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Casting Object[] to String[]

Pho Tek
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Joined: Nov 05, 2000
Posts: 782

Why can't I cast an Object[] to String[] ?


Rob Ross

Joined: Jan 07, 2002
Posts: 2205
Have you tried it with an explicit cast?

SCJP 1.4
Ilja Preuss

Joined: Jul 11, 2001
Posts: 14112
Originally posted by Pho Tek:
Why can't I cast an Object[] to String[] ?

How did you try? Can you show us some code? What is the Object[] containing?

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frank davis
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Joined: Feb 12, 2001
Posts: 1479
Originally posted by Ilja Preuss:

How did you try? Can you show us some code? What is the Object[] containing?

Doesn't that type of casting cause a ClassCastException error at runtime if the Object is not actually a String object?
Jim Yingst

Joined: Jan 30, 2000
Posts: 18671
It doesn't matter what the Object[] is containing - if it was created using new Object[], it really is an Object[] array even if all the elements are Strings. No Amount of casting can change this. However, if the array is really a String[] (created using new String[] for example) and you're just using a reference variable of type Object[] to refer to it, then you can cast. E.g.will compile OK, but will throw a ClassCastException at runtime because the array is not a String[] - just an Object[] containing Strings. However this works:
This illustrates why the cast in the previous example was allowed to succeed at compile time - a reference which is declared to be of type Object[] could hold a reference to a String[] (as it does in the second example). So the cast must be allowed at compile time - but it can still be invalid at run time.
This may seem strange, but it's nearly identical to the waycompiles but does not run, and compiles and runs.
[ May 30, 2002: Message edited by: Jim Yingst ]

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I agree. Here's the link:
subject: Casting Object[] to String[]
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