Interface in Java
Java Interface
Interfaces are like reference for the implementation of real time entities(class). Interface will have the methods and variables. The class implementing interface should use a keyword implements.
Note: Till java 1.7 – methods are abstract, public and variables are public, final, static.
Example: Mobile is the interface and the real time implementation of the interfaces will be done by the mobile manufactures.
interface Mobile{
int i=10;
public void call();
public void messaging();}
class SamsungS10 implements Mobile{
public void call(){
System.out.println(“call implementation”);
}
public void messaging(){
System.out.println(“messaging implementation”);
}
}
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From java 1.8 interfaces can have default methods and static methods
Default methods:
interface Mobile{
int i=10;
public void call();
public void messaging();
default void unlockMobile(){
System.out.println(“pattern”);
}
}
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No need of implementation of unlockMobile method:
class Lenovop1 implements Mobile{
public void call(){
System.out.println(“call implementation”);
}
public void messaging(){
System.out.println(“messaging implementation”);
}
}
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Implementing unlockMobile() method:
class Lenovop1 implements Mobile{
public void call(){
System.out.println(“call implementation”);
}
public void messaging(){
System.out.println(“messaging implementation”);
}
public void unlockMobile(){
System.out.println(“pattern or thumb impression”);
}
}
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Static Methods:
Same as default methods except we can call static methods by interface name directly.
interface Mobile{
int i=10;
public void call();
public void messaging();
static void unlockMobile(){
System.out.println(“pattern”);
}
}
Class User{
public static void main(String[] args){
Mobile.unlockMobile();
}
}
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interface InterfaceA{
default void defaultMethod(){
System.out.println(“interfaceA default method”)
}
}
interface InterfaceB{
default void defaultMethod(){
System.out.println(“interfaceB default method”)
}
}
class ImplementationClass implements InterfaceA,InterfaceB{
public void normalMethod(){
System.out.println(“normal method”);
}
}
class MainClass {
public static void main(String[] args){
ImplementationClass objImplementationClass = new ImplementationClass();
objImplementationClass.defaultMethod();
}
}
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Solution : Need to implement the default method or the static method in the implementation class when we are implementing two interfaces which have same signature for the default or static methods.
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