Java in a Nutshell, 5th Edition

Arrays

An array is a special kind of object that holds zero or more primitive values or references. These values are held in the elements of the array, which are unnamed variables referred to by their position or index. The type of an array is characterized by its element type , and all elements of the array must be of that type.

Array elements are numbered starting with zero, and valid indexes range from zero to the number of elements minus one. The array element with index 1, for example, is the second element in the array. The number of elements in an array is its length. The length of an array is specified when the array is created, and it never changes.

The element type of an array may be any valid Java type, including array types. This means that Java supports arrays of arrays, which provide a kind of multidimensional array capability. Java does not support the matrix-style multidimensional arrays found in some languages.

Array Types

Array types are reference types, just as classes are. Instances of arrays are objects, just as the instances of a class are.^[7] Unlike classes, array types do not have to be defined. Simply place square brackets after the element type. For example, the following code declares three variables of array type:

byte b;                        // byte is a primitive type
byte[] arrayOfBytes;           // byte[] is an array type: array of byte
byte[][] arrayOfArrayOfBytes;  // byte[][] is another type: array of byte[]
String[] points;               // String[] is an array of String objects

The length ...