Interfaces In Java

  Program to illustrate the concept of Interfaces

package com.company;
interface bycycle{
    void speed();// you can only initialize methods in interfaces
    void brake();// you can't declare any method in interfaces
}
interface code{
    void cls();
}
class cycle implements bycycle { //implement keyword for the interfaces
    @Override
    public void brake() {       //you must declare all the methods of interfaces
                                // or it will show error
        System.out.println("decrement the speed");
    }
    @Override
    public void speed() {
        System.out.println("increment the speed");
    }
    public void xls(){
        System.out.println("hy I'm class object");//you can add methods to class
    }
}
public class interfaces {
    public static void main(String[] args) {
        cycle c= new cycle();
        c.brake();
        c.speed();
        c.xls();
    }
}

program to use two different interfaces in single class and also use inheritance in same class

package com.company;
interface bycycle{
    void speed();// you can only initialize methods in interfaces
    void brake();// you can't declare any method in interfaces
}
interface code{
    void cls();
}
class class2{// you can also extend the class using inheritance in interfaces
    public void object(){
        System.out.println("hy, I'm class2's object");
    }
}
class cycle extends class2 implements bycycle, code {  
    //implement keyword for the interfaces
    @Override
    // here i used two different interfaces in single class i.e.(bycycle and code)
    public void brake() {
        System.out.println("decrement the speed");
    }
    @Override
    public void speed() {
        System.out.println("increment the speed");
    }
    public void xls(){
        System.out.println("hy I'm class object");
    }
    public void cls(){
        System.out.println("hy, I'm second interface");
    }
}
public class interfaces {
    public static void main(String[] args) {
        cycle c= new cycle();
        c.brake();      //interface1 object1
        c.speed();      //interface2 object2
        c.xls();        //child class object
        c.cls();        //interface2 object
        c.object();     //parent class object
    }
}

program to illustrate the concept of default keyword in Interface

package com.company;
interface car{
    void drive();
}
interface truck{
    void Load();
    // 'default' keyword is used it initialize object in interface
    //this helps if you have lots of classes, there is no need to initialize same object again and again
    //you just need to call the object with class reference
    default void tyres(){
        System.out.println("repair all tyres before going");
    }
}
class vehicle implements car,truck{
    public void drive(){
        System.out.println("driving car in highway");
    }
    public void Load(){
        System.out.println("loading things in truck");
    }
}
public class defaultMETHODS {
    public static void main(String[] args) {
        vehicle v= new vehicle();
        v.tyres();
        v.drive();
        v.Load();
    }
}

Inheritance in interfaces

package com.company;
interface sample{
    void method1();
    void method2();
}
interface sample1 extends sample{
    void method3();
    void method4();
}
class random implements sample1{
    public void method1(){
        System.out.println("Hy, I'm method 1");
    }
    public void method2(){
        System.out.println("Hy, I'm method 2");
    }
    public void method3(){
        System.out.println("Hy, I'm method 3");
    }
    public void method4(){
        System.out.println("Hy, I'm method 4");
    }
}
public class inheritanceINinterfaces {
    public static void main(String[] args) {
        random r= new random();
        r.method1();
        r.method2();
        r.method3();
        r.method4();
    }
}