这个例子解释lock, Condition, while()控制的使用
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class LockCoditionText {
final Business business = new Business();
public static void main(String[] args) {
new LockCoditionText().init();
}
private void init() {
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i <= 50; i++) {
business.sub(i);//(1)调用sub方法并将bShuldSub置为false
}
}
}).start();
for (int i = 0; i <= 50; i++) {
business.main(i);
}
}
class Business {
private boolean bShouldSub = true;
Lock lock = new ReentrantLock();
Condition condition = lock.newCondition();
public void sub(int i) {
//加锁,此线程不能被其他线程打断
lock.lock();
try {
//如果bShowldSub为false, 进入等待
while (!bShouldSub) {
condition.await();
}
for (int j = 1; j <= 10; j++) {
System.out.println("sub thread sequence of" + j
+ ",loop of " + i);
}
//以后main方法中可以执行
bShouldSub = false;
condition.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
//解锁,此线程结束
lock.unlock();
}
}
public synchronized void main(int i) {
//加锁
lock.lock();
try {
while (bShouldSub) {
condition.await();
}
for (int j = 1; j <= 10; j++) {
System.out.println("main thread sequence of" + j
+ ",loop of " + i);
}
//使sub方法可以执行
bShouldSub = true;
condition.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
//解锁
lock.unlock();
}
}
}
}
API文档上例子如下：
class BoundedBuffer {
final Lock lock = new ReentrantLock();
//下面使用两个condition可以使用put控制take的执行
final Condition notFull = lock.newCondition();
final Condition notEmpty = lock.newCondition();
final Object[] items = new Object[100];
int putptr, takeptr, count;
public void put(Object x) throws InterruptedException {
lock.lock();
try {
while (count == items.length)
notFull.await();
items[putptr] = x;
if (++putptr == items.length) putptr = 0;
++count;
notEmpty.signal();
} finally {
lock.unlock();
}
}
public Object take() throws InterruptedException {
lock.lock();
try {
while (count == 0)
notEmpty.await();
Object x = items[takeptr];
if (++takeptr == items.length) takeptr = 0;
--count;
notFull.signal();
return x;
} finally {
lock.unlock();
}
}
ArrayBlockingQueue类提供了这项功能
三个条件多路通信 老大通知老二，老二通知老三，老三通知老大
package cn.edu.zzuli;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class LockCoditionText {
final Business business = new Business();
public static void main(String[] args) {
new LockCoditionText().init();
}
private void init() {
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i <= 50; i++) {
business.sub2(i);
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i <= 50; i++) {
business.sub3(i);
}
}
}).start();
for (int i = 0; i <= 50; i++) {
business.main(i);
}
}
class Business {
private int flag = 1;
Lock lock = new ReentrantLock();
Condition condition1 = lock.newCondition();
Condition condition2= lock.newCondition();
Condition condition3= lock.newCondition();
public void sub2(int i) {
lock.lock();
try {
while (flag!=2) {
condition2.await();
}
for (int j = 1; j <= 10; j++) {
System.out.println("sub2 thread sequence of" + j
+ ",loop of " + i);
}
flag = 3;
condition3.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void sub3(int i) {
lock.lock();
try {
while (flag!=3) {
condition3.await();
}
for (int j = 1; j <= 10; j++) {
System.out.println("sub3 thread sequence of" + j
+ ",loop of " + i);
}
flag =1;
condition1.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public synchronized void main(int i) {
lock.lock();
try {
while (flag!=1) {
condition1.await();
}
for (int j = 1; j <= 20; j++) {
System.out.println("main thread sequence of" + j
+ ",loop of " + i);
}
flag = 2;
condition2.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
}