Java Interface

tags

Interface

source

DT-On Java 8

Grammar

• don’t have to use abstract keyword
• after java 8, allow default methods (default implementation)
• after java 8, allow static methods
• can be public, if that interface is defined in a file of the same name
• methods are public, so implementation of derived classes’s methods must be public, too

public interface PureInterface {
    int m1();
    void m2();
    double m3();
}

Default Method

Define a default implementation for methods in interfaces. The compelling reason if default is that it allows new methods added without breaking all the code that uses that interface.

interface InterfaceWithDefault {
    void firstMethod();
    void secondMethod();
    default void newMethod() {
        System.out.println("newMethod");
    }
}