implements Java Keyword with Examples

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The implements keyword is used in a class declaration to indicate that the class being declared provides implementations for all methods declared in the interface whose name follows the implements keyword.

implements Java Keyword Example

The following example illustrates a class implements an interface and provides a detailed implementation for the interface's methods:

/**
 * This represents payment interface
 */
interface Payment {
    public void pay();
}

class CashPayment implements Payment {

    // method overriding
    @Override
    public void pay() {
        System.out.println("This is cash payment");
    }

}

class CreditPayment implements Payment {

    // method overriding
    @Override
    public void pay() {
        System.out.println("This is credit card payment");
    }
}

Unlike extends keyword, a class can implement multiple interfaces. The interface names are separated by commas. For example:

interface A {

}

interface B {

}

class C implements A, B {

}

Summary

1. A single class may implement multiple interfaces.
2. If the implemented class does not provide an implementation for the interface's methods, the class must be abstract.