The Stack Class

Stack is a subclass of Vector that implements a standard last-in, first-out stack.

Stack only defines the default constructor, which creates an empty stack. Stack includes all the methods defined by Vector, and adds several of its own.

Stack( )

Apart from the methods inherited from its parent class Vector, Stack defines following methods:

SN	Methods with Description
1	boolean empty() Tests if this stack is empty. Returns true if the stack is empty, and returns false if the stack contains elements.
2	Object peek( ) Returns the element on the top of the stack, but does not remove it.
3	Object pop( ) Returns the element on the top of the stack, removing it in the process.
4	Object push(Object element) Pushes element onto the stack. element is also returned.
5	int search(Object element) Searches for element in the stack. If found, its offset from the top of the stack is returned. Otherwise, .1 is returned.

Example:

The following program illustrates several of the methods supported by this collection:

import java.util.*;

public class StackDemo {

   static void showpush(Stack st, int a) {

      st.push(new Integer(a));

      System.out.println("push(" + a + ")");

      System.out.println("stack: " + st);

   }

   static void showpop(Stack st) {

      System.out.print("pop -> ");

      Integer a = (Integer) st.pop();

      System.out.println(a);

      System.out.println("stack: " + st);

   }

   public static void main(String args[]) {

      Stack st = new Stack();

      System.out.println("stack: " + st);

      showpush(st, 42);

      showpush(st, 66);

      showpush(st, 99);

      showpop(st);

      showpop(st);

      showpop(st);

      try {

         showpop(st);

      } catch (EmptyStackException e) {

         System.out.println("empty stack");

      }

   }

}

This would produce following result:

stack: [ ]

push(42)

stack: [42]

push(66)

stack: [42, 66]

push(99)

stack: [42, 66, 99]

pop -> 99

stack: [42, 66]

pop -> 66

stack: [42]

pop -> 42

stack: [ ]

pop -> empty stack