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.
Why Is A Negative Number Called Absolute Zero? Those who have studied some physics might remember why minus 459.67 Fahrenheit is called absolute zero, but for the rest, it's probably a bit confusing. Switching to Celsius won't help; absolute zero is minus 273.15 degrees on that scale. Is absolute zero ever zero degrees? To find the answer, one needs to look to a scientific temperature scale called Kelvin and how it evolved.