synchronized锁和ReentrantLock锁的使用

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.stereotype.Service;

/**
 * @author: xiepanpan
 * @Date: 2020/2/17
 * @Description:
 */
@Service
public class RedisIncrService {

    @Autowired
    StringRedisTemplate redisTemplate;

	private Object obj = new Object();
	//这个锁大家都用一个。
    //this当前对象。当前service对象。spring的组件是单例的。this一个。
    //this相同，锁相同，锁ok
    //RedisIncrService对象一个。自动注入；StringRedisTemplate，redisTemplate也只能注入唯一一个。
    //RedisIncrService对象创建的时候赋值，RedisIncrService一个   private Object obj = new Object();

    //1）、synchronized(this)：能
    //2）、synchronized (redisTemplate)：能
    //3）、synchronized (new Object())：锁不住
    //4）、synchronized (obj)：锁得住？锁得住
    //5）、synchronized (obj())；锁的住
    //6）、synchronized (RedisIncrService.class)；锁得住
    public void incr() {
        synchronized (this){
            ValueOperations<String, String> stringStringValueOperations = redisTemplate.opsForValue();
            String num = stringStringValueOperations.get("num");
            if(num!=null){
                Integer i = Integer.parseInt(num);
                i = i+1;
                stringStringValueOperations.set("num",i.toString());
            }
        }
    }

	public Object obj() {
        
        return obj;
    }
     //肯定锁不住
    //public Object obj() {
    //    Object o = new Object();
    //    BeanUtils.copyProperties(obj, o);
    //    return o;
    //}

}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.stereotype.Service;

/**
 * @author: xiepanpan
 * @Date: 2020/2/17
 * @Description:
 */
@Service
public class RedisIncrService {

    @Autowired
    StringRedisTemplate redisTemplate;
    
	ReentrantLock lock = new ReentrantLock();

	
    public void incr() {

        /**
         *  ReentrantLock lock = new ReentrantLock();应该在成员变量位置才锁得住
         */

        //锁得住？
        lock.lock();
        ValueOperations<String, String> stringStringValueOperations = redisTemplate.opsForValue();
        String num = stringStringValueOperations.get("num");
        if (num != null) {
            Integer i = Integer.parseInt(num);
            i = i + 1;
            stringStringValueOperations.set("num", i.toString());
        }

        lock.unlock();

       
    }

}