How to declare array in Java?

You can either use array declaration or array literal (but only when you declare and affect the variable right away, array literals cannot be used for re-assigning an array).

For primitive types:

int[] myIntArray = new int[3];
int[] myIntArray = {1,2,3};
int[] myIntArray = new int[]{1,2,3};

For classes, for example String, it's the same:

String[] myStringArray = new String[3];
String[] myStringArray = {"a","b","c"};
String[] myStringArray = new String[]{"a","b","c"};

• answered 8 years ago
• Gul Hafiz

There are two types of array.

One Dimensional Array

Syntax for default values:

int[] num = new int[5];

Or (less preferred)

int num[] = new int[5];

Syntax with values given (variable/field initialization):

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

Or (less preferred)

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

Note: For convenience int[] num is preferable because it clearly tells that you are talking here about array. Otherwise no difference. Not at all.

Multidimensional array

Declaration

int[][] num = new int[5][2];

Or

int num[][] = new int[5][2];

Or

int[] num[] = new int[5][2];

Initialization

 num[0][0]=1;
 num[0][1]=2;
 num[1][0]=1;
 num[1][1]=2;
 num[2][0]=1;
 num[2][1]=2;
 num[3][0]=1;
 num[3][1]=2;
 num[4][0]=1;
 num[4][1]=2;

Or

 int[][] num={ {1,2}, {1,2}, {1,2}, {1,2}, {1,2} };

Ragged Array (or Non-rectangular Array)

 int[][] num = new int[5][];
 num[0] = new int[1];
 num[1] = new int[5];
 num[2] = new int[2];
 num[3] = new int[3];

So here we are defining columns explicitly.
Another Way:

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

For Accessing:

for (int i=0; i<(num.length); i++ ) {
    for (int j=0;j<num[i].length;j++)
        System.out.println(num[i][j]);
}

Alternatively:

for (int[] a : num) {
  for (int i : a) {
    System.out.println(i);
  }
}

Ragged arrays are multidimensional arrays.
For explanation see multidimensional array detail at the official java tutorials

• answered 8 years ago
• Sunny Solu