create abstract method and override java code example

Example 1: override abstract method java

public interface Order
{
    public boolean greaterThan(Order other);
}

public class AirCraft implements Order
{
   private String make;
   private int numSeats;

   public AirCraft(String make, int numSeats)
   {
      this.make = make;
      this.numSeats = numSeats;
   }

   public String getMake()
   {
      return make;
   }

   public int getNumSeats()
   {
      return numSeats;
   }

   @Override
   public boolean greaterThan(Order other)
   {
      AirCraft x = (AirCraft)other;
      return getNumSeats() > x.getNumSeats();
   }
   
   public String toString()
   {
       return make + " -> " + numSeats;
   }
}

Example 2: write a program in which an abstract class is being defined containg an abstract method omputer(int a, int b) and a non abstract method as well

abstract class Sum{
   
   public abstract int compute(int a, int b);
   public void disp(){
	System.out.println("Method of class Sum");
   }
}
class Demo extends Sum{

   public int compute(int a, int b){
	return a+b;
   }
   public static void main(String args[]){
	Sum obj = new Demo();
	System.out.println(obj.compute(3, 7));
	obj.disp();
   }
}