class Stack2 {

   private int maxSize;        // size of stack array
   private long[] stackArray;
   private int top;            // top of stack
//--------------------------------------------------------------
   public Stack2(int s)         // constructor
      {
      maxSize = s;             // set array size
      stackArray = new long[maxSize];  // create array
      top = -1;                // no items yet
      }
//--------------------------------------------------------------
   public void push(long j) throws StackOverflowException
       // put item on top of stack
      {
      if( isFull() ) {
       throw new StackOverflowException( );
      } 
      stackArray[++top] = j;     // increment top, insert item
      }
//--------------------------------------------------------------
   public long pop() throws StackUnderflowException
              // take item from top of stack
      {
      if ( isEmpty() ) {
        throw new StackUnderflowException( );
      }
      return stackArray[top--];  // access item, decrement top
      }
//--------------------------------------------------------------
   public long peek()          // peek at top of stack
      {
      return stackArray[top];
      }
//--------------------------------------------------------------
   public boolean isEmpty()    // true if stack is empty
      {
      return (top == -1);
      }
//--------------------------------------------------------------
   public boolean isFull()     // true if stack is full
      {
      return (top == maxSize-1);
      } 
 }
 
 class StackOverflowException extends Exception
 {
 }
 
 class StackUnderflowException extends Exception
 {
 }
 
 class Stack2App {
  public static void main( String [] args ) {
    Stack2 stack = new Stack2(10);
    try {
      stack.push( 54 );
    }
    catch( StackOverflowException e ) {
      System.out.println( "Stack is full" );
    }
  }
 }