Chapter 10. Arrays
要明白elementtype与componenttype
There are some situations in which an element of an array can be an array: if the element type is Object or Cloneable or java.io.Serializable, then some or all of the elements may be arrays, because any array object can be assigned to any variable of these types.
If an array variable v has type A[], where A is a reference type, then v can hold a reference to an instance of any array type B[], provided B can be assigned to A (§5.2). This may result in a run-time exception on a later assignment; see §10.5 for a discussion.
Arrays must be indexed by int values; short, byte, or char values may also be used as index values because they are subjected to unary numeric promotion (§5.6.1) and become int values.
An attempt to access an array component with a long index value results in a compile-time error.