public class CyclicBar {
private final static CyclicBarrier cb = new CyclicBarrier(3,
new Runnable() {
@Override
public void run() {
System.out.println("\n-------------");
}
});
public static void main(String[] args) {
final class ColouredRunnable implements Runnable {
private int i;
public ColouredRunnable(int j) {
this.i = j;
}
@Override
public void run() {
final String name = Thread.currentThread().getName();
while (true) {
cyclicAwait();
for (int i = 0; i < name.length(); i++) {
sleep();
// System.out.print("" + name.charAt(i) + this.i + " ");
System.out.print("" + name.charAt(i) + " ");
}
}
}
}
;
int i = 0;
new Thread(new ColouredRunnable(i++), "RED").start();
new Thread(new ColouredRunnable(i++), "BLUE").start();
new Thread(new ColouredRunnable(i++), "GREEN").start();
}
private static int cyclicAwait() {
try {
return cb.await();
} catch (InterruptedException | BrokenBarrierException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return -1;
}
private static void sleep() {
try {
Thread.sleep(ThreadLocalRandom.current().nextLong(200, 600));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
以上代码目前正在打印
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G R B R E L E E D U E N
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B R G E R L U E D E E N
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R G B E L R E U D E E N
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R G B E R L U E D E E N
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B R G E L D R U E E E N
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如何更改上述代码并在适当的位置添加适当的屏障以产生以下输出
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R E D B L U E G R E E N
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R E D B L U E G R E E N
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R E D B L U E G R E E N
约束
synchronised wait notify 答案 0 :(得分：1)
public class TestSynMain {
private final static AbstractQueuedSynchronizer cb = new TestSynchronizer(6);
public static void main(String[] args) {
final class ColouredRunnable implements Runnable {
private String color;
public ColouredRunnable(String color) {
this.color = color;
}
@Override
public void run() {
while (true) {
try {
boolean result = false;
do{
result = cb.tryAcquireNanos(Integer.parseInt(Thread.currentThread().getName()), TimeUnit.MILLISECONDS.toNanos(1000));
}while(!result);
for (int i = 0; i < color.length(); i++) {
try {
Thread.sleep(300);
} catch (InterruptedException e) {
System.exit(-1);
}
System.out.print("" + color.charAt(i) + " ");
}
} catch (NumberFormatException e1) {
e1.printStackTrace();
} catch (InterruptedException e1) {
e1.printStackTrace();
}finally{
cb.release(Integer.parseInt(Thread.currentThread().getName()));
}
}
}
}
new Thread(new ColouredRunnable("RED"), "0").start();
new Thread(new ColouredRunnable("BLUE"), "1").start();
new Thread(new ColouredRunnable("GREEN"), "2").start();
new Thread(new ColouredRunnable("BLACK"), "3").start();
new Thread(new ColouredRunnable("MAGENTA"), "4").start();
new Thread(new ColouredRunnable("WHITE"), "5").start();
}
}
public class TestSynchronizer extends AbstractQueuedSynchronizer{
/**
*
*/
private static final long serialVersionUID = 1L;
int count;
public TestSynchronizer(int count) {
this.count = count;
setState(0);
}
@Override
protected boolean tryAcquire(int arg) {
if(arg == getState()){
System.out.println("Acquires" + Thread.currentThread().getName());
setExclusiveOwnerThread(Thread.currentThread());
return true;
}
return false;
}
@Override
protected boolean tryRelease(int arg) {
int state = getState();
setState(++state % count);
setExclusiveOwnerThread(null);
return true;
}
}
Synchronizer接受一个参数count，该参数最多可以同步多少个线程。
线程的名称必须是他们需要采取的订单。现在，您可以根据需要添加任意数量的线程。
我设计了一个自定义Synchronizer并用它来定义一个允许锁定和解锁线程的新策略。
答案 1 :(得分：1)
如果你想玩它们，Phasers也很酷。所有这一点要求你用你想要的任何单词填充words列表 - 它为每个单词创建一个主题并且它们都可以很好地运行。
public class PhaserTest
{
private final Phaser phaser = new Phaser(1) {
protected boolean onAdvance(int phase, int parties)
{
//Phaser version of your CyclicBarrier Runnable
if(parties == 1)
System.out.println("\n-------------");
return false;
}
};
public void runTest()
{
List<String> words = Arrays.asList("RED", "BLUE", "GREEN");
for(int i = 0; i < words.size();i++)
new Thread(new ColouredRunnable(words.get(i),i + 1)).start();
while(phaser.arriveAndAwaitAdvance() != (words.size() + 1)){}
System.out.println("Done.");
}
public class ColouredRunnable implements Runnable {
private final int order;
private final String color;
public ColouredRunnable(String s, int order) {
this.color = s;
this.order = order;
phaser.register();
}
@Override
public void run() {
while(phaser.arriveAndAwaitAdvance() != order){}
for (int i = 0; i < color.length(); i++) {
sleep();
System.out.print("" + color.charAt(i) + " ");
}
phaser.arriveAndDeregister();
}
private void sleep() {
try {
Thread.sleep(ThreadLocalRandom.current().nextLong(200, 600));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
答案 2 :(得分：0)
此解决方案使用3个循环障碍。代码最初使用循环障碍在线程之间创建托管死锁。触发cb[cb.length-1].await();线程中的main
public static void main(String[] args) {
String colors[] = { "RED", "BLUE", "GREEN" };
final CyclicBarrier[] cb = createCB(colors);
for (int i = 0; i < colors.length; i++) {
final int j = i;
new Thread(colors[i]) {
public void run() {
while (true) {
try {
cb[(j == 0 ? cb.length : j) - 1].await();// Wait for
// previous
// barrier
String name = getName();
for (int i = 0; i < name.length(); i++) {
CyclicBari.sleep();
System.out.print(" " + name.charAt(i) + " ");
}
cb[j].await();// Notify next
} catch (InterruptedException | BrokenBarrierException e) {
e.printStackTrace();
}
}
}
}.start();
}
System.out.println("start");
try {
cb[cb.length-1].await();
} catch (InterruptedException | BrokenBarrierException e) {
e.printStackTrace();
}
}
private static void sleep() {
try {
Thread.sleep(ThreadLocalRandom.current().nextLong(200, 600));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private static CyclicBarrier[] createCB(String[] colors) {
final CyclicBarrier cb[] = new CyclicBarrier[colors.length];
for (int i = 0; i < cb.length; i++) {
final int j = i;
cb[i] = new CyclicBarrier(2, new Runnable() {
@Override
public void run() {
if (j == cb.length - 1) {
System.out.println("\n-------------");
} else {
System.out.print(".");
}
}
});
}
return cb;
}
输出
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R E D . B L U E . G R E E N
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R E D . B L U E . G R E E N
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R E D . B L U E . G R E E N
-------------