Api.java

public interface Api {
    // constant declarations
    int CAFEBABE = 0xCAFEBABE;

    // abstract methods
    void foo(int data);

    void bar(int data);

    // default methods
    default void foo2(int data) {
        new Object() {
            void foo() {
                validate(data);
                System.out.println("I am foo v2!");
            }
        }.foo();
    }

    default void bar2(int data) {
        new Object() {
            void bar() {
                validate(data);
                System.out.println("I am bar v2!");
            }
        }.bar();
    }

    // static methods
    static String ping() {
        return "pong!";
    }

    // private methods
    private boolean validate(int data) {
        System.out.println("validating input: " + Integer.toHexString(data) + " => " + this);
        return true;
    }

    static void main(String[] args) {
        Api.ping();
        Api api = new Api() {
            @Override
            public void foo(int data) {
                System.out.println("I am legacy foo!");
            }

            @Override
            public void bar(int data) {
                System.out.println("I am legacy bar!");
            }
        };
        api.foo(CAFEBABE);
        api.bar(CAFEBABE);
        api.foo2(CAFEBABE);
        api.bar2(CAFEBABE);
    }
}