为什么使用ReentrantLock可以使用synchronized（this）？(Why use a ReentrantLock if one can use synchronized(this)?)

 我正在想知道如果可以使用synchronized (this) ，并发锁是如此重要。 在下面的虚拟代码中，我可以做： 
 
 
 
 同步整个方法或同步脆弱的区域（synchronized（this）{...}） 
 
 
 或者使用ReentrantLock锁定易受攻击的代码区域。 
 
 
 码： 
 
private final ReentrantLock lock =  new ReentrantLock(); 
    private static List<Integer> ints;

    public Integer getResult(String name) { 
        .
        .
        .
        lock.lock();
        try{
            if (ints.size()==3) {
                ints=null;
                return -9;
            }   

            for (int x=0; x<ints.size(); x++) {
                System.out.println("["+name+"] "+x+"/"+ints.size()+". values >>>>"+ints.get(x));
            }

        }finally {
            lock.unlock();
        } 
        return random;
}

I'm trying to understand what makes the lock in concurrency so important if one can use synchronized (this). In the dummy code below, I can do either:
 
 
 
synchronized the entire method or synchronize the vulnerable area (synchronized(this){...})
 
 
OR lock the vulnerable code area with a ReentrantLock.
 
 
Code:
 
    private final ReentrantLock lock = new ReentrantLock(); 
    private static List<Integer> ints;

    public Integer getResult(String name) { 
        .
        .
        .
        lock.lock();
        try {
            if (ints.size()==3) {
                ints=null;
                return -9;
            }   

            for (int x=0; x<ints.size(); x++) {
                System.out.println("["+name+"] "+x+"/"+ints.size()+". values >>>>"+ints.get(x));
            }

        } finally {
            lock.unlock();
        } 
        return random;
}

原文：https://stackoverflow.com/questions/11821801