What is a compile time constant in Java? What is the risk of using it?

Question

I assume that constant must be initialized to a constant value at compile time, but following code the return value of ge_const() is assigned to x which will be collected at run time. So this must cause an error but I am getting the output as 50. Can someone clarify the detail?

main()
{
    const int x = get_const();
    printf("%d", x);
}
int get_const()
{
    return 50;
}

Answer 1

Compile time constant and Risk

Compile time constant

public static final variables are known as compile time constant, public is optional there.
They are replaced with actual values at compile time because compiler know their value up-front and also knows that it cannot be changed during run-time.

Risk associate with Compile time constant

Problem with this is that if you are using public static final variable from some in-house or third party library and their value changed later than your client will still be using old value even after you deploy new version of JARs.

To avoid that, make sure you compile your program when you upgrade dependency JAR files.