                "Subscribe us on youtube.com/@semusings"));
    }

}

java --source 22 --enable-preview HelloWorldUsingInstanceMethod.java
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Mordern Approach (contd.)

Unnamed classes to make the class declaration implicit

String greeting = "Hello, World!";

void main() {
    System.out.println(String.format(":%s\n:%s\n:%s", getClass().getName(), greeting,
            "Subscribe us on youtube.com/@semusings"));
}

java --source 22 --enable-preview HelloWorldUsingUnnamedClass.java
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Thank You!

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References