synchronized

1. 不能实现同步

每个对象有自己的锁。。。。、

public class ThreadTest extends Thread {
private int threadNo;
public ThreadTest(int threadNo) {
this.threadNo = threadNo;
}
public static void main(String[] args) throws Exception {
for (int i = 1; i < 10; i++) {
new ThreadTest(i).start();
Thread.sleep(1);
}
}
public synchronized void run() {
for (int i = 1; i < 10000; i++) {
System.out.println("No." + threadNo + ":" + i);
}
}
}


2.同步 ：

1.public class ThreadTest2 extends Thread {
private int threadNo;
private String lock;
public ThreadTest2(int threadNo, String lock) {
this.threadNo = threadNo;
this.lock = lock;
}
public static void main(String[] args) throws Exception {
String lock = new String("lock");
for (int i = 1; i < 10; i++) {
new ThreadTest2(i, lock).start();
Thread.sleep(1);
}
}
public void run() {
synchronized (lock) {
for (int i = 1; i < 10000; i++) {
System.out.println("No." + threadNo + ":" + i);
}
}
}
}

2.public class ThreadTest3 extends Thread {
private int threadNo;
private String lock;
public ThreadTest3(int threadNo, String lock) {
this.threadNo = threadNo;
this.lock = lock;
}
public static void main(String[] args) throws Exception {
String lock = new String("lock");
for (int i = 1; i < 20; i++) {
new ThreadTest3(i, lock).start();
Thread.sleep(1);
}
}
public static synchronized void abc(int threadNo) {
for (int i = 1; i < 10000; i++) {
System.out.println("No." + threadNo + ":" + i);
}
}
public void run() {
abc(threadNo);
}
}