//AppletApp.java
import java.applet.Applet;              //Nhap thu vien chua lop Applet
import java.awt.Graphics;               //Nhan thu vien chua lop Graphics
//Moi chuong trinh applet deu phai mo rong (Extends), ke thua tu lop Applet
public class AppletApp extends Applet
    {
    CharStack stack;                    //Khai bao bien stack la bien kieu doi tuong CharStack
    String dayGoc, dayNguoc;
    //Nap chong lai ham init() de thuc hien khi nap va thuc hien applet
    public void init()
        {                               //(1)
        stack = new CharStack(80);      //Khoi tao stack
        dayGoc = new String("maN teiV ,ioN aH");
        int leng = dayGoc.length();     //So ky tu trong chuoi
    //Dat cac ky tu cua dayGoc vao stack de sau do lay ra theo thu tu nguoc lai
        for(int k = 0; k < leng; k++)   //Dua vao stack
            stack.push(dayGoc.charAt(k));
    //Doc ra tu stack theo thu tu dao nguoc va luu vao dayNguoc
        dayNguoc = new String();        //Chuoi moi rong
        while(!stack.isEmpty())
            dayNguoc+=stack.pop();
        }
    //Nap chong ham paint() de hien thi (ve) cac thong bao cua applet
    public void paint(Graphics g)
        {                               //(2)
        g.drawString("Day ky tu dao nguoc:",25,25);
        g.drawString(dayNguoc,25,25);
        }
    }
class CharStack
    {
    private char[] stackArray;          //Mang cac ky tu
    private int topOfStack;             //Dinh cua stack
    private static int counter;
    //Toan tu tao lap doi tuong
    public CharStack(int capacity)
        {
        stackArray = new char[capacity];
        topOfStack = -1;
        counter++;
        }
    public void push(char e)
        {
        stackArray[++topOfStack] = e;
        }
    public char pop()
        {
        return stackArray[topOfStack--];
        }
    public char peek()
        {
        return stackArray[topOfStack];
        }
    public boolean isEmpty()
        {
        return topOfStack < 0;
        }
    public boolean isFull()
        {
        return (topOfStack ==stackArray.length -1);
        }
    }