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How to identify compile time constants

 
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Hi All,

I found
final int a=10;//line 1 is compile time constant
but,
final int b;//line 1
b=5; // line 2
here b is not a compile time constant
why? please explain

Thanks
Abhishek
 
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why? please explain



There is nothing to explain for the left hand side of the assignment, the compiler requires that the declaration be final, be either a primitive type or a string, and be initialized during the declaration.

For the right hand side -- the expression that will be assigned -- it's a bit more complex. The compiler requires that it be assigned a constant expression. If the RHS is not a constant expression, then the declared variable is not a compile time constant.

See section 15.28, for the definition of constant expression:

http://java.sun.com/docs/books/jls/second_edition/html/expressions.doc.html

Henry
 
Dash Abhisek
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Thanks
 
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