Example

// interfaceinterface Animal {  public void animalSound(); // interface method (does not have a body)  public void run(); // interface method (does not have a body)}

Example

// Interfaceinterface Animal {  public void animalSound(); // interface method (does not have a body)  public void sleep(); // interface method (does not have a body)}// Pig "implements" the Animal interfaceclass Pig implements Animal {  public void animalSound() {    // The body of animalSound() is provided here    System.out.println("The pig says: wee wee");  }  public void sleep() {    // The body of sleep() is provided here    System.out.println("Zzz");  }}class Main {  public static void main(String[] args) {    Pig myPig = new Pig();  // Create a Pig object    myPig.animalSound();    myPig.sleep();  }}

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Notes on Interfaces:

• Likeabstract classes, interfacescannot be used to create objects (in the example above, it is not possible to create an "Animal" object in the MyMainClass)
• Interface methods do not have a body - the body is provided by the "implement" class
• On implementation of an interface, you must override all of its methods
• Interface methods are by defaultabstract andpublic
• Interface attributes are by defaultpublic,static andfinal
• An interface cannot contain a constructor (as it cannot be used to create objects)

Why And When To Use Interfaces?

1) To achieve security - hide certain details and only show the important details of an object (interface).

2) Java does not support "multiple inheritance" (a class can only inherit from one superclass). However, it can be achieved with interfaces, because the class canimplement multiple interfaces.Note: To implement multiple interfaces, separate them with a comma (see example below).

Example

interface FirstInterface {  public void myMethod(); // interface method}interface SecondInterface {  public void myOtherMethod(); // interface method}class DemoClass implements FirstInterface, SecondInterface {  public void myMethod() {    System.out.println("Some text..");  }  public void myOtherMethod() {    System.out.println("Some other text...");  }}class Main {  public static void main(String[] args) {    DemoClass myObj = new DemoClass();    myObj.myMethod();    myObj.myOtherMethod();  }}

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