For example, if a thrown exception object has class IllegalArgumentException, that indicates someone passed an illegal argument to a method. Sometimes you will want to indicate that a method encountered an abnormal condition that isn't represented by a class in the Throwable family of java.lang.
Actually, zero is neither a negative or a positive number. The whole idea of positive and negative is defined in terms of zero. Negative numbers are numbers that are smaller than zero, and positive numbers are numbers that are bigger than zero. Since zero isn't bigger or smaller than itself (just like you're not older than yourself, or taller than yourself), zero is neither positive nor negative.
Zero (real name David Oh, and formerly known as O, Major Tom, Major Zero and Cipher) was the original commander of CIA Special Forces Unit FOX (Force Operation X). After Zero became a founding member of the Patriots along with Big Boss, the two friends would later develop a bitter enmity.