Java Interfaces Tutorial
An interface in Java is a blueprint of a class. It has static constants and abstract methods. The interface in Java is a mechanism to achieve abstraction. There can be only abstract methods in the Java interface, not method body.
Why use Java Interface?
- It is used to achieve abstraction.
- By interface, we can support the functionality of multiple inheritance.
- It can be used to achieve loose coupling.
Syntax
interface <interface_name> {
// declare constant fields
// declare methods that abstract
// by default.
}Java Interface Example
interface Drawable {
void draw();
}
class Rectangle implements Drawable {
public void draw() {
System.out.println("drawing rectangle");
}
}
class Circle implements Drawable {
public void draw() {
System.out.println("drawing circle");
}
}
class TestInterface1 {
public static void main(String args[]) {
Drawable d = new Circle();
d.draw();
}
}Java 8 Interface Improvements
Since Java 8, we can have default and static methods in an interface.
Default Method Example
interface Drawable {
void draw();
default void msg() {
System.out.println("default method");
}
}