关于lock锁

在 jdk1.5 之后，并发包中新增了 Lock 接口(以及相关实现类)用来实现锁功能，Lock 接口提供了与 synchronized 关键字类似的同步功能，但需要在使用时手动获取锁和释放锁。

lock锁也叫显示锁

大家看下这个lock锁:

lock是个接口

这个接口下面很多锁：

对于lock锁的使用，实现生产者消费者模式的：

package com.toov5.thread;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

//共享对象

class ResLock {

    public boolean flag = true;

    public String sex;

    public String name;

    public Lock lock = new ReentrantLock();

}

class inputThreadLock extends Thread {

    public ResLock res;

    public inputThreadLock(ResLock res) {

        this.res = res;

    }

    @Override

    public void run() {

        int count = 0;

        while (true) {

            try {

                res.lock.lock();

                if (count == 0) {

                    res.name = "lucy";

                    res.sex = "girl";

                } else {

                    res.name = "Jack";

                    res.sex = "boy";

                }

            count = (count + 1) % 2;

            } catch (Exception e) {

            }finally{

                res.lock.unlock();  //释放锁写在finally里面

            }

        }

    }

}

class readThreadLock extends Thread {

    public ResLock res;

    public readThreadLock(ResLock res) {

        this.res = res;

    }

    @Override

    public void run() {

        while (true) {

            try {

                res.lock.lock();

                System.out.println(res.name + "," + res.sex);

            } catch (Exception e) {

                e.printStackTrace();

            }finally {

                res.lock.unlock();

            }

        }

    }

}

public class LockTest {

    public static void main(String[] args) {

        Res res = new Res();

        inputThread inputThread = new inputThread(res);

        readThread  readThread = new readThread(res);

        inputThread.start();

        readThread.start();

    }

}

注意 unlock写到finally里面哦

然后lock锁里面的类似于 notify 和 wait的 Condition

Condition的功能类似于在传统的线程技术中的,Object.wait()和Object.notify()的功能。

使用方法：

package com.toov5.thread;

import java.util.concurrent.locks.Condition;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

//共享对象

class ResLock {

    public boolean flag = true;

    public String sex;

    public String name;

    public Lock lock = new ReentrantLock();

    public Condition condition  = lock.newCondition();

}

class inputThreadLock extends Thread {

    public ResLock res;

    public inputThreadLock(ResLock res) {

        this.res = res;

    }

    @Override

    public void run() {

        if (res.flag) {

            try {

                res.condition.await();

            } catch (InterruptedException e) {

                e.printStackTrace();

            }

        }

        int count = 0;

        while (true) {

            try {

                res.lock.lock();

                if (count == 0) {

                    res.name = "lucy";

                    res.sex = "girl";

                } else {

                    res.name = "Jack";

                    res.sex = "boy";

                }

            count = (count + 1) % 2;

            res.flag=true;

            res.condition.signal();

            } catch (Exception e) {

            }finally{

                res.lock.unlock();  //释放锁写在finally里面

            }

        }

    }

}

class readThreadLock extends Thread {

    public ResLock res;

    public readThreadLock(ResLock res) {

        this.res = res;

    }

    @Override

    public void run() {

        while (true) {

            try {

                res.lock.lock();

                if (res.flag) {

                    res.condition.await();

                }

                System.out.println(res.name + "," + res.sex);

                res.condition.signal();

            } catch (Exception e) {

                e.printStackTrace();

            }finally {

                res.lock.unlock();

            }

        }

    }

}

public class LockTest {

    public static void main(String[] args) {

        Res res = new Res();

        inputThread inputThread = new inputThread(res);

        readThread  readThread = new readThread(res);

        inputThread.start();

        readThread.start();

    }

}

执行结果：

Lock与synchronized 关键字的区别

Lock 接口可以尝试非阻塞地获取锁当前线程尝试获取锁。如果这一时刻锁没有被其他线程获取到，则成功获取并持有锁。
Lock 接口能被中断地获取锁与 synchronized 不同，获取到锁的线程能够响应中断，当获取到的锁的线程被中断时，中断异常将会被抛出，同时锁会被释放。

Lock 接口在指定的截止时间之前获取锁，如果截止时间到了依旧无法获取锁，则返回。

synchronize重量级锁不可控制释放锁遇到异常或者代码执行完毕后释放锁

lock轻量级可控释放锁更灵活一些 lock是1.5出来的比synchronize晚弥补了一些不足还有读写锁重入锁功能要强大一些

巴特西

关于lock锁

Lock与synchronized 关键字的区别

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