Interface in java

An interface can contain:

public constants;
abstract methods without an implementation (the keyword abstract is not required here);
default methods with implementation (the keyword default is required);
static methods with implementation (the keyword static is required);
private methods with implementation.
Java 9 onwards, you can include private methods in interfaces. Before Java 9 
it was not possible.
An interface can't contain fields (only constants), constructors,
 or non-public abstract methods.
The keyword abstract before a method means that the method does not have a
body, it just declares a signature.

Interface in java

In many cases, it is more important to know what an object can do,instead of 
how it does what it does. This is a reason why interfaces are commonly used for
declaring a type of variable.
 interface : DrawingTool : a tool can draw
 interface DrawingTool {
    void draw(Curve curve);
}
DrawingTool pencil = new Pencil();
DrawingTool brush = new Brush();
Both Pencil and brush class should implement draw method

Interface in java

the main idea of an interface is declaring functionality.
Suppose you program a game that has several types of characters.
These characters are able to move within a map. That is represented by Movable
interface

Interface in java

interface Interface {
        
    int INT_CONSTANT = 0; // it's a constant, the same as public static final int INT_FIELD = 0
        
    void instanceMethod1();
        
    void instanceMethod2();
        
    static void staticMethod() {
        System.out.println("Interface: static method");
    }
        
    default void defaultMethod() {
        System.out.println("Interface: default method. It can be overridden");
    }

    private void privateMethod() {
        System.out.println("Interface: private methods in interfaces are acceptable but should have a body");
    }
}
Static, default, and private methods should have an implementation in the interface!

Interface in java

An interface is a special kind of class that cannot be instantiated.
 The main idea of an interface is declaring functionality. Interfaces help to 
 abstract from specific classes and emphasize the functionality. 
It makes software design more reusable and clean
Opposite to a class, an interface can extend several interfaces. 
A class can implement multiple interfaces.

Interface in java

/* File name : Animal.java */
interface Animal {
   public void eat();
   public void travel();
}

-1

Source: tutorialspoint.com

Similar codes

67 votes161 views3 answers
For javascipt
Java
0 vote141 views1 answer
How to check that letter is not a number and is repeating or not in a sentence in java
Java
16 votes170 views5 answers
Converting char array to string
Java
1 vote173 views1 answer
How to close the fragment by a close button in android
Java
1 vote191 views1 answer
String by byte array in java
Java
0 vote161 views1 answer
64 encode java
Java
0 vote156 views1 answer
Can strings be used in a 2 dimensional array in java
Java
0 vote160 views1 answer
Send HTTP Get Request with Parameters.
Java
2 votes156 views2 answers
Upcasting in java
Java
1 vote156 views1 answer
Failed to apply plugin [class 'com.google.gms.googleservices.GoogleServicesPlugin']
Java