Java多线程 synchronized锁的应用

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1.当变量被加上synchronized锁，同一时间只允许一个线程在synchronized内的代码块

2.被synchronized修饰的方法，相当于给方法上锁，同一时间只允许一个线程调用该方法

对于非静态方法，synchronized上锁的实际上是 this变量

对于静态方法，synchronized上锁的实际上是 Class变量比方Demo类，上锁的是Demo.class(表示Class变量)

package test;//4个窗口售票，每个窗口一个线程class Ticket implements Runnable {private static int tick = 100;Object mutex = new Object();public void run() {while (true) {//1.*****当变量(Object对象)被加上synchronized锁，只允许一个线程允许在synchronized内的代码块,如mutexsynchronized (mutex) { if (tick > 0) {try {Thread.sleep(10);} catch (InterruptedException e) {  // 复写Runnable的run方法,不提供异常抛出// TODO Auto-generated catch blocke.printStackTrace();}System.out.println(Thread.currentThread().getName()+ ".....Sale : " + tick--);}}}}public synchronized void show() {   //2.*****非静态成员方法,锁this变量if(tick > 0) {try {Thread.sleep(10);} catch (InterruptedException e) { // 复写Runnable的run方法,不提供异常抛出// TODO Auto-generated catch blocke.printStackTrace();}System.out.println(Thread.currentThread().getName()+ ".....Sale : " + tick--);}}public static synchronized void staticShow() { //3.*****静态成员方法,锁Class变量，这里是锁Ticket.classif(tick > 0) {try {Thread.sleep(10);} catch (InterruptedException e) { // 复写Runnable的run方法,不提供异常抛出// TODO Auto-generated catch blocke.printStackTrace();}System.out.println(Thread.currentThread().getName()+ ".....Sale : " + tick--);}}}public class TicketDemo {public static void main(String[] args) {Ticket t = new Ticket();Thread t1 = new Thread(t);  //t为Runnable的实现Thread t2 = new Thread(t);Thread t3 = new Thread(t);Thread t4 = new Thread(t);t1.start();t2.start();t3.start();t4.start();}}

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