两个线程1-100轮流打印
第一种方法： synchronized关键字
static int num=0;
public static void main(String[] args) {
Object o = new Object(); //要锁住的资源类
Runnable runnable =
new Runnable() {
@Override
public void run() {
while (num < 100) {
synchronized (o) {
o.notify();
num++;
System.out.println(Thread.currentThread().getName() + ":" + num);
try {
//避免b线程最后不能被唤醒一直等待导致线程不结束
if(num<100){
o.wait();
}else {
o.notify();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
System.out.println(Thread.currentThread().getName()+"结束");
}
};
new Thread(runnable,"a").start();
new Thread(runnable,"b").start();
}
第二种方法： ReentrantLock 的 Condition
public class ShareCahe {
private int num = 0;
private static boolean flag = true;
private static Lock lock = new ReentrantLock();
private static Condition condition1 = lock.newCondition();
private static Condition condition2 = lock.newCondition();
public int getNum() {
return num;
}
public void condition1AddOne(){
lock.lock();
try{
while(!flag){
condition1.await();
}
if(num<100){
num++;
System.out.println(Thread.currentThread().getName()+":"+num);
}
flag = false;
condition2.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally{
lock.unlock();
}
}
public void condition2AddOne(){
lock.lock();
try{
while(flag){
condition2.await();
}
if(num<100){
num++;
System.out.println(Thread.currentThread().getName()+":"+num);
}
flag=true;
condition1.signal();
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
lock.unlock();
}
}
public static void main(String[] args) throws InterruptedException {
ShareCahe shareCahe = new ShareCahe();
new Thread(()->{
while(shareCahe.getNum()<100){
shareCahe.condition1AddOne();
}
},"a").start();
new Thread(
() -> {
while (shareCahe.getNum()<100) {
shareCahe.condition2AddOne();
}
},
"b")
.start();
Thread.sleep(200);
System.out.println("====="+shareCahe.getNum());
}
}
利用condition的话是可以完成多个线程轮流打印的，不只是两个线程，这里的思想就在于，我利用了一个flag 来表示标志位，当flag为true时，线程a开始执行执行完后把flag置为false，否则调用await(),让出锁资源，并让自己处于等待状态。b线程也是同理，只是b线程是flag为false才执行，通过两个线程的自己等待，对方唤醒来达到相互执行的效果
