6、读写锁
ReadWriteLock
package com.bjw.rw;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/*
独占锁(写锁)
共享锁(读锁)
* ReadWriteLock
* 读-读 可以共存
* 读-写 不能共存
* 写-写 不能共存
* */
public class ReadWriteLockDemo {
public static void main(String[] args) {
MyCacheLock myCache = new MyCacheLock();
//写入
for (int i = 1; i <= 5; i++) {
final int temp = i;
new Thread(()->{
myCache.put(temp+"",temp+"");
},String.valueOf(i)).start();
}
//读取
for (int i = 1; i <= 5; i++) {
final int temp = i;
new Thread(()->{
myCache.get(temp+"");
},String.valueOf(i)).start();
}
}
}
/*
* 自定义缓存
* */
class MyCache {
private volatile Map<String, Object> map = new HashMap<>();
//存
public void put(String key, Object value) {
System.out.println(Thread.currentThread().getName()+"写入"+key);
map.put(key, value);
System.out.println(Thread.currentThread().getName()+"写入OK");
}
//取
public void get(String key) {
System.out.println(Thread.currentThread().getName()+"读取"+key);
Object o = map.get(key);
System.out.println(Thread.currentThread().getName()+"读取OK");
}
}
//加锁的
class MyCacheLock {
private volatile Map<String, Object> map = new HashMap<>();
private ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();
//存,写入的时候,只希望同时只有一个线程写
public void put(String key, Object value) {
readWriteLock.writeLock().lock();
try {
System.out.println(Thread.currentThread().getName()+"写入"+key);
map.put(key, value);
System.out.println(Thread.currentThread().getName()+"写入OK");
} catch (Exception e) {
e.printStackTrace();
} finally {
readWriteLock.writeLock().unlock();
}
}
//取,读,所有人都可以读!
public void get(String key) {
readWriteLock.readLock().lock();
try {
System.out.println(Thread.currentThread().getName()+"读取"+key);
Object o = map.get(key);
System.out.println(Thread.currentThread().getName()+"读取OK");
} catch (Exception e) {
e.printStackTrace();
} finally {
readWriteLock.readLock().unlock();
}
}
}
7、阻塞队列BlockingQueue
什么情况下会使用阻塞队列
多线程并发处理,线程池!
四组API
1、抛出异常
2、不会抛出异常
3、阻塞 等待
4、超时等待
SynchronousQueue
没有容量
进去一个元素,必须等待取出来之后,才能再往里面放一个元素
put ————————————take