Unreachable code

Unreachable code is a section of code in a program that can never be executed. 
Having unreachable code is bad because it wastes space on the disk, memory, and CPU cache.
Luckily, many modern compilers alert the programmer with a warning or error whenever it detects unreachable code.
Example.
 void beepForever() {
 while (true) {
 System.out.println("Beep!");
 System.out.println(":'(");
 
In this example, ":'(" will never be printed because the loop never exits.