Array declaration and memory allocation

Array declarations look like this:

type[] arrayName;

This tells the compiler that arrayName will be used as the name of an array containing type. However, the actual array is not constructed by this declaration. Often an array is declared and constructed in one statement like this:

type[] arrayName = new type[length];

This tells the compiler that arrayName will be used as the name of an array containing type, and constructs an array object containing length number of slots.

An array is an object, and like any other object in Java is constructed out of main storage as the program is running. The array constructor uses different syntax than most object constructors; type[length] names the type of data in each slot and the number of slots. For example:

int[] list = new int[6];
double[] data = new double[1000];
Student[] school = new Student[1250];

Once an array has been constructed, the number of slots it has does not change.

The size of an array can be defined by using a final value.

final int MAX = 200;
int[] numb = new int[MAX];

When an array is declared, enough memory is allocated to set up the full size of the array.