Abstract Classes in Java

I like abstract classes more then generic polymorphic classes or interfaces. I tend to view abstract classes somewhere in-between polymorphism and interfaces.

Here is a link to the java docs on abstract methods and classes.

If you looked at my Polymorphism in Java post this should like familiar to you. An abstract class works in the same fashion as a parent class in polymorphism but you can also reference undefined methods like in interfaces. The keyword in this code is “abstract”.

Here is my base class, Animal

package Abstract;

abstract class Animal {
	private String name;
	private Type type;
	public enum Type{
	public Animal(){
		this.name = null;
		this.type = Type.omnivor;
	public Animal(Type type){
		this.type = type;
	public String getName(){ return this.name; }
	public Type   getType(){ return this.type; }
	abstract public String speak();

Now let’s derive another class from the abstract class Animals. The keyword here like in poloymorphism is “extends”.

public class Duck extends Animal {

	public Duck(){
	public String speak() {

I also made another kind an animal and the code of the class is set up very much the same as the duck class.

package Abstract;

public class Cow extends Animal{
	public Cow(){
	public String speak() {
		return ("Moo");

Here is a simple test case on how to use the cow and duck objects.

package Abstract;

public class testAbstract {
	public static void main(String[] args){
		Cow myCow = new Cow();
		System.out.println("The cow says: " + myCow.speak() );
		Duck myDuck = new Duck();
		System.out.println( "The duck says: " + myDuck.speak() );

Sample output:
The cow says: Moo
The duck says: aflac


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