下面的文章内容要给大家介绍的就是ReadWriteLock，一起来了解一下ReadWriteLock的使用方法以及它的适用场景吧。
ReadWriteLock使用方法：
/**
* 多个线程同时读一个资源类没有任何问题，所以为了满足并发量，读取共享资源
* 应该同时进行。
* 但是，如果有一个线程想去写共享资源来，就不应该再有其它线程可以对该资源进行读或者写
* 小结：
* 读—读能共存
* 读写不能共存
* 写写不能共存
*/
public static void main(String[] args)
{
Mycache mycache = new Mycache();
for (int i = 0; i <= 5; i++)
{
final int t = i;
new Thread(() - >
{
mycache.put(Thread.currentThread()
.getName(), t + "");
}, String.valueOf(i))
.start();
}
for (int i = 0; i <= 5; i++)
{
new Thread(() - >
{
mycache.get(Thread.currentThread()
.getName());
}, String.valueOf(i))
.start();
}
}
}
class Mycache
{
private volatile HashMap < String, Object > hashMap = new HashMap < > ();
private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
public void put(String key, Object value)
{
readWriteLock.writeLock()
.lock();
try
{
System.out.println(Thread.currentThread()
.getName() + "\t写入数据" + key);
hashMap.put(key, value);
System.out.println(Thread.currentThread()
.getName() + "\t写入完成");
}
catch (Exception e)
{}
finally
{
readWriteLock.writeLock()
.unlock();
}
}
public void get(String key)
{
readWriteLock.readLock()
.lock();
try
{
System.out.println(Thread.currentThread()
.getName() + "\t读取数据" + key);
hashMap.get(key);
System.out.println(Thread.currentThread()
.getName() + "\t读取完成");
}
catch (Exception e)
{}
finally
{
readWriteLock.readLock()
.unlock();
}
}ReadWriteLock使用案例
举个例子来应用读写锁，ReentrantReadWriteLock是ReadWriteLock的实现类。
最主要的有2个方法：readLock()和writeLock()用来获取读锁和写锁。
代码：
public class ReadWriteLockDemo
{
private static final ReentrantReadWriteLock reentrantReadWriteLock = new ReentrantReadWriteLock();
private static ReentrantReadWriteLock.ReadLock readLock = reentrantReadWriteLock.readLock();
private static ReentrantReadWriteLock.WriteLock writeLock = reentrantReadWriteLock.writeLock();
public static void main(String[] args)
{
new Thread(() - > read())
.start();
new Thread(() - > read())
.start();
new Thread(() - > write())
.start();
new Thread(() - > write())
.start();
}
private static void read()
{
String threadName = Thread.currentThread()
.getName();
readLock.lock();
try
{
System.out.println(threadName + "-获取读锁(readLock)，读取数据...");
Thread.sleep(1000);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
finally
{
System.out.println(threadName + "-释放读锁(readLock)");
readLock.unlock();
}
}
private static void write()
{
String threadName = Thread.currentThread()
.getName();
writeLock.lock();
try
{
System.out.println(threadName + "-获取写锁(writeLock)，写入数据...");
Thread.sleep(1000);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
finally
{
System.out.println(threadName + "-释放读锁(writeLock)");
writeLock.unlock();
}
}
}结果：
Thread - 0 - 获取读锁(readLock)， 读取数据... Thread - 1 - 获取读锁(readLock)， 读取数据... Thread - 0 - 释放读锁(readLock) Thread - 1 - 释放读锁(readLock) Thread - 2 - 获取写锁(writeLock)， 写入数据... Thread - 2 - 释放写锁(writeLock) Thread - 3 - 获取写锁(writeLock)， 写入数据... Thread - 3 - 释放写锁(writeLock)
1、线程0和线程1都获得了读锁，读取数据;
2、可是线程2获得写锁之后，线程3在线程2释放了写锁之后，才获取写锁，写入数据。
读写锁适用场合
和ReentrantLock适用于一般场合相比，ReadWriteLock适用于读多写少的情况，合理使用可以进一步提高并发效率。
对于ReadWriteLock的介绍就到这里啦，更多java项目中常见问题请继续关注奇Q工具网来进行了解吧。
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