The following tutorial discusses issues with multiple inheritance and why java does not allow it. It also introduces interfaces
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Syntax for declaring interface
interface <interface_name>{
//methods
}
To use a interface in your class , append the keyword “implements” after your class name followed by the interface name
Ex
class Dog implements Pet
Points to note:
The class which implements the interface needsto provide functionality for the methods declared in the interface
All methods in an interface are implicitly public and abstract
An interface cannot be instantiated
An interface reference can point to objects of its implementing classes
An interface can extend from one or many interfaces. A class can extend only one class but implement any number of interfaces
interface RidableAnimal extends Animal, Vehicle
Assignment: To learn interfaces
Step 1) Copy following code into an editor.
interface Pet{
public void test();
}
class Dog implements Pet{
public void test(){
System.out.println("Interface Method Implemented");
}
public static void main(String args[]){
Pet p = new Dog();
p.test();
}
}
Step 2) Save , Compile & Run the code. Observe the Output.
Point to Ponder
While designing ,how do you choose between Abstract & Interface ?
Use an abstract class when a template needs to be defined for a group of subclasses
Use an interface when a role needs to be defined for other classes, regardless of the inheritance tree of these classes