synchronized同步机制的应用

public class TextThread {
/**
* 该程序是为了说明synchronized锁住对象的条件，
* 即同步的两个或多个线程必须是对同一对象上锁
* （不管是this表示的当前对象，还是其他定义的
* 对象如String对象等）
* 如果每个线程新建不同的对象，然后对不同对象上锁
* 如TxtThread tt0 = new TxtThread();TxtThread tt1 = new TxtThread();
* 然后对当前对象this上锁，将会失效。
*/
public static void main(String[] args) {
// TODO 自动生成方法存根
TxtThread tt0 = new TxtThread();
// TxtThread tt1 = new TxtThread();
// TxtThread tt2 = new TxtThread();
// TxtThread tt3 = new TxtThread();
tt0.flag = false;
new Thread(tt0).start();
TxtThread tt1 = new TxtThread();
//tt1.flag = true;
new Thread(tt0).start();
// new Thread(tt0).start();
// new Thread(tt0).start();
// new Thread(tt1).start();
// new Thread(tt2).start();
// new Thread(tt3).start();
}
}

class TxtThread implements Runnable {

static String str = new String();
boolean flag;

public void run() {
if (flag == true) {
for (int i = 1; i <= 20; i++) {
try {
Thread.sleep(10);
} catch (Exception e) {
e.getMessage();
}
System.out.println("鎖之外");
}
synchronized (this) {
int num = 100;
while (num > 0) {
try {
Thread.sleep(10);
} catch (Ex
aba2
ception e) {
e.getMessage();
}
System.out.println(Thread.currentThread().getName()
+ "this is 模块1 " + num--);
}
}
}
if (flag == false) {
synchronized (this) {

int num = 100;
while (num > 0) {
try {
Thread.sleep(10);
} catch (Exception e) {
e.getMessage();
}
System.out.println(Thread.currentThread().getName()
+ "this is模块2 " + num--);

}
}
}
}
}