java-多线程-join函数

join()>>不带参数

线程A调用线程B.join,意思就是线程A并入了线程B,当执行完线程B,再去执行线程A后续动作

join(int keepTims)>>带参数,与上面类似,区别在于线程B保持并入线程A中有保持时间,超过改时间,两线程再次分开

案例1

package com.wp.join;

public class JoinTest implements Runnable {

public static int a = 0;

@Override
public void run() {
for(;;){
a++;
System.out.println("变量A="+a);
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 1000) {
}
if(a>8){
break;
}
}
}

public static void main(String[] args) {
Thread task = new Thread(new JoinTest());
task.start();
try {
task.join(9000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("End var = "+a);
}

}

案例2

package com.wp.join;

public class JoinTest2 {

private static int num = 0;

static class JoinThreadA extends Thread {

@Override
public void run() {
while (true) {
num++;
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 200) {
}
System.out.println("选手A已跑" + num + "米");
if (num >= 100) {
break;
}
}
}
}

static class JoinThreadB extends Thread {
protected JoinThreadA joina;

public JoinThreadB(JoinThreadA joina) {
this.joina = joina;
}

@Override
public void run() {
try {
joina.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
while (true) {
num++;
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 100) {
}
System.out.println("选手B已跑" + num + "米");
if (num >= 200) {
break;
}
}

}
}
static class JoinThreadC extends Thread {
protected JoinThreadB joinb;

public JoinThreadC(JoinThreadB joinb) {
this.joinb = joinb;
}

@Override
public void run() {
try {
joinb.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
while (true) {
num++;
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 50) {
}
System.out.println("选手C已跑" + num + "米");
if (num >= 300) {
break;
}
}

}
}

static class JoinThreadD extends Thread {
protected JoinThreadC joinc;

public JoinThreadD(JoinThreadC joinc) {
this.joinc = joinc;
}

@Override
public void run() {
try {
joinc.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
while (true) {
num++;
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 20) {
}
System.out.println("选手D已跑" + num + "米");
if (num >= 400) {
break;
}
}

}
}

public static void main(String[] args) throws Exception {
System.out.println("比赛开始");
JoinThreadA joina = new JoinThreadA();
JoinThreadB joinb = new JoinThreadB(joina);
JoinThreadC joinc = new JoinThreadC(joinb);
JoinThreadD joind = new JoinThreadD(joinc);
joina.start();
joinb.start();
joinc.start();
joind.start();
joind.join();
System.out.println("比赛结束,最终跑完" + num + "米");
}

}

案例三

package com.wp.join;

import java.text.SimpleDateFormat;
import java.util.Date;

public class JoinTest3 {
final static SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

static class JoinThread extends Thread {
Thread syncThread;

public JoinThread(Thread syncThread) {
this.syncThread = syncThread;
}

@Override
public void run() {
synchronized (syncThread) {
System.out.println("线程A START");
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 5000) {
}
System.out.println("线程A END");
}
}
}

public static void main(String[] args) {
System.out.println("开始时间:"+format.format(new Date()));
Thread t1 = new Thread(new Runnable() {

@Override
public void run() {
System.out.println("Begin sleep");
long now = System.currentTimeMillis();
while (System.currentTimeMillis() - now < 5000) {
}
System.out.println("End sleep");

}
});
Thread t2 = new JoinThread(t1);
t1.start();
t2.start();
try {
t1.join(1000);//因为T1线程对象的锁被T2持有,所以必须等T2跑完,释放锁 所以此处等待的时间 1000+5000
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("结束时间:"+format.format(new Date()));
}

}