// The Stack ADT -- array implementation. Illustrates 
// how to declare, throw and catch exceptions.

import java.io.*;
import java.lang.RuntimeException;

public interface Stack2 {

   public void push (int item) throws StackFullException;
   public int pop() throws StackEmptyException;
   public int size();
   public boolean empty();
   public boolean full();
   public int ontop() throws StackEmptyException;

}

class StackEmptyException extends Exception {

   public StackEmptyException (String message) {
     System.out.println (message);
   }
}

class StackFullException extends Exception {

   public StackFullException (String message) {
     System.out.println (message);
   }
}

class StackADTv2 implements Stack2 {

   final int MAXSIZE = 100;   // by default, the stack contains
   private int size;          // 100 elements if no stack size
   private int[] stackADT;    // is specified
   private int top = -1;

   public StackADTv2 () {
     size = MAXSIZE;
     stackADT = new int[size];
   }

   public StackADTv2 (int inputsize) {
     size = inputsize;
     stackADT = new int[size];
   }

   public boolean empty () {
     return (top == -1);
   }

   public boolean full () {  
     return (top == size - 1);
   }

   public void push (int number) throws StackFullException {

     if (size() == size)
        throw new StackFullException ("The stack is full.");
     top++;
     stackADT[top] = number;
   }

   public int pop () throws StackEmptyException {

     if (empty())
        throw new StackEmptyException ("The stack is empty.");
     int i = stackADT[top];
     top--;
     return i;
   }

   public int ontop () throws StackEmptyException {

     if (empty())
        throw new StackEmptyException ("The stack is empty.");
     int i = pop();

     try {
       push(i);
     }
     catch (StackFullException e) {
        System.out.println ("The stack is full.");
     }

     return i;
   }

   public int size () {
     return (top + 1);
   }

}

class StackAppl2 {

   public static void main (String[] args) throws IOException {

     BufferedReader stdin = new BufferedReader 
            (new InputStreamReader(System.in));

     System.out.print ("Enter stack size: ");
     System.out.flush();
     int size = Integer.parseInt(stdin.readLine());

     StackADTv2 stack = new StackADTv2(size);

     int i = 2;

     /* catching two exceptions, StackFullException and 
        StackEmptyException */

     try {
       for (int j = 1; j <= 7; j++) {
          stack.push(i);
          System.out.println (stack.ontop() + " pushed");
          i = i + 2;
       }
     }
     catch (StackFullException e) {
         System.out.println ("The stack is full.");
     }
     catch (StackEmptyException e) {
         System.out.println ("The stack is empty.");
     }

     System.out.println ("The current stack contains " + stack.size() +
             " elements.");

     try {
       for (int j = 1; j <= 7; j++) {
          System.out.println (stack.pop() + " poped");
       }
     }
     catch (StackEmptyException e) {
         System.out.println ("The stack is empty.");
     }

   }
}