How are arrays implemented in java?

Question

Arrays are implemented as objects in java right? If so, where could I look at the source code for the array class. I am wondering if the length variable in arrays is defined

Answer 1

We can say that An array is a container that holds a fixed length of data of single data type. eg.

int[] MyArray = new int[101]; // allocates memory for 101 integers, Range from 0 to 100.

and for multidimensional

String[][] names = {{"FirstName", "LastName"},{"Kaji", "Islam"},...};

and for character array

char[] ch={'a','b'....};

Answer 2

For every Array we declare, corresponding classes are there in Java but it's not available to us.You can see the classes by using getClass().getName()

    int[] arr=new int[10];
    System.out.println(arr.getClass().getName());

Output : [I

where "[" represents one dimension array and "I" represents Integer. Similarly, we can have

    [F for one-dimensional float arrays
    [Z for one-dimensional boolean arrays
    [J for one-dimensional long arrays
    [[I for two-dimensional int arrays

and so on.

Answer 3

Although arrays are Objects in the sense that they inherit java.lang.Object, the classes are created dynamically as a special feature of the language. They are not defined in source code.

Consider this array:

MySpecialCustomObject[] array;

There is no such source code for that. You have created it in code dynamically.

The reason why length is in lower case and a field is really about the fact that the later Java coding standards didn't exist at the time this was developed. If an array was being developed today, it would probably be a method: getLength().

Length is a final field defined at object construction, it isn't a constant, so some coding standards would not want that to be in upper case. However in general in Java today everything is generally either done as a constant in upper case or marked private with a public getter method, even if it is final.

Answer 4

Implementing array in Java requires access to memory location or do pointer arithmetic. As Java does not let you to allocate memory, it does the Arrays implementation for you. Java language provides that implementation.