I was always thoughts arrayObject.length was actual a property, a public final variable of the "array" class and not a method, as a method requires brackets: (). [ July 26, 2007: Message edited by: Gavin Tranter ]
Syntactically, it's an instance member -- i.e., in the code it looks like a variable. But in reality, it is compiled to a special bytecode which returns the length of an array object; it's not a "real" instance member of the array object.
yathamshetti ramchander -- "length" isn't anywhere in the API because it's not a member of any class that's documented in the API. Instead, it's a feature of the Java language. You learn about it from the language specification, or (more likely) from any introductory Java book.
Don't worry that there are many things like this to learn. There is only one similar feature in all of Java -- one other thing that looks like a member variable, but isn't. That's the static "class" member. You can say, for example, "String.class" to get a java.lang.Class object that represents the class java.lang.String.