Apr 13, 2012

Stack Class

Extends the Vector class. Used to create a simple last-in-first-out stack.
·         An item is stored on a stack by ‘pushing’ it into the stack.
·         An item may subsequently be ‘popped’ off the stack and used.
·         A Stack object will grow in size as new items are pushed onto it.
Example:
import java.util.EmptyStackException;
import java.util.Stack;
public class StackDemo {
    Stack s;
    public StackDemo()
    {
      s = new Stack();
    }
    public static void main(String args[])
    {
      StackDemo objStackDemo = new StackDemo();
      objStackDemo.pushItem("Harry");
      objStackDemo.pushItem("Emaini");
      objStackDemo.pushItem("Voldmort");
      objStackDemo.pushItem("Snape");
      objStackDemo.pushItem("Dumbuldore");
      System.out.println();
      objStackDemo.popItem();
      objStackDemo.popItem();
      objStackDemo.popItem();
      objStackDemo.popItem();
      objStackDemo.popItem();
      try
      {
          objStackDemo.popItem();
      } catch(EmptyStackException e) {
          System.out.println("Exception : Empty Stack");
          }
    }
    void pushItem(String str)
    {
      s.push(str);
      System.out.println("Pushed : " + str);
      System.out.println("Stack has : " + s);
    }
    void popItem()
    {
       String str = (String)s.pop();
       System.out.println("Popped : " + str);
       System.out.println("Stack has : " + s);
    }
}

Queue Interface
public interface Queue extends Collection
– A collection designed for holding elements prior to processing.
– Queues typically order elements in a FIFO (first-in-first-out) manner.
– In a FIFO queue, all new elements are inserted at the tail of the queue.

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