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April 2000


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April 2000

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Immutables and Multi-valued Returns

Posted by Bill Venners on April 26, 2000 at 1:58 PM

> Hello Bill,

> thanks for answering my question
> > If there is no solution: Why may one make something in Java
> > with arrays, what is forbidden with normal objects?

> Your answer was:
> --snip
> > Class Integer happens to be immutable. Once it is created with
> > a value, it can't change. Arrays are always mutable.
> --snip
> Is there for it a simple reason? I cannot believe that it is so difficult to implement a simple algorithm calculating two or more integers.

1. Immutables are by definition thread-safe.
2. Immutables needn't be cloned before being passed, because
the method to which they are passed can't change their state.

If you want to do a multi-valued return, you'll have to return
an object that contains the values. For an example, search
for "Multi" in the following seminar handout:

This page also discusses immutables.



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