锁对象Lock-同步问题更完美的处理方式
Lock是java.util.concurrent.locks包下的接口，Lock 实现提供了比使用synchronized 方法和语句可获得的更广泛的锁定操作，它能以更优雅的方式处理线程同步问题，当然也能实现sychronized一样的效果，代码如下：
package org.thread;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class Output {
private Lock lock = new ReentrantLock();
public void output(String name) {
try {
lock.lock();
for (int i = 0; i < name.length(); i++) {
System.out.print(name.charAt(i));
}
} catch (Exception e) {
} finally {
lock.unlock();
}
}
}
现在看看
package org.thread;
public class Outputer {
public synchronized void input(String name){
for(int i =0;i<name.length();i++){
System.out.print(name.charAt(i));
}
}
}
这两个方法其实都是为了实现数据同步
package org.thread;
public class LockTest {
public static void main(String[] args) {
final Outputer outputer = new Outputer();
final Output output = new Output();
Runnable runnable1 = new Runnable() {
public void run() {
outputer.input("Heinrich");
}
};
Runnable runnable2 = new Runnable() {
@Override
public void run() {
outputer.input("AmiLoveMe");
}
};
Runnable runnable3 = new Runnable() {
public void run() {
output.output("Heinrich");
}
};
Runnable runnable4 = new Runnable() {
@Override
public void run() {
output.output("AmiLoveMe");
}
};
new Thread(runnable2).start();
new Thread(runnable1).start();
new Thread(runnable3).start();
new Thread(runnable4).start();
}
}
看看控制台的信息是不是我们想要的,结果肯定是的,反正我觉得是
AmiLoveMeHeinrichHeinrichAmiLoveMe 是我要的结果,有序,数据一致
这样就实现了和sychronized一样的同步效果，需要注意的是，用sychronized修饰的方法或者语句块在代码执行完之后锁自动释放，而是用Lock需要我们手动释放锁，所以为了保证锁最终被释放(发生异常情况)，要把互斥区放在try内，释放锁放在finally内。
如果说这就是Lock，那么它不能成为同步问题更完美的处理方式，下面要介绍的是读写锁(ReadWriteLock)，我们会有一种需求，在对数据进行读写的时候，为了保证数据的一致性和完整性，需要读和写是互斥的，写和写是互斥的，但是读和读是不需要互斥的，这样读和读不互斥性能更高些，来看一下不考虑互斥情况的代码原型：
现在看代码:没有读写锁的
package org.thread;
public class Data {
private Integer data;
public void get() {
System.out.println(Thread.currentThread().getName()+"准备读取数据");
try {
Thread.sleep(4000);
} catch (Exception e) {
}
System.out.println(Thread.currentThread().getName()+"读取"+this.data);
}
public void set(Integer data) {
System.out.println(Thread.currentThread().getName()+"准备写入数据");
try {
Thread.sleep(4000);
} catch (Exception e) {
}
this.data = data;
System.out.println(Thread.currentThread().getName()+"写入"+this.data);
}
}
package org.thread;
import java.util.Random;
public class DataThread {
public static void main(String[] args) {
final Data data = new Data();
for (int i = 0; i < 10; i++) {
Runnable runnable1 = new Runnable() {
@Override
public void run() {
data.set(new Random().nextInt(100));
}
};
new Thread(runnable1).start();
}
for (int i = 0; i < 10; i++) {
Runnable runnable2 = new Runnable() {
@Override
public void run() {
data.get();
}
};
new Thread(runnable2).start();
}
}
}
看看控制台
