Java - Inheritance

public class Animal{
}

public class Mammal extends Animal{
}

public class Reptile extends Animal{
}

public class Dog extends Mammal{
}

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Example:

public class Dog extends Mammal{

   public static void main(String args[]){

      Animal a = new Animal();
      Mammal m = new Mammal();
      Dog d = new Dog();

      System.out.println(m instanceof Animal);
      System.out.println(d instanceof Mammal);
      System.out.println(d instanceof Animal);
   }
}

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true
true
true

						
Example:

public interface Animal {}

public class Mammal implements Animal{
}

public class Dog extends Mammal{
}

						
The instanceof Keyword:

interface Animal{}

class Mammal implements Animal{}

public class Dog extends Mammal{
   public static void main(String args[]){

      Mammal m = new Mammal();
      Dog d = new Dog();

      System.out.println(m instanceof Animal);
      System.out.println(d instanceof Mammal);
      System.out.println(d instanceof Animal);
   }
} 

						

true
true
true

						
HAS-A relationship:

public class Vehicle{}
public class Speed{}
public class Van extends Vehicle{
	private Speed sp;
} 

						

public class extends Animal, Mammal{}