一、介绍
二、代码演示
1. 不使用读写锁
package readwritelock;
import java.util.HashMap;
import java.util.Map;
/**
* @author swaggyhang
* @create 2023-07-09 11:16
*/
public class Test01 {
public static void main(String[] args) {
MyCache myCache = new MyCache();
for (int i = 1; i <= 5; i++) {
final int temp = i;
new Thread(() -> {
myCache.put(temp + "", temp);
}, String.valueOf(i)).start();
}
for (int i = 1; i <= 5; i++) {
final int temp = i;
new Thread(() -> {
myCache.get(temp + "");
}, String.valueOf(i)).start();
}
}
}
class MyCache {
private volatile Map<String, Object> map = new HashMap<>();
// 存入
public void put(String key, Object value) {
System.out.println("线程" + Thread.currentThread().getName() + ":写入 => " + key);
map.put(key, value);
System.out.println("线程" + Thread.currentThread().getName() + ":写入OK ");
}
// 取出
public void get(String key) {
System.out.println("线程" + Thread.currentThread().getName() + ":取出 => " + key);
Object o = map.get(key);
System.out.println("线程" + Thread.currentThread().getName() + ":取出OK");
}
}
2. 使用读写锁
package readwritelock;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* @author swaggyhang
* @create 2023-07-09 11:27
*/
public class Test02 {
public static void main(String[] args) {
MyCacheLock myCacheLock = new MyCacheLock();
for (int i = 1; i <= 5; i++) {
final int temp = i;
new Thread(() -> {
myCacheLock.put(temp + "", temp);
}, String.valueOf(i)).start();
}
for (int i = 1; i <= 5; i++) {
final int temp = i;
new Thread(() -> {
myCacheLock.get(temp + "");
}, String.valueOf(i)).start();
}
}
}
class MyCacheLock {
private volatile Map<String, Object> map = new HashMap<>();
// 读写锁,更加细粒度的控制
private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
// 存入,写入的时候,只希望同时只有一个线程写入
public void put(String key, Object value) {
readWriteLock.writeLock().lock();
try {
System.out.println("线程" + Thread.currentThread().getName() + ":写入 => " + key);
map.put(key, value);
System.out.println("线程" + Thread.currentThread().getName() + ":写入OK ");
} finally {
readWriteLock.writeLock().unlock();
}
}
// 取出,读取的时候,所有人都可以读取
public void get(String key) {
readWriteLock.readLock().lock();
try {
System.out.println("线程" + Thread.currentThread().getName() + ":取出 => " + key);
Object o = map.get(key);
System.out.println("线程" + Thread.currentThread().getName() + ":取出OK");
} finally {
readWriteLock.readLock().unlock();
}
}
}
三、总结
-
ReadWriteLock读写锁特点
① 写锁是独占锁,一次只能被一个线程占有
② 读锁是共享锁,多个线程可以同时占有 -
读-读:可以共存
-
读-写:不能共存文章来源:https://www.toymoban.com/news/detail-537153.html
-
写-写:不能共存文章来源地址https://www.toymoban.com/news/detail-537153.html
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