Hello World!

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/**
 * 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.
    }
}

compile and run

javac HelloWorldApp.java
java HelloWorldApp

object, class, package

inheritance

class MountainBike extends Bicycle {
     // new fields and methods defining a mountain bike would go here
}

interface

class ACMEBicycle implements Bicycle {
// remainder of this class implemented as before
}

package