Java并发编程核心方法与框架-phaser的使用
arriveAndAwaitAdvance()方法
arriveAndAwaitAdvance()作用是当前线程已经到达屏障，在此等待一段时间，等条件满足后继续向下一个屏障执行。
public class PrintTools {
public static Phaser phaser;
public static void methodA() {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
System.out.println(Thread.currentThread().getName() + " A2 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A2 end " + System.currentTimeMillis());
}
public static void methodB() {
try {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
Thread.sleep(5000);
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
System.out.println(Thread.currentThread().getName() + " A2 begin " + System.currentTimeMillis());
Thread.sleep(5000);
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A2 end " + System.currentTimeMillis());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public class ThreadA extends Thread {
@Override
public void run() {
PrintTools.methodA();//执行A方法
}
}
public class ThreadB extends Thread {
@Override
public void run() {
PrintTools.methodA();//执行A方法
}
}
public class ThreadC extends Thread {
@Override
public void run() {
PrintTools.methodB();//执行B方法
}
}
public class Main {
public static void main(String[] args) {
Phaser phaser = new Phaser(3);
PrintTools.phaser = phaser;
ThreadA a = new ThreadA();
a.setName("A");
a.start();
ThreadB b = new ThreadB();
b.setName("B");
b.start();
ThreadC c = new ThreadC();
c.setName("C");
c.start();
}
}
程序运行结果如下：
A A1 begin 1469711023742
B A1 begin 1469711023742
C A1 begin 1469711023743
C A1 end 1469711028745
A A1 end 1469711028745
B A1 end 1469711028745
A A2 begin 1469711028745
C A2 begin 1469711028745
B A2 begin 1469711028745
B A2 end 1469711033748
C A2 end 1469711033748
A A2 end 1469711033748
A、B线程会等待C线程一起到达屏障点，然后一起继续向下执行。
对以上代码做如下修改：
public class PrintTools {
public static Phaser phaser;
public static void methodA() {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
System.out.println(Thread.currentThread().getName() + " A2 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A2 end " + System.currentTimeMillis());
}
public static void methodB() {
try {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
Thread.sleep(5000);
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
/* C提前退出比赛
System.out.println(Thread.currentThread().getName() + " A2 begin " + System.currentTimeMillis());
Thread.sleep(5000);
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A2 end " + System.currentTimeMillis());
*/
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//其他代码保持不变
重新运行程序，控制台打印结果如下：
A A1 begin 1469711274416
B A1 begin 1469711274416
C A1 begin 1469711274417
B A1 end 1469711279421
C A1 end 1469711279421
A A1 end 1469711279421
B A2 begin 1469711279421
A A2 begin 1469711279421
A、B到达第二个屏障点后等不到C的到来，程序不结束，将会一直等下去。
arriveAndDeregister()方法
arriveAndDeregister()方法的作用是使线程退出比赛，并且使parties值减1
对以上代码做如下修改：
public class PrintTools {
public static Phaser phaser;
public static void methodA() {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
System.out.println(Thread.currentThread().getName() + " A2 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A2 end " + System.currentTimeMillis());
}
public static void methodB() {
try {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
Thread.sleep(5000);
System.out.println("A:" + phaser.getRegisteredParties());
phaser.arriveAndDeregister();//退出比赛
System.out.println("B:" + phaser.getRegisteredParties());
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//其他代码保持不变
程序运行结果如下：
A A1 begin 1469711921794
B A1 begin 1469711921795
C A1 begin 1469711921795
A:3
B:2
B A1 end 1469711926799
C A1 end 1469711926799
A A1 end 1469711926799
B A2 begin 1469711926799
A A2 begin 1469711926800
B A2 end 1469711926800
A A2 end 1469711926800
此时程序可以正常结束。
onAdvance()方法
public class MyService {
private Phaser phaser;
public MyService(Phaser phaser) {
super();
this.phaser = phaser;
}
public void testMethod() {
