In this article, we will find something out about array in Java Core. This is a fundamental knowldege that we need to know when working with Java.

Let’s get started.

Table of contents

1D Array

Declaration an array

data_type[] name_variable;
  • data_type: primitive data type such as int, char, Double, byte or object.
  • name_variable: identifier.

For example:

int[] values;
Double[] data;

Allocate memory for an 1D array

values = new int[10];
data = new Double[20];

Once the length of an array is defined, it cannot changed in the program.

The index of an array starts from 0. So, the first element is name_variable[0], and the last element is name_variable[n - 1].

The default initial value of elements of an array is 0 for numeric types and false for boolean.

Initialize an array

int[] values = {1, 2, 3, 4, 5};

Multidimensional Array

Declaration an array

int[][] values;
String[][][] data;

Multidimensional array is an array that contains other arrays.

Multidimensional array

Allocate memory for an nD array

values = new int[2][2];
data = new String[3][4][2];

We can ignore the number of columns

String[][] data = new String[3][];

but to be able to fill it, you will have to initialize each row separately:

String[][] data = new String[2][];
data[0] = new String[3];
data[1] = new String[3];

Initialize an array

int[][] values = {
    {1, 2, 3}, 
    {4, 5, 6}, 

int[][][] test = {
        {1, -2, 3}, 
        {2, 3, 4}
        {-4, -5, 6, 9}, 
        {2, 3}