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.
In the graph below, x 0 = -1 is negative, so the vertex is moved one unit to the left. The equation, however, looks as though we are adding 1 to x: In other words, In short, positive values added to x in the equation move the graph to the left, toward more negative values. The value of x 0 is negative, but the appearance of the number in the equation is positive. This takes some practice to remember.