加密与解密原理的一个例子

　　package lockunlock;

import Java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import java.util.*;
public class LockUnlock extends JApplet {
private boolean isStandalone = false;
//Get a parameter value
public String getParameter(String key, String def) {
return isStandalone ? System.getProperty(key, def) :
(getParameter(key) != null ? getParameter(key) : def);
}

//ConstrUCt the applet
public LockUnlock() {
}
//Initialize the applet
public void init() {
try {
jbInit();
}
catch(Exception e) {
e.printStackTrace();
}
}
//Component initialization
private void jbInit() throws Exception {
contentPane = (JPanel) this.getContentPane();
jLabel1.setText("String");
jLabel1.setBounds(new Rectangle(35, 36, 57, 21));
contentPane.setLayout(null);
this.setSize(new Dimension(400, 300));
jLabel2.setText("String length");
jLabel2.setBounds(new Rectangle(29, 73, 69, 22));
jTextField1.setText("");
jTextField1.setBounds(new Rectangle(108, 40, 166, 17));
jTextField2.setText("");
jTextField2.setBounds(new Rectangle(107, 72, 56, 21));
jButton1.setBounds(new Rectangle(30, 236, 137, 27));
jButton1.setText("Exercise 3");
jButton1.addActionListener(new LockUnlock_jButton1_actionAdapter(this));
jButton2.setBounds(new Rectangle(218, 237, 131, 27));
jButton2.setText("Exercise 4");
jButton2.addActionListener(new LockUnlock_jButton2_actionAdapter(this));
jTextField3.setText("");
jTextField3.setBounds(new Rectangle(106, 105, 58, 21));
jLabel3.setText("MoShu");
jLabel3.setBounds(new Rectangle(36, 106, 86, 18));
contentPane.add(jLabel1, null);
contentPane.add(jButton2, null);
contentPane.add(jButton1, null);
contentPane.add(jLabel3, null);
contentPane.add(jTextField2, null);
contentPane.add(jLabel2, null);
contentPane.add(jTextField3, null);
contentPane.add(jTextField1, null);

}
//Get Applet information
public String getAppletInfo() {
return "Applet Information";
}
//Get parameter info
public String[][] getParameterInfo() {
return null;
}
//Main method
public static void main(String[] args) {
LockUnlock applet = new LockUnlock();
applet.isStandalone = true;
JFrame frame = new JFrame();
//EXIT_ON_CLOSE == 3
frame.setDefaultCloseOperation(3);
frame.setTitle("Applet Frame");
frame.getContentPane().add(applet, BorderLayout.CENTER);
applet.init();
applet.start();
frame.setSize(400,320);
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation((d.width - frame.getSize().width) / 2, (d.height - frame.getSize().height) / 2);
frame.setVisible(true);
}

//static initializer for setting look & feel
static {
try {
//UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
//UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
}
catch(Exception e) {
}
}
//Declare DataMember
int index;

//-----------------------------------------------------
JPanel contentPane;
JLabel jLabel1 = new JLabel();
JLabel jLabel2 = new JLabel();
JTextField jTextField2 = new JTextField();
JTextField jTextField1 = new JTextField();
JButton jButton1 = new JButton();
JButton jButton2 = new JButton();
JTextField jTextField3 = new JTextField();
JLabel jLabel3 = new JLabel();

//----------------------N!------------------------------
public int function(int N){
if(N==1)
return 1;
else{
return N*function(N-1);
/*不是RETURN function(N-1);
而是 N*function(N-1);*/
}
}
//-----------用递归法求一个串的全排列-----------------------
public void Arrange(String prefix,String suffix,int[] Array){
String newPrefix,newSuffix;
int numOfChars =suffix.length();
if(numOfChars==1){
Array[index]=Integer.parseInt(prefix+suffix);
index++;
}
else{
for(int i=1; i<=numOfChars;i++){
newSuffix=suffix.substring(1,numOfChars);
newPrefix=prefix+suffix.charAt(0);
Arrange(newPrefix,newSuffix,Array);
suffix=newSuffix+suffix.charAt(0);
}
}
}
//----------Arrange From the Min to the Max------------------
/*public void RankForArrange(int[] Array){
int bottom=Array.length-1 ;
int temp;
for(int i=bottom;i>0;i--){
for(int j=0;j<i;j++){
if(Array[j]>Array[j+1]){
temp =Array[j];
Array[j] =Array[j+1];
Array[j+1]=temp;
}
}
}
}
*/
//-------------------Find the aim number----------------------
public int FindAim(int aim,int[] Array){
boolean isFound=false;
int location=0;
int length=Array.length ;
for(int i=0;i<length;i++){
if(Array[i]==aim){
location=i;
isFound =true;
}
}
if(isFound)
return location;
else
System.out.println("Not Found");
return location;
/*在if里return 不行吗？*/
}

//------------------Creat String-------------------------------
public String CreatString(int length){
StringBuffer BufString=new StringBuffer();
for(int i=1;i<=length;i++){
BufString.append(i) ;
}
return BufString.toString();
}
//-----------OutPut Result--------------------
public void OutPutResult1(){
index = 0; //clear to 0
String AimString, prefix;
AimString = jTextField1.getText();
int Length = AimString.length();
String strLength = String.valueOf(Length);
int Aim = Integer.parseInt(AimString);
/* 方法.parseInt才是转换为int类型
而不是.getInteger*/
int[] EachArrange = new int[this.function(Length)];
jTextField2.setText(strLength);
prefix = ""; //Make an empty String
if (AimString.length() > 2 &&
AimString.length() < 9 && AimString != "") {
Arrange(prefix, AimString, EachArrange);
//RankForArrange(EachArrange);
Arrays.sort(EachArrange);
String result = String.valueOf(FindAim(Aim, EachArrange));
jTextField3.setText(result);
}
else {
System.out.println("Your String is too short");
}
}

//----------Out put result 2---------------------
public void OutPutRestlt2(){
index=0;//Let index come back to 0
String strLength, strMoShu,
AimString, prefix,suffix;
int Length, MoShu,limit;
strLength = jTextField2.getText();
strMoShu = jTextField3.getText();
Length = Integer.parseInt(strLength);
MoShu = Integer.parseInt(strMoShu);
limit = function(Length);
int[] EachArrange = new int[this.function(Length)];
if (Length > 2&&Length<9&&
strLength!=""&&strMoShu!=""
&&MoShu<limit) {
prefix = "";
suffix =CreatString(Length);
Arrange(prefix, suffix, EachArrange);
Arrays.sort(EachArrange);
String strResult=String.valueOf(EachArrange[MoShu]);
jTextField1.setText(strResult);
}
else
System.out.println("Input Ouf MoShu, Try again") ;
}

void jButton1_actionPerformed(ActionEvent e) {
this.OutPutResult1();
}

void jButton2_actionPerformed(ActionEvent e) {
this.OutPutRestlt2();
}
//-----------------------------------------------------------

}

class LockUnlock_jButton1_actionAdapter implements java.awt.event.ActionListener {
LockUnlock adaptee;

LockUnlock_jButton1_actionAdapter(LockUnlock adaptee) {
this.adaptee = adaptee;
}
public void actionPerformed(ActionEvent e) {
adaptee.jButton1_actionPerformed(e);
}
}

class LockUnlock_jButton2_actionAdapter implements java.awt.event.ActionListener {
LockUnlock adaptee;

LockUnlock_jButton2_actionAdapter(LockUnlock adaptee) {
this.adaptee = adaptee;
}
public void actionPerformed(ActionEvent e) {
adaptee.jButton2_actionPerformed(e);
}
}