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Another way to achieve abstraction in Java, is with interfaces
Another way to achieve abstraction in Java, is with interfaces.
An interface
is a completely "abstract class"
that is used to group related methods with empty bodies:
// interface
interface Animal {
public void animalSound(); // interface method (does not have a body)
public void run(); // interface method (does not have a body)
}
To access the interface methods, the interface must be "implemented"
(kinda like inherited) by another class with the implements
keyword (instead of extends
). The body of the
interface method is provided by the "implement" class:
// Interface
interface 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 interface
class 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();
}
}
abstract
and
public
public
,
static
and final
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 can implement multiple interfaces. Note: To implement multiple interfaces, separate them with a comma (see example below).
To implement multiple interfaces, separate them with a comma:
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();
}
}