Implement a stack from a LinkedList in Java

A stack can be implemented using a LinkedList by managing the LinkedList as a stack. This is done by using a class Stack which contains some of the Stack methods such as push(), top(), pop() etc.

A program that demonstrates this is given as follows −

Example

 Live Demo

import java.util.LinkedList;
class Stack {
   private LinkedList l = new LinkedList();
   public void push(Object obj) {
     l.addFirst(obj);
   }
   public Object top() {
      return l.getFirst();
   }
   public Object pop() {
      return l.removeFirst();
   }
}
public class Demo {
   public static void main(String[] args) {
      Stack s = new Stack();
      s.push(5);
      s.push(1);
      s.push(3);
      s.push(9);
      s.push(7);
      System.out.println("The top element of the stack is: " + s.top());
      System.out.println("The stack element that is popped is: " + s.pop());
      System.out.println("The stack element that is popped is: " + s.pop());
      System.out.println("The top element of the stack is: " + s.top());
   }
}

Output

The top element of the stack is: 7
The stack element that is popped is: 7
The stack element that is popped is: 9
The top element of the stack is: 3

Now let us understand the above program.

A class Stack is created which contains some of the Stack methods such as push(), top(), pop() etc. A code snippet which demonstrates this is as follows −

class Stack {
   private LinkedList l = new LinkedList();
   public void push(Object obj) {
      l.addFirst(obj);
   }
   public Object top() {
      return l.getFirst();
   }
   public Object pop() {
      return l.removeFirst();
   }
}

In the method main(), an object s is created of the class Stack. Then this is used to push elements into the stack, display the top element and pop elements from the stack. A code snippet which demonstrates this is as follows −

public static void main(String[] args) {
   Stack s = new Stack();
   s.push(5);
   s.push(1);
   s.push(3);
   s.push(9);
   s.push(7);
   System.out.println("The top element of the stack is: " + s.top());
   System.out.println("The stack element that is popped is: " + s.pop());
   System.out.println("The stack element that is popped is: " + s.pop());
   System.out.println("The top element of the stack is: " + s.top());
}