使用同步方法而不是同步块有优势吗? [英] Is there an advantage to use a Synchronized Method instead of a Synchronized Block?

问题描述

谁能用一个例子告诉我同步方法相对于同步块的优势?

Can any one tell me the advantage of synchronized method over synchronized block with an example?

推荐答案

谁能通过一个例子告诉我同步方法相对于同步块的优势?谢谢.

与块相比，使用同步方法没有明显的优势.

There is not a clear advantage of using synchronized method over the block.

也许唯一的(但我不会称其为优势)是您不需要包含对象引用 this.

Perhaps the only one ( but I wouldn't call it an advantage ) is you don't need to include the object reference this.

方法:

public synchronized void method() { // blocks "this" from here.... 
    ...
    ...
    ...
} // to here

阻止:

public void method() { 
    synchronized( this ) { // blocks "this" from here .... 
        ....
        ....
        ....
    }  // to here...
}

看到了吗?一点优势都没有.

See? No advantage at all.

块do虽然比方法有优势，主要是在灵活性方面，因为你可以使用另一个对象作为锁，而同步方法会锁定整个对象.

Blocks do have advantages over methods though, mostly in flexibility because you can use another object as lock whereas syncing the method would lock the entire object.

比较:

// locks the whole object
... 
private synchronized void someInputRelatedWork() {
    ... 
}
private synchronized void someOutputRelatedWork() {
    ... 
}

对比

// Using specific locks
Object inputLock = new Object();
Object outputLock = new Object();

private void someInputRelatedWork() {
    synchronized(inputLock) { 
        ... 
    } 
}
private void someOutputRelatedWork() {
    synchronized(outputLock) { 
        ... 
    }
}

此外，如果方法增长，您仍然可以保持同步部分分开:

Also if the method grows you can still keep the synchronized section separated:

 private void method() {
     ... code here
     ... code here
     ... code here
    synchronized( lock ) { 
        ... very few lines of code here
    }
     ... code here
     ... code here
     ... code here
     ... code here
}

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