SLEEP
sleep 意思是睡眠,当前线程暂停一段时间让给别的线程去运行。sleep是怎么复活的?由你的睡眠时间而定,等睡眠到规定的时间自动复活,CPU 没有线程的概念,会不断的从内存中获取指令去执行,睡眠的意思就是当前线程让出cpu 由其他线程去执行。
static void testSleep() {
new Thread(()->{
for(int i=0; i<100; i++) {
System.out.println("A" + i);
try {
Thread.sleep(500);
//TimeUnit.Milliseconds.sleep(500)
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
}
public static void main(String[] args) throws InterruptedException {
sleep();
// yield();
// join();
}
YIELD
yield 让出当前cpu进入线程的等待队列,下一次能不能进入线程看自己能不能抢到,当yield让出cpu后后续更大可能是将等待队列里面的线程拿过来进行执行。暂时没有应用场景。
static void yield(){
new Thread(()->{
for (int i = 0; i < 100; i++) {
try {
if (i % 10 == 0) {
Thread.yield();
}
System.out.println("i am thread a");
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(()->{
for (int i = 0; i < 100; i++) {
try {
if (i % 10 == 0) {
Thread.yield();
}
System.out.println("i am thread b");
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
}
public static void main(String[] args) throws InterruptedException {
// sleep();
yield();
//join();
}
JOIN
在当前线程加入你调用join的线程,此处是t1 线程加入到t2线程里面去了,当t2线程执行到 join的时候,就会去执行t1线程,只有t1 线程执行完成之后才会接着执行t2线程。
static void join() throws InterruptedException {
Thread t1 = new Thread(() -> {
for (int i = 0; i < 100; i++) {
try {
System.out.println("i am thread a");
TimeUnit.SECONDS.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
Thread t2 = new Thread(() -> {
for (int i = 0; i < 100; i++) {
try {
System.out.println("i am thread b");
t1.join();
System.out.println("i am thread b");
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
t1.start();
TimeUnit.SECONDS.sleep(10);
t2.start();
}
public static void main(String[] args) throws InterruptedException {
// sleep();
// yield();
join();
}