Re: JavaMemoryModel: Mutually exclusive goals for Java memory model

From: Bill Pugh (
Date: Mon Apr 22 2002 - 12:29:02 EDT

At 5:22 PM -0700 4/18/02, Thomas Wang wrote:
>Also, refresh my memory about how should we write immutable object source
>codes now? (under the new memory model)

OK, here is a guideline for creating immutable objects under the new
memory model:

If you want an object X to be immutable in the presence of data races
by uses of the object:

  * every field of X should be final
  * any data structure reachable from fields of X should be either:
        - immutable, or
        - only reachable by threads other than the creating
          thread via fields of object X

For example, String will contain a final reference to a character
array, and the only way for another thread to see that character
array is through the final reference.

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