/**
 * Class CharStack is based on the StackX class from Robert LaFore's book,
 * "Data Structures and Algorithms in Java" published by the Waite Group Press.
 * This class creates a char array of the size passed to the constructor.
 * Each element in the stack array can hold one char value.
 * 
 * @author Robert LaFore, Modified by David Thibodeau
 * @version 16-July-2002
 */
public class CharStack
{
   private int    maxSize;    // size of stack array
   private char[] stackArray;
   private int    top;        // top of the stack

   /**
    * Constructor for objects of class CharStack
    */
   public CharStack(int s)
   {
      maxSize = s; // set array size
      stackArray = new char[maxSize]; // create array
      top = -1; // top indicator set to show no items in array yet
   }

   /**
    * push method - Pushes a char onto the stack
    * 
    * @param  c   the char to be pushed
    * @return void
    */
   public void push(char c)
   {
      stackArray[++top] = c; // increment top, insert char
   }
   
   /**
    * pop method - Pops a char off the stack and returns the
    * char value.
    * 
    * @param  void
    * @return char The value popped off the stack
    */
   public char pop()
   {
      return stackArray[top--]; // return char, decrement top
   }
   
   /**
    * push method - Pushes a char onto the stack
    * 
    * @param  c   the char to be pushed
    * @return void
    */
   public char peek()
   {
      return stackArray[top]; // return char at top of stack
   }
   
   /**
    * isEmpty method - Returns true is the stack is empty
    * 
    * @param  void
    * @return boolean - true if the stack is empty
    */
   public boolean isEmpty()
   {
      return (top == -1); // returns true if top equals -1
   }

   /**
    * isFull method - Returns true is the stack array is full
    * 
    * @param  void
    * @return boolean - true if the stack is full
    */
   public boolean isFull()
   {
      return (top == maxSize); // returns true if top equals maxSize of the array
   }
} // end Class CharStack


/////////////////////////////////////////////////////////////////////////////////
/**
 * Class StackGUI provides a front-end for the CharStack class. The user
 * enters a sentence into a textfield. Once entered, the user clicks the reverse
 * button and by using the stack, the order of the characters are reversed
 * and output into another TextField object.
 * 
 * @author David Thibodeau
 * @version 16-July-20002
 */
import java.awt.* ;
import java.awt.event.*;
import javax.swing.*;
    
public class StackGUI extends JFrame implements ActionListener
{
   // Sentence input panel
   JLabel     inputLabel;
   JTextField inputText;
   JButton    inputButton;
   JPanel     inputPanel;
      
   // Sentence output panel
   JLabel     outputLabel;
   JTextField outputText;
   JPanel     outputPanel;

   /**
    * Constructor for objects of class StackGUI
    * This will generate the GUI for the class StackGUI
    */
   public StackGUI()
   {
      setTitle( "Sentence Reverser" );
      setDefaultCloseOperation( EXIT_ON_CLOSE );
      
      // input group
      inputLabel  = new JLabel( "Enter your sentence here:" );
      inputText   = new JTextField(30); // Sets concurrent # of chars viewable to 30
      inputButton = new JButton( "Reverse" );
      inputButton.addActionListener(this);
      inputButton.setActionCommand( "Reverse" );
      
      inputPanel = new JPanel();
      inputPanel.add ( inputLabel );
      inputPanel.add ( inputText );
      inputPanel.add ( inputButton );
      
      // output group
      outputLabel = new JLabel ( "Reversed sentence appears here:" );
      outputText  = new JTextField(30);
      outputText.setEditable( false );
      
      outputPanel = new JPanel();
      outputPanel.add ( outputLabel );
      outputPanel.add ( outputText );
      
      // content pane
        getContentPane().setLayout(
                    new BoxLayout( getContentPane(), BoxLayout.Y_AXIS ) );
        getContentPane().add( inputPanel );
        getContentPane().add( outputPanel );
   }

   /**
    * actionPerformed method. This method handles the GUI click events
    * for the reverse button. When the button is clicked, the sentence
    * is pushed onto the stack object one char at a time. Once this is
    * complete, a while loop pops the stack until the isEmpty method
    * returns true. Once that happens, the output text is placed into
    * the outputText textfield.
    * @param ActionEvent supplied by Java's Swing event handler
    * @return void
    */
   public void actionPerformed( ActionEvent evt )
   {
      int stackSize;
      String sentence = "", reversed = "";
      CharStack theStack;
      
      if ( evt.getActionCommand().equals( "Reverse" ) )
      {
         sentence = inputText.getText();
         stackSize = sentence.length();
         theStack = new CharStack(stackSize);
         for(int i = 0; i < stackSize; i++)
         {
            theStack.push( sentence.charAt(i) );
         } // pushes all chars onto stack
         while( !theStack.isEmpty() )
         {
            reversed += theStack.pop();
         } // pops until isEmpty is true
         outputText.setText( reversed );
      }
   }
   
   /**
    * main method. This creates a new instance of StackGUI, then
    * instantiates a new WindowQuitter() object and lastly sets the
    * size and visibility of the GUI window.
    */
   public static void main ( String[] args )
   {
      // New GUI instance
      StackGUI stackApp  = new StackGUI();

      // New WindowQuitter instance
      WindowQuitter wquit = new WindowQuitter();
      stackApp.addWindowListener( wquit );

      // Set window size & make visible
      stackApp.setSize( 400, 200 );
      stackApp.setVisible( true );
   } // end main
} // end Class StackGUI


class WindowQuitter extends WindowAdapter
{
    public void windowClosing( WindowEvent e )
    {
        System.exit( 0 );  
    }
}