Java Polymorphism.

Java Polymorphism

  • Polymorphism is the third essential feature of an object-oriented programming language, after data abstraction and inheritance.
  • Poly means many, and morph means form: A polymorphic function is many-formed.
  • Building polymorphism is :
    • The capability to bind specific derived class objects to base class reference at runtime.
    • Create Overriding methods to change the behavior of objects in the sub-classes (it is called subtype polymorphism).
    A polymorphism example:
    class Vehicle {
      static int wheels = 4;
      public String Status() {
        return "I am a Vehicle with " + wheels + " wheels";
    class Trailer extends Vehicle {
      static int wheels = 16; // this hides statics wheels in Vehicle
      public String Status() {
        return "I am a Trailer with " + wheels + "  wheels";
    public class PolymorphismDemo {
      public static void main(String args[]) {
        Vehicle a = new Vehicle();      // Vehicle reference to an Vehicle object
        Vehicle b = new Trailer();      // Vehicle reference to a Trailer object
        System.out.println(a.Status()); // Runs the method in Vehicle class
        System.out.println(b.Status()); // Runs the method in Trailer class
    The result of this is:
    I am a Vehicle with 4 wheels
    I am a Trailer with 16  wheels
    You can download this example here (needed tools can be found in the right menu on this page).
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