ReentrantReadWriteLock的相关使用
2024-10-07 16:24:03
ReentrantLock具有完全互斥排他的效果，同一时间只有一个线程执行ReentrantLock.lock()方法后面的任务，这样虽然能够保证线程安全性，但是效率是比较低的
ReentrantReadWriteLock可以加快运行效率
ReentrantReadWriteLock读写锁有两个锁，读锁和写锁，读锁是共享锁，写锁是排他锁：
- 读锁与读锁不互斥
- 写锁与写锁互斥
- 读锁与写锁互斥
- 写锁与读锁互斥
ReentrantReadWriteLock
读锁与读锁不互斥
public class Test01 {
private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public void read(){
try {
lock.readLock().lock();
System.out.println("获取读锁"+Thread.currentThread().getName()+" "+System.currentTimeMillis());
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.readLock().unlock();
}
}
public static void main(String[] args) {
Test01 test = new Test01();
Runnable runnable = new Runnable() {
@Override
public void run() {
test.read();
}
};
Thread a = new Thread(runnable);
a.setName("A");
Thread b = new Thread(runnable);
b.setName("B");
a.start();
b.start();
}
}
-------------------------------------------------console-------------------------------------------------
获取读锁A 1539155032025
获取读锁B 1539155032025
打印结果显示线程A，B同时读取锁，证明多个线程获得读锁是不互斥的，使用读锁可以提高程序运行效率
写锁与写锁互斥
public class Test02 {
private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public void write(){
try {
lock.writeLock().lock();
System.out.println("获取写锁"+Thread.currentThread().getName()+" "+System.currentTimeMillis());
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.writeLock().unlock();
}
}
public static void main(String[] args) {
Test02 test = new Test02();
Runnable runnable = new Runnable() {
@Override
public void run() {
test.write();
}
};
Thread a = new Thread(runnable);
a.setName("A");
Thread b = new Thread(runnable);
b.setName("B");
a.start();
b.start();
}
}
-------------------------------------------------console-------------------------------------------------
获取写锁A 1539155285755
获取写锁B 1539155295757
证明同一时间只允许一个线程执行lock()方法后面的代码
读锁与写锁互斥，写锁与读锁互斥
public class Test03 {
private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public void read(){
try {
lock.readLock().lock();
System.out.println("获取读锁"+Thread.currentThread().getName()+" "+System.currentTimeMillis());
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.readLock().unlock();
}
}
public void write(){
try {
lock.writeLock().lock();
System.out.println("获取写锁"+Thread.currentThread().getName()+" "+System.currentTimeMillis());
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.writeLock().unlock();
}
}
public static void main(String[] args) {
Test03 test = new Test03();
Thread a = new Thread(new Runnable() {
@Override
public void run() {
test.read();
}
});
a.setName("A");
Thread b = new Thread(new Runnable() {
@Override
public void run() {
test.write();
}
});
b.setName("B");
a.start();
b.start();
}
}
-------------------------------------------------console-------------------------------------------------
获取读锁A 1539155559525
获取写锁B 1539155569525
证明读写操作是互斥的，只要出现写操作的过程就是互斥的
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