BLOCKS AND STATEMENTS

Unreachable Statements

14.19

The rationale for this differing treatment is to allow programmers to define

 flag variables  such as:

static final boolean DEBUG = false;

and then write code such as:

if (DEBUG) { x=3; }

The idea is that it should be possible to change the value of

DEBUG

 from

false

 to

true

 or from

true

 to

false

 and then compile the code correctly with no other

changes to the program text.

This ability to  conditionally compile  has a significant impact on, and rela 

tionship to, binary compatibility ( 13). If a set of classes that use such a  flag 

variable are compiled and conditional code is omitted, it does not suffice later to

distribute just a new version of the class or interface that contains the definition of

the flag. A change to the value of a flag is, therefore, not binary compatible with

preexisting binaries ( 13.4.8). (There are other reasons for such incompatibility as

well, such as the use of constants in

case

 labels in

switch

 statements; see

 13.4.8.)

One ought not to be thrown into confusion

By a plain statement of relationship . . .

 Robert Frost,

The Generations of Men

 (1914)

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