Casting
In Java polymorphism is the ability of an object to take many forms.
/**
* In Java the object can be different types (polymorphism).
*
* To access a subtype method from a super type object ...
* you must cast the object with subtype.
*/
package com.minte9.oop.polymorphism;
public class Casting {
public static void main(String[] args) {
Animal a1 = new Dog(); // reference is an Animal
Animal a2 = new Cat(); // object is a Cat
System.out.println(a1.roaming());
System.out.println(a2.eating());
System.out.println((
(Dog) a1).barking() // Look Here
);
// myDog is roaming (super method)
// myCat is eating (super method)
// myDog is barking (Dog method)
}
}
class Animal {
protected String name;
public String eating() {
return name + " is eating (super method)";
}
public String roaming() {
return name + " is roaming (super method)";
}
}
class Dog extends Animal {
public Dog() {
name = "myDog";
}
public String barking() {
return name + " is barking (Dog method)";
}
}
class Cat extends Animal {
public Cat() {
name = "myCat";
}
}
Parameter
You can declare the method parameter as a super-class type.
/**
* Polymorphism and Dependency Injection
*
* Using polymorphism we can pass object as parameters ...
* and call object's super methods.
*/
package com.minte9.oop.polymorphism;
public class Parameter {
public static void main(String[] args) {
File file = new File();
Csv csv = new Csv();
Xml xml = new Xml();
file.open(csv); // CSV opened
file.open(xml); // XML opened
}
}
class Item {
protected String type;
public void open() {
System.out.println(type + " opened"); // PO
}
}
class Csv extends Item {
public Csv() {
type = "CSV";
}
}
class Xml extends Item {
public Xml() {
type = "XML";
}
}
class File {
public void open(Item item) { // DI
item.open();
}
}
Last update: 303 days ago
