Question

Java Generics (Javas built-in Stack)

What are the problems?

   class genStck {

        Stack stk = new Stack ();

        public void push(E obj) {           

             push(E);        

        }

        public E pop() {       

Object obj = pop();

        }

   }

  

    class Output {

        public static void main(String args[]) {

            genStck <> gs = new genStck ();

            push(36);

            System.out.println(pop());

        }

   }

Answer 1

HI,

Program:

import java.util.*;

//declare class with generic type <E>
class genStck<E> {
   Stack stk = new Stack();

   public void push(E obj) {
       stk.push(obj);
   }

   public E pop() {
       //return popped element
       return (E) stk.pop();
   }
}

//class with main method need to be public
public class Output {

   //main method
   public static void main(String args[]) {
       try {
           //we need to provide the Obect type in '<>'
           //like Integer/Double, String
           genStck<Integer> gs = new genStck<Integer>();
           gs.push(36);
           System.out.println(gs.pop());
       } catch (Exception e) {
           //printing errors if there any
           e.printStackTrace();
       }
   }
}

Output Screenshot: