----------------------------------要是以后写数据库的产品，不是写SQL语句，那里面涉及到的锁就跟多了。
故事里有五个哲学家
这些哲学家很穷，只买得起五根筷子。他们坐成一圈，两个人的中间放一根筷子。哲学家吃饭的时候必须同时得到左手边和右手边的筷子。如果他身边的任何一位正在使用筷子，那他只有等着。
假设哲学家的编号是A、B、C、D、E，筷子编号是1、2、3、4、5，红色的是哲学家的手，哲学家和筷子围成一圈如下图所示：
实例235 门锁打不开了(死锁)_demo
实例236 门锁终于被打开了（解决死锁）
public class DoorOpen {
static String[] keys = new String[]{"第1把钥匙","第2把钥匙"};
static class DoorKey1 extends Thread{
public void run(){
synchronized(keys[0]){
System.out.println("我拿起了" + keys[0] + ",在等着朋友用" + keys[1] + "开防盗门");
try{
Thread.sleep(100);
}catch(Exception e){
System.out.println("线程休眠出错:" + e.getMessage());
}
synchronized(keys[1]){
System.out.println("我又拿出来"+ keys[1] + "打开了防盗门");
}
}
}
}
static class DoorKey2 extends Thread { // 静态内部类
public void run() {
synchronized(keys[0]){
System.out.println("\n朋友拿出了" + keys[0] + ",在等待我用" + keys[1]
+ "开防盗门");
try{
Thread.sleep(100);
}catch (Exception e) {
System.out.println("线程休眠出错：" + e.getMessage());
}
synchronized(keys[1]){
System.out.println("朋友又拿出了" + keys[1] + "打开了防盗门");
}
}
}
}
static class GoWrong extends Thread { // 静态守护线程类
public GoWrong(){
this.setDaemon(true); // 线程设置守护
}
public void run() {
while (true) {
try {
Thread.sleep(1000); // 线程休眠
} catch (Exception e) { // 捕获异常
System.out.println("线程休眠出错：" + e.getMessage());
}
System.out.println("守护线程：程序正在运行...");
}
}
}
public static void main(String[] args) { // java程序主入口处
DoorKey1 one = new DoorKey1(); // 实例化对象
DoorKey2 two = new DoorKey2();
GoWrong daemon = new GoWrong();
one.start(); // 启动线程
two.start();
daemon.start();
}
}
实例237 一个死锁的例子
import java.awt.*;
import java.awt.event.*;
public class DeadLock extends Frame{
protected static final String[] names = {"One", "Two"};
private int accounts[] = { 1000, 1000 };// 存入账号accounts
// 创建TextArea组件
private TextArea info = new TextArea(5,40);
private TextArea status = new TextArea(5,40);
public DeadLock(){
super("致命的死锁！");// 调用父类Frame的带参构造方法
this.setLayout(new GridLayout(2,1));
add(makePanel(info, "账号"));
add(makePanel(status, "线程"));
validate(); //validate验证
pack();
show();
// 创建DeadLockThread对象
DeadLockThread A = new DeadLockThread(0, this, status);
DeadLockThread B = new DeadLockThread(1, this, status);
this.addWindowListener(new WindowAdapter() { // 添加单击事件监听 WindowAdapter 窗口适配器
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
}
public synchronized void transfer(int from, int into, int amount) {// 转账transfer
info.append("\n账户 One:{1}quot; + accounts[0]);// 将给定文本追加到文本区的当前文本
info.append("\n账户 Two:{1}quot; + accounts[1]);
info.append("\n>={1}quot; + amount + "从" + names[from]+ "到" + names[into]);
while (accounts[from]<amount) {
try{
wait();
}catch(InterruptedException e){
e.printStackTrace();
}
accounts[from] = amount; //账户金额(取]= $金额;
accounts[into] = amount; //金额帐户 [到]=金额帐户;
notify(); //notify(); 通知();
}
}
private Panel makePanel(TextArea ta, String title){ // 创建面板，按选择的布局方式将组件进行布局
Panel p = new Panel();
p.setLayout(new BorderLayout());
p.add("North", new Label(title));
p.add("Center", ta);
return p;
}
public static void main(String[] args) {// 本程序的主方法
DeadLock dl = new DeadLock();
}
}
class DeadLockThread extends Thread {// 死锁线程
private DeadLock dl;
private int id;
private TextArea display; //TextArea 文字区域
public DeadLockThread(int _id, DeadLock _dl, TextArea _display) {
dl = _dl;
id = _id;
display = _display;
start();
}
public void run() {
while (true) {
int amount = (int) (2000 * Math.random());
display.append("\nTread" + DeadLock.names[id] + "将 {1}quot; + amount
+ "存入" + DeadLock.names[(1 - id)]);
try {
sleep(20);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
dl.transfer(id, 1 - id, amount);
}
}
}