try {
System.out.println("阶段1 Begin " + Thread.currentThread().getName() + System.currentTimeMillis());
if (Thread.currentThread().getName().equals("B")) {
Thread.sleep(5000);
}
phaser.arriveAndAwaitAdvance();
System.out.println("阶段1 End " + Thread.currentThread().getName() + " end phase value=" + phaser.getPhase() + " " + System.currentTimeMillis());
/********/
System.out.println("阶段2 Begin " + Thread.currentThread().getName() + System.currentTimeMillis());
if (Thread.currentThread().getName().equals("B")) {
Thread.sleep(5000);
}
phaser.arriveAndAwaitAdvance();
System.out.println("阶段2 End " + Thread.currentThread().getName() + " end phase value=" + phaser.getPhase() + " " + System.currentTimeMillis());
/********/
System.out.println("阶段3 Begin " + Thread.currentThread().getName() + System.currentTimeMillis());
if (Thread.currentThread().getName().equals("B")) {
Thread.sleep(5000);
}
phaser.arriveAndAwaitAdvance();
System.out.println("阶段3 End " + Thread.currentThread().getName() + " end phase value=" + phaser.getPhase() + " " + System.currentTimeMillis());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//省略ThreadA、ThreadB
public class Main {
public static void main(String[] args) {
Phaser phaser = new Phaser(2){
@Override
protected boolean onAdvance(int phase, int registeredParties) {
System.out.println("onAdvance 被" + Thread.currentThread().getName() + "调用 " + System.currentTimeMillis() + " phase value=" + phase + " registeredParties=" + registeredParties);
return false;
//返回true 不等待，Phaser呈无效/销毁的状态
//返回false则Phaser继续工作
}
};
MyService service = new MyService(phaser);
ThreadA a = new ThreadA(service);
a.setName("A");
a.start();
ThreadB b = new ThreadB(service);
b.setName("B");
b.start();
}
}
运行程序，控制台打印结果如下：
阶段1 Begin A1470103011668
阶段1 Begin B1470103011669
onAdvance 被B调用 1470103016670 phase value=0 registeredParties=2
阶段1 End B end phase value=1 1470103016670
阶段1 End A end phase value=1 1470103016670
阶段2 Begin A1470103016670
阶段2 Begin B1470103016670
onAdvance 被B调用 1470103021675 phase value=1 registeredParties=2
阶段2 End B end phase value=2 1470103021675
阶段2 End A end phase value=2 1470103021675
阶段3 Begin A1470103021675
阶段3 Begin B1470103021675
onAdvance 被B调用 1470103026677 phase value=2 registeredParties=2
阶段3 End B end phase value=3 1470103026677
阶段3 End A end phase value=3 1470103026677
onAdvance()在B线程到达屏障点时被调用。如果在onAdvance()方法中返回true，Phaser会被销毁。
对main函数中的代码做如下修改：
public class Main {
public static void main(String[] args) {
Phaser phaser = new Phaser(2){
@Override
protected boolean onAdvance(int phase, int registeredParties) {
System.out.println("onAdvance 被" + Thread.currentThread().getName() + "调用 " + System.currentTimeMillis() + " phase value=" + phase + " registeredParties=" + registeredParties);
return true;
//返回true 不等待，Phaser呈无效/销毁的状态
//返回false则Phaser继续工作
}
};
MyService service = new MyService(phaser);
ThreadA a = new ThreadA(service);
a.setName("A");
a.start();
ThreadB b = new ThreadB(service);
b.setName("B");
b.start();
}
}
重新运行程序，控制台打印结果如下：
阶段1 Begin A1470103416899
阶段1 Begin B1470103416899
onAdvance 被B调用 1470103421901 phase value=0 registeredParties=2
阶段1 End B end phase value=-2147483647 1470103421901
阶段1 End A end phase value=-2147483647 1470103421901
阶段2 Begin B1470103421901
阶段2 Begin A1470103421901
阶段2 End A end phase value=-2147483647 1470103421901
阶段3 Begin A1470103421901
阶段3 End A end phase value=-2147483647 1470103421902
阶段2 End B end phase value=-2147483647 1470103426905
阶段3 Begin B1470103426905
阶段3 End B end phase value=-2147483647 1470103431907
arrive()方法
arrive()方法的作用是使parties值加1，并且不在屏障处等待，直接向下面的代码继续运行，并且充值Phaser类的计数。
public class Run {
public static void main(String[] args) {
Phaser phaser = new Phaser(2){
@Override
protected boolean onAdvance(int phase, int registeredParties) {
System.out.println("到达了未通过！phase=" + phase + " registeredParties=" + registeredParties);
