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WaitFirstThread.java
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122 lines (117 loc) · 3.57 KB
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/**
* 模拟Redis查询操作
*/
class Status {
private volatile int status;
/**
* 模拟Redis查询操作
*
* @return 查询结果
*/
public int getStatus() {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return status;
}
public void setStatus(int status) {
/**
* 模拟Redis查询并设置key操作，可能比较耗时，所有加了sleep
*/
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
this.status = status;
}
}
public class WaitFirstThread {
/**
* 第一个版本，读线程会阻塞（串行执行）
*/
public void waitOne() {
final Status status = new Status();
ReentrantLock lock = new ReentrantLock();
Runnable r = () -> {
if (status.getStatus() == 0) {
lock.lock();
try {
if (status.getStatus() == 0) {
System.out.println("查询");
status.setStatus(1);
} else {
System.out.println("直接返回1:" + status.getStatus());
}
} finally {
lock.unlock();
}
} else {
System.out.println("直接返回2:" + status.getStatus());
}
};
ExecutorService executorService = Executors.newFixedThreadPool(100);
for (int i = 0; i < 10; i++) {
executorService.submit(r);
}
executorService.shutdown();
}
/**
* 第二个版本，用while循环等待，支持读并发
*/
public void waitTwo() {
final Status status = new Status();
ReentrantLock lock = new ReentrantLock();
AtomicInteger counter = new AtomicInteger(0);
Runnable r = () -> {
counter.getAndIncrement();
if (counter.get() > 1) {
while (status.getStatus() == 0) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("直接返回:" + status.getStatus());
} else {
status.setStatus(1);
System.out.println("查询");
}
};
ExecutorService executorService = Executors.newFixedThreadPool(100);
for (int i = 0; i < 10; i++) {
executorService.submit(r);
}
executorService.shutdown();
}
/**
* 第三个版本，信号量控制
*/
public void waitThree() {
final Status status = new Status();
Semaphore s = new Semaphore(1);
Runnable r = () -> {
try {
s.acquire(1);
if (status.getStatus() == 0){
status.setStatus(1);
System.out.println("查询");
}
if (s.availablePermits() < 1){
s.release(10);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("直接返回:" + status.getStatus());
};
ExecutorService executorService = Executors.newFixedThreadPool(100);
for (int i = 0; i < 100; i++) {
executorService.submit(r);
}
executorService.shutdown();
}
}