一、Java锁机制

1.Synchronized重入锁

public class Test001 implements Runnable {

	@Override
	public void run() {
		set();
	}
	
	public synchronized  void set() {
		System.out.println("name:" + Thread.currentThread().getName() + " set();");
		get();
	}
	
	public  synchronized void get() {
		System.out.println("name:" + Thread.currentThread().getName() + " get();");

	}

	public static void main(String[] args) {
		Test001 test001 = new Test001();
		Thread t1 = new Thread();
		t1.start();
	}
}

2.ReentrantLock重入锁

// 演示Lock锁是否具备 可重入性 特征：锁可以传递（方法递归传递）
public class Test02 extends Thread {
	Lock lock = new ReentrantLock();
	
	@Override
	public void run() {
		set();
	}
	
	public void set() {
		try {
			lock.lock();
			System.out.println(Thread.currentThread().getId());
			get();
		} catch (Exception e) {
			
		} finally {
			lock.unlock();
		}
	}
	
	public void get() {
		try {
			lock.lock();
			System.out.println(Thread.currentThread().getId());
		} catch (Exception e) {
			
		} finally {
			lock.unlock();
		}
	}

	public static void main(String[] args) {
		Test02 Test02 = new Test02();
		Test02.start();
	}

}

3.ReentrantReadWriteLock读写锁

package com.itmayiedu;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;

public class Cache {
	private ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();

	private volatile Map<String, String> map = new HashMap<>();
	private ReadLock readLock = rwl.readLock();
	private WriteLock writeLock = rwl.writeLock();

	public String get(String key) {

		try {
			readLock.lock();
			System.out.println("正在做读的操作,key:" + key + "开始..");
			Thread.sleep(100);
			String value = map.get(key);
			System.out.println("正在做读的操作,key:" + key + "结束..");
			return value;
		} catch (Exception e) {
			return null;
		}finally {
			readLock.unlock();
		}
		
	
	}

	public void put(String key, String value) {
		try {
			writeLock.lock();
			System.out.println("正在做写的操作,key:" + key + ",value:" + value + "开始..");
				Thread.sleep(100);
			map.put(key, value);
			System.out.println("正在做写的操作,key:" + key + ",value:" + value + "結束..");
		} catch (Exception e) {
			
		}finally {
			writeLock.unlock();
		}
	}

	public static void main(String[] args) {
		new Thread(new Runnable() {

			@Override
			public void run() {
				for (int i = 1; i <= 10; i++) {
					Cache.put(i + "", "i:" + i);
				}

			}
		}).start();

		new Thread(new Runnable() {

			@Override
			public void run() {
				for (int i = 1; i <= 10; i++) {
					Cache.get(i + "");
				}
			}
		}).start();
	}

}

4.乐观锁

在这里插入图片描述

5.悲观锁

在这里插入图片描述

6.AtomicInteger原子类

public class Test0001 implements Runnable {
//	private static Integer count = 1;
	private static AtomicInteger atomic = new AtomicInteger();

	@Override
	public void run() {
		while (true) {
			int count = getCountAtomic();
			System.out.println(count);
			if (count >= 150) {
				break;
			}
		}
	}
/*
	public synchronized Integer getCount() {
		try {
			Thread.sleep(50);
		} catch (Exception e) {
			// TODO: handle exception
		}

		return count++;
	}
*/
	public Integer getCountAtomic() {
		try {
			Thread.sleep(50);
		} catch (Exception e) {
			// TODO: handle exception
		}
		return atomic.incrementAndGet();
	}

	public static void main(String[] args) {
		Test0001 test0001 = new Test0001();
		Thread t1 = new Thread(test0001);
		Thread t2 = new Thread(test0001);
		t1.start();
		t2.start();
	}

}

7.Java内存模型回顾

在这里插入图片描述

8.CAS无锁机制原理

在这里插入图片描述