多线程编程实例
package thread;
public class TestSync implements Runnable{
Timer timer = new Timer();
public static void main(String args[]){
TestSync ts = new TestSync();
Thread t1 = new Thread(ts);
Thread t2 = new Thread(ts);
t1.setName("t1");
t2.setName("t2");
t1.start();
t2.start();
}
public void run(){
timer.add(Thread.currentThread().getName());
}
}
class Timer{
private static int num=0;
//没有synchronized关键字，执行结果：
//t1,你是第2个使用timer的线程!
//t2,你是第2个使用timer的线程!
//有synchronized关键字，执行结果：
//t1,你是第1个使用timer的线程!
//t2,你是第2个使用timer的线程!
//synchronized可以对需要同步执行的代码进行同步
//加在代码块上和方法上，那么同步的粒度将会发生改变
public synchronized void add(String name){
num++;
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(name+",你是第"+num+"个使用timer的线程!");
}
}
package thread;
public class DeadLockTest implements Runnable{
public int flag = 1;
static Object o1 = new Object(),o2 = new Object();
public void run() {
System.out.println("flag = "+ flag);
if(flag ==1){
synchronized(o1){
try {
System.out.println("lock o1,waitting for o2,sleeping......");
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized(o2){
System.out.println("1");
}
}
}
if(flag ==2){
synchronized(o2){
try {
System.out.println("lock o2,waitting for o1,sleeping......");
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized(o1){
System.out.println("2");
}
}
}
}//run block
public static void main(String args[]){
DeadLockTest dl1 = new DeadLockTest();
DeadLockTest dl2 = new DeadLockTest();
dl1.flag = 1;
dl2.flag = 2;
Thread t1 = new Thread(dl1);
Thread t2 = new Thread(dl2);
t1.start();
t2.start();
//程序一直处于挂起，等待状态。。。。。。
//flag = 1
//lock o1,waitting for o2,sleeping......
//flag = 2
//lock o2,waitting for o1,sleeping......
}
}
