Compile Time Constants...

[Dan Silva]

What does it mean to be a compile time constant?

[Ben Souther]

A compile time constant is one that can't be set or changed after compilation.

Examples:

 
final int COMPILE_TIME_CONSTANT = 1;
 
final int SET_AT_RUNTIME;
 
// constructor
public MyClass(int intValue){
  this.SET_AT_RUNTIME = intValue.
}
 
or 
 
final int SET_AT_RUNTIME = Constants.SET_AT_RUNTIME;

The first is a compile time constant.
The compiler knows that the value will be 1 and that it can never change.

In the second example the assignment of SET_AT_RUNTIME is delayed until the construction of the class. The compiler has no idea what SET_AT_RUNTIME will be.

In the third example the value depends on another class which could change after this class has been compiled so it isn't a compile time constant.
[ March 01, 2008: Message edited by: Ben Souther ]

[Dan Silva]

Thanks!