CHAPTER 10

Arrays

Even Solomon in all his glory was not arrayed like one of these.
—Matthew 6:29

Java arrays are objects (§4.3.1), are dynamically created, and may be assigned to variables of type Object (§4.3.2). All methods of class Object may be invoked on an array.

An array object contains a number of variables. The number of variables may be zero, in which case the array is said to be empty. The variables contained in an array have no names; instead they are referenced by array access expressions that use nonnegative integer index values. These variables are called the components of the array. If an array has n components, we say n is the length of the array; the components of the array are referenced using integer indices from 0 to , inclusive.

All the components of an array have the same type, called the component type of the array. If the component type of an array is T, then the type of the array itself is written T[].

The component type of an array may itself be an array type. The components of such an array may contain references to subarrays. If, starting from any array type, one considers its component type, and then (if that is also an array type) the component type of that type, and so on, eventually one must reach a component type that is not an array type; this is called the element type of the original array, and the components at this level of the data structure are called the elements of the original array.

There is one situation in which an element of an array can be an array: if the element type is Object, then some or all of the elements may be arrays, because any array object can be assigned to any variable of type Object.