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Thread: Type casting error in Java

  1. #1
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    Default Type casting error in Java

    I am learning java (or should I say, filling in the holes) from a reputable learning source (say no more) it said, if fact I am going to feed it back to source I made my purchase from, they said

    int myInt;
    long myLong = 123987654321L;
    myInt = (int) (myLong);
    saying that the number might be chopped

    I thought why not give it a go, to find myInt comes out to be -566397263
    Well one thing I learnt, never trust down type casting.
    Last edited by Eric; December 7th, 2008 at 01:09 PM. Reason: in red added


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    Default Re: type casting fibs

    Quote Originally Posted by Eric View Post
    Well one thing I learnt, never trust down type casting.
    Downcasting should only be done where it can be trusted - generally only at system boundaries where objects are being generated and introduced to the system.

    But casting a long to an int is not downcasting, it is a 'casting conversion' (specifically a narrowing primitive conversion). Downcasting is when you cast a superclass type to a subclass type.

    A narrowing primitive conversion is converting a larger primitive numeric type to a smaller one. For full details, see Narrowing Primitive Conversions.

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    Default Re: type casting fibs

    Now I am not sure why I posted this thread?

    I suppose the best idea might be to test to see if that Long variable could fit down into a Int, and if it is outside the range of -2147483648 to 2147483647 print off something like "done but with error!"

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    Default Re: type casting fibs


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