What is constant folding in java compiler? [duplicate]

Question

Possible Duplicate:
is there any concept called “Constant Folding” in java?

Hi I have come across line Java compiler uses something known as Constant Folding.What is this? and how Does it affect?

Answer 1

Constant folding is where the compiler finds expressions that contain compile-time constants and replaces them with the result effectively removing redundant runtime calculations.

// code
static final int a = 2;
int b = 30 * a;

// folding would create
int b = 60;