Question

when I have a method like

public void unsynchronizedMethod(){
  callSynchronizedMethod();
  //dosomestuff after this line
}

does it mean that all content, after calling callSynchronizedMethod() in the unsynchronizedMethod()-Method, is implicitly synchronized?

Answer 1

Synchronization is defined in a straightforward manner:

• For a synchronized method: within the execution of that method
• For a synchronized block: within the execution of that block

Here are the relevant excerpts from Java Language Specification 3rd Edition:

JLS 14.19 The synchronized Statement

A synchronized statement:

1. acquires a mutual-exclusion lock on behalf of the executing thread,
2. executes a block,
3. then releases the lock.

While the executing thread owns the lock, no other thread may acquire the lock.

synchronized methods is semantically identical to a synchronized statement applied to the whole method (§JLS 8.4.3.6. The lock is obtained from either this (if it’s an instance method) or the Class object associated with the method’s class (if it’s a static method; you can’t refer to this in a static context).

So to answer the original question, given this snippet:

public void unsynchronizedMethod(){
  callSynchronizedMethod();

  doSomeUnsynchronizedStuff(); // no "implicit synchronization" here
}

Note that this is by design: you should always strive to minimize synchronization to only critical sections. Outside of those critical sections, there is no lingering effect from earlier synchronization.

See also

• Effective Java 2nd Edition, Item 67: Avoid excessive synchronization

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