The Java® Language Specification, Java SE 7 Edition, Fourth Edition

14.21. Unreachable Statements

It is a compile-time error if a statement cannot be executed because it is unreachable.

This section is devoted to a precise explanation of the word “reachable.” The idea is that there must be some possible execution path from the beginning of the constructor, method, instance initializer, or static initializer that contains the statement to the statement itself. The analysis takes into account the structure of statements. Except for the special treatment of while, do, and for statements whose condition expression has the constant value true, the values of expressions are not taken into account in the flow analysis.

For example, a Java compiler will accept the code:

{    int n = 5;    while (n > 7) k = 2;}

even though ...