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This is a question asked in one the written that I had given last week can anybody help me identify the difference 

public class TestClass {
    static final  int a = 2;
    static final  int b = 3;

    static int c = 2;
    static int d = 3;

    public static void main(String[ ] args) {
    int product1 = a * b;             //line A
    int product2 = c * d;             //line B
    }
}
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4 Answers 4

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9

Since a and b are declared final, there's the possibility that the compiler will in-line the calculation (the calculation being done at compile time). See the Java Language Specification, section 15.28: Constant Expressions. That doesn't happen with c and d; the product will always be calculated at run time.

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6

Line A is candidate to be computed at compile-time because the fields are final. Line B is computed at runtime.

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1

I believe int product1 = a * b; will be calculated during compilation itself, Since a and b was declared as final.

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0

variables a and b are final so the compiler will replace variables a and b with 2 and 3 in the line product = a * b

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3 Comments

Not quite 'will'. The compiler can choose to inline.
@Bathsheba, isn't there surety of it?
see JLS link in another answer.

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