线程同步:
- 是因为多线程读写竞争资源需要同步
- Java语言提供了synchronized/wait/notify
- 编写多线程同步很困难
所以Java提供了java.util.concurrent包:
- 更高级的同步功能
- 简化多线程程序的编写
- JDK>= 1.5
java.util.locks.ReetrantLock用于替代synchronized加锁
```#java
synchronized(lockObj){
n = n + 1;
}
final Lock lock = new ReetrantLock()
lock.lock()
try{
n = n + 1;
}finally{
lock.unlock();
}
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Lock;
class Counter{
private Lock lock = new ReentrantLock();
private int value = 0;
public void add(int m){
lock.lock();
try{
value += m;
}finally {
lock.unlock();
}
}
public void dec(int m){
lock.lock();
try{
value -= m;
}finally {
lock.unlock();
}
}
public int get(){
lock.lock();
try{
return this.value;
}finally {
lock.unlock();
}
}
}
public class Main{
final static int LOOP = 100;
public static void main(String[] args) throws Exception{
Counter counter = new Counter();
Thread t1 = new Thread(){
public void run(){
for(int i=0;i<LOOP;i++){
counter.add(1);
}
}
};
Thread t2 = new Thread(){
public void run(){
for(int i=0;i<LOOP;i++){
counter.dec(1);
}
}
};
t1.start();
t2.start();
t1.join();
t2.join();
System.out.println(counter.get());
}
}
tryLock()可指定超时
总结:
ReentrantLock可以替代synchronized
ReentrantLock获取锁更安全
获取锁在try...finally之前
必须使用try... finallu保证正确释放锁
原文地址:https://www.cnblogs.com/csj2018/p/11007060.html
时间: 2024-10-03 07:34:24