import java.util.Random;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* Created by chengtao on 17/12/5.
* Lock 是替代 sycronized 的，而且sycronized無(wú)法實(shí)現(xiàn)讀寫鎖
*/


public class Thread1201_ReadWriteLock {
public static void main(String[] args) {
final Queue3 q3 = new Queue3();
for(int i=0;i<30;i++)
{
new Thread(){
public void run(){
while(true){
q3.get();
}
}

}.start();

new Thread(){
public void run(){
while(true){
q3.put(new Random().nextInt(10000));
}
}

}.start();
}

}
}

class Queue3{
private Object data = null;//共享數(shù)據(jù)，只能有一個(gè)線程能寫該數(shù)據(jù)，但可以有多個(gè)線程同時(shí)讀該數(shù)據(jù)。
ReadWriteLock rwl = new ReentrantReadWriteLock();
public void get(){
rwl.readLock().lock();
try {
System.out.println(Thread.currentThread().getName() + " 準(zhǔn)備去讀 ----- 數(shù)據(jù)!");
Thread.sleep((long)(Math.random()*10));
System.out.println(Thread.currentThread().getName() + " 已經(jīng)讀到 ----- 數(shù)據(jù) :" + data);
System.out.println();
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
rwl.readLock().unlock();
}
}

public void put(Object data){

rwl.writeLock().lock();
try {
System.out.println(Thread.currentThread().getName() + " 準(zhǔn)備去寫數(shù)據(jù) !");
Thread.sleep((long)(Math.random()*1000));
this.data = data;
System.out.println(Thread.currentThread().getName() + " 已經(jīng)寫入數(shù)據(jù) : " + data);
System.out.println();
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
rwl.writeLock().unlock();
}


}
}
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import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
* Created by chengtao on 17/12/5.
*/
public class Thread1202_ReadWriteLock_Cache {
private Map<String, Object> cache = new HashMap<String, Object>();
public static void main(String[] args) {

}

//讀寫鎖在緩存中的應(yīng)用
private ReadWriteLock rwl = new ReentrantReadWriteLock();
public Object getData(String key){
rwl.readLock().lock();
Object value = null;
try{
value = cache.get(key);
if(value == null){
rwl.readLock().unlock();
rwl.writeLock().lock();
try{
if(value==null){
value = "aaaa";//實(shí)際失去queryDB();
}
}finally{
rwl.writeLock().unlock();
}
rwl.readLock().lock();
}
}finally{
rwl.readLock().unlock();
}
return value;
}
} ?

轉(zhuǎn)載于:https://www.cnblogs.com/ctaixw/p/7979849.html

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