<> The first 9 chapter array
Array is a very important set type in computer language , In most computer languages, arrays have the following three basic characteristics ：
1. uniformity ： Arrays can only hold elements of the same data type , The data type of an element can be any of the same data types .
2. Order ： Elements in an array are ordered , Access by subscript .
3. Immutability ： Once the array is initialized , Length （ Number of elements in the array ） Immutable .
stay Java The subscript of the array in is zero based , In fact, in many computer languages, array subscripts start at zero .Java Array subscript access operator is bracket , as intArray, Indicates access intArray First element of array ,0 Is the subscript of the first element .
in addition ,Java The array in is itself a reference data type , Its length attribute is length. Arrays can be divided into ： One dimensional array and multidimensional array , Let's start with a one-dimensional array .
<>9.1 One dimensional array
When each element in an array has only one subscript , This kind of array is “ One dimensional array ”. Arrays are reference data types , There are two things to do before using reference data types ： Declaration and initialization .
9.1.1 Array declaration
The declaration of an array declares the element types in the array , Variable name of array .
The syntax of array declaration is as follows ：
Element data type  Array variable name ;
Element data type Array variable name ;
Visible arrays can be declared in two forms ： One is two brackets （） After element data type ; The other is two brackets （） Follow variable name .
An example of array declaration is as follows ：
9.1.2 Array initialization
The array is initialized when the declaration is completed , The process of array initialization is to allocate memory space for each element of the array , And provide initial values for each element . After initialization, the length of the array is determined and cannot be changed