Java Anonymous Class Implementing an Interface Example

Java Nested Classes: Exercise-4 with Solution

Anonymous Class Exercise:
Write a Java program to create an interface called Greeting with a method sayHello(). In the main method, create an anonymous class that implements the Greeting interface and override the sayHello() method to print "Hello, World!". Call the sayHello() method.

Sample Solution:

Java Code:

Main.java

// Main class containing the main method
public class Main {
    public static void main(String[] args) {
        // Creating an anonymous class that implements the Greeting interface
        Greeting greeting = new Greeting() {
            @Override
            public void sayHello() {
                // Overriding the sayHello method to print "Hello, World!"
                System.out.println("Hello, World!");
            }
        };

        // Calling the sayHello method of the anonymous class
        greeting.sayHello();
    }
}

Output:

Hello, World!

Explanation:

• Interface Greeting: Defines a method sayHello() that must be implemented by any class that implements this interface.
• Main class: Contains the main method where the execution starts.
• Anonymous class: Implements the Greeting interface and overrides the sayHello() method to print "Hello, World!".
• Override sayHello(): Provides the implementation for the sayHello() method defined in the Greeting interface.
• Calling sayHello(): The overridden method is called to print the greeting message.

Note on Java Nested Classes:

• In this exercise, the Java nested classes concept is demonstrated through the use of an anonymous class.
• An anonymous class is a class without a name and is used to instantiate objects with certain modifications, such as implementing an interface or extending another class.
• This allows for concise and flexible code, particularly useful for implementing simple interfaces or abstract classes without cluttering the code with additional class definitions.
• The example shows how to implement the Greeting interface using an anonymous class.
• The anonymous class provides an implementation for the sayHello() method.
• The sayHello() method is invoked to display a greeting message.

Java Code Editor:

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