Thread-0准备写入数据 Thread-8准备写入数据 Thread-5准备写入数据 Thread-4准备写入数据 Thread-3准备写入数据 Thread-2准备写入数据 Thread-7准备写入数据 Thread-1准备写入数据 Thread-6准备写入数据 Thread-9准备写入数据 Thread-10准备读取数据 Thread-12准备读取数据 Thread-11准备读取数据 Thread-14准备读取数据 Thread-15准备读取数据 Thread-16准备读取数据 Thread-13准备读取数据 Thread-17准备读取数据 Thread-18准备读取数据 Thread-19准备读取数据 Thread-7写入28 Thread-3写入56 Thread-8写入83 Thread-2写入88 Thread-9写入83 Thread-5写入88 Thread-0写入84 Thread-6写入28 Thread-1写入28 Thread-4写入28 Thread-19读取56 Thread-12读取56 Thread-14读取56 Thread-13读取56 Thread-16读取56 Thread-10读取56 Thread-11读取56 Thread-15读取56 Thread-17读取56 Thread-18读取56
我们要实现写入和写入互斥，读取和写入互斥，读取和读取互斥，在set和get方法加入
synchronized修饰符
package org.thread;
public class Data {
private Integer data;
public synchronized void get() {
System.out.println(Thread.currentThread().getName()+"准备读取数据");
try {
Thread.sleep(4000);
} catch (Exception e) {
}
System.out.println(Thread.currentThread().getName()+"读取"+this.data);
}
public synchronized void set(Integer data) {
System.out.println(Thread.currentThread().getName()+"准备写入数据");
try {
Thread.sleep(4000);
} catch (Exception e) {
}
this.data = data;
System.out.println(Thread.currentThread().getName()+"写入"+this.data);
}
}
Thread-0准备写入数据 Thread-0写入54 Thread-19准备读取数据 Thread-19读取54 Thread-18准备读取数据 Thread-18读取54 Thread-17准备读取数据 Thread-17读取54 Thread-16准备读取数据 Thread-16读取54 Thread-15准备读取数据 Thread-15读取54 Thread-14准备读取数据 Thread-14读取54 Thread-13准备读取数据 Thread-13读取54 Thread-12准备读取数据 Thread-12读取54 Thread-11准备读取数据 Thread-11读取54 Thread-10准备读取数据 Thread-10读取54 Thread-9准备写入数据 Thread-9写入42 Thread-8准备写入数据 Thread-8写入86 Thread-1准备写入数据 Thread-1写入30 Thread-2准备写入数据 Thread-2写入3 Thread-4准备写入数据 Thread-4写入81 Thread-3准备写入数据 Thread-3写入72 Thread-5准备写入数据 Thread-5写入15 Thread-6准备写入数据 Thread-6写入16 Thread-7准备写入数据 Thread-7写入33
我们发现，虽然写入和写入互斥了，读取和写入也互斥了，但是读取和读取之间也互斥了，不能并发执行，效率较低，用读写锁实现代码如下：
package org.thread;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class DataSyn {
private Integer data;
private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
public void get() {
System.out.println(Thread.currentThread().getName() + "准备读取数据");
readWriteLock.readLock().lock();;
try {
Thread.sleep(2000);
System.out.println(Thread.currentThread().getName() + "正在读取数据"
+ this.data);
} catch (Exception e) {
} finally {
readWriteLock.readLock().unlock();
}
}
public void set(Integer data) {
System.out.println(Thread.currentThread().getName() + "准备写入数据");
readWriteLock.writeLock().lock();;
try {
this.data = data;
System.out.println(Thread.currentThread().getName()+"正在写入"+data);
} catch (Exception e) {
e.printStackTrace();
}finally{
readWriteLock.writeLock().unlock();
}
}
}
Thread-5准备写入数据 Thread-5正在写入85 Thread-1准备写入数据 Thread-1正在写入74 Thread-6准备写入数据 Thread-6正在写入28 Thread-0准备写入数据 Thread-0正在写入93 Thread-3准备写入数据 Thread-4准备写入数据 Thread-7准备写入数据 Thread-8准备写入数据 Thread-3正在写入75 Thread-2准备写入数据 Thread-2正在写入75 Thread-4正在写入70 Thread-7正在写入65 Thread-9准备写入数据 Thread-8正在写入92 Thread-9正在写入88
这个是不是效率更好了,当然咯,要不然说这么多干什么