Java環境構築(Adoptium(旧:AdoptOpenJDK))

/**
 * The HelloWorldApp class implements an application that
 * simply prints "Hello World!" to standard output.
 */
class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}

$ javac HelloWorldApp.java

$ java HelloWorldApp

Hello World!

/* text */
The compiler ignores everything from /* to */.
/** documentation */
This indicates a documentation comment (doc comment, for short). The compiler ignores this kind of comment, just like it ignores comments that use /* and */. The javadoc tool uses doc comments when preparing automatically generated documentation. For more information on javadoc, see the Javadoc™ tool documentation .
// text
The compiler ignores everything from // to the end of the line.

class name {
    . . .
}

public static void main(String[] args)