return super.onAdvance(phase, registeredParties);
}
};
System.out.println("A1，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
phaser.arrive();
System.out.println("A1，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
System.out.println("A2，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
phaser.arrive();
System.out.println("A2，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
//---------
System.out.println("B1，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
phaser.arrive();
System.out.println("B1，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
System.out.println("B2，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
phaser.arrive();
System.out.println("B2，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
//---------
System.out.println("C1，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
phaser.arrive();
System.out.println("C1，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
System.out.println("C2，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
phaser.arrive();
System.out.println("C2，getPhase=" + phaser.getPhase() + " getRegisteredParties=" + phaser.getRegisteredParties() + " getArrivedParties=" + phaser.getArrivedParties());
}
}
运行程序，控制台打印结果如下：
A1，getPhase=0 getRegisteredParties=2 getArrivedParties=0
A1，getPhase=0 getRegisteredParties=2 getArrivedParties=1
A2，getPhase=0 getRegisteredParties=2 getArrivedParties=1
到达了未通过！phase=0 registeredParties=2
A2，getPhase=1 getRegisteredParties=2 getArrivedParties=0
B1，getPhase=1 getRegisteredParties=2 getArrivedParties=0
B1，getPhase=1 getRegisteredParties=2 getArrivedParties=1
B2，getPhase=1 getRegisteredParties=2 getArrivedParties=1
到达了未通过！phase=1 registeredParties=2
B2，getPhase=2 getRegisteredParties=2 getArrivedParties=0
C1，getPhase=2 getRegisteredParties=2 getArrivedParties=0
C1，getPhase=2 getRegisteredParties=2 getArrivedParties=1
C2，getPhase=2 getRegisteredParties=2 getArrivedParties=1
到达了未通过！phase=2 registeredParties=2
C2，getPhase=3 getRegisteredParties=2 getArrivedParties=0
方法arrive()的功能是使getArrivedParties()计数加1，不等待其他线程到达屏障。控制台多次出现getArrivedParties=0说明Phaser类经过屏障点后计数被重置。
arriveAdvance(int phase)方法的作用是：如果传入参数phase值和当前getPhase()方法返回值一样，则在屏障处等待，否则继续向下面运行。
public class ThreadA extends Thread {
private Phaser phaser;
public ThreadA(Phaser phaser) {
super();
this.phaser = phaser;
}
@Override
public void run() {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
}
}
public class ThreadB extends Thread {
private Phaser phaser;
public ThreadB(Phaser phaser) {
super();
this.phaser = phaser;
}
@Override
public void run() {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
}
}
public class ThreadC extends Thread {
private Phaser phaser;
public ThreadC(Phaser phaser) {
super();
this.phaser = phaser;
}
@Override
public void run() {
try {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
Thread.sleep(3000);
phaser.awaitAdvance(0);//跨栏的栏数。不参与parties计数的操作，仅具有判断功能。
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public class ThreadD extends Thread {
private Phaser phaser;
public ThreadD(Phaser phaser) {
super();
this.phaser = phaser;
}
@Override
public void run() {
try {
System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());
Thread.sleep(5000);
phaser.arriveAndAwaitAdvance();
System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public class Main {
public static void main(String[] args) {
Phaser phaser = new Phaser(3);
ThreadA a = new ThreadA(phaser);
a.setName("A");
a.start();
ThreadB b = new ThreadB(phaser);
b.setName("B");
b.start();
ThreadC c = new ThreadC(phaser);
c.setName("C");
c.start();
ThreadD d = new ThreadD(phaser);
d.setName("D");
d.start();
}
}
程序运行结果如下：
A A1 begin 1470226617412
B A1 begin 1470226617412
C A1 begin 1470226617413
D A1 begin 1470226617414
C A1 end 1470226622416
B A1 end 1470226622416
A A1 end 1470226622416
D A1 end 1470226622416
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