读写锁:核心思想实现读写分离,高并发下特别适合 读多写少的场景。
synchronized关键字和ReentrantLock 同一时间只能有一个线程进行访问被锁定的代码,读写锁的机制则不是,本质上分为两把锁,读锁和写锁,在读锁情况下,多个线程可以并发访问资源,只有当是写锁时只能一个一个的顺序执行。
口诀:读读共享,写写互斥,读写互斥。
private ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();
private ReentrantReadWriteLock.ReadLock readLock = rwLock.readLock();
private ReentrantReadWriteLock.WriteLock writeLock = rwLock.writeLock();
public void read() {
try {
readLock.lock();
System.out.println("当前线程:" + Thread.currentThread().getName() + "进入...");
Thread.sleep(3000);
System.out.println("当前线程:" + Thread.currentThread().getName() + "退出...");
} catch (Exception e) {
e.printStackTrace();
} finally {
readLock.unlock();
}
}
public void write() {
try {
writeLock.lock();
System.out.println("当前线程:" + Thread.currentThread().getName() + "进入...");
Thread.sleep(3000);
System.out.println("当前线程:" + Thread.currentThread().getName() + "退出...");
} catch (Exception e) {
e.printStackTrace();
} finally {
writeLock.unlock();
}
}