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Two-dimensional arrays

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In this section, you will learn about two-dimensional arrays with an example.`

Two-Dimensional Arrays

     

Two-dimensional arrays are defined as "an array of arrays". Since an array type is a first-class Java type, we can have an array of ints, an array of Strings, or an array of Objects. For example, an array of ints will have the type int[]. Similarly we can have int[][], which represents an "array of arrays of  ints". Such an array is said to be a two-dimensional array. 
The command

  int[][] A = new int[3][4];

declares a variable, A, of type int[][], and it initializes that variable to refer to a newly created object. That object is an array of arrays of ints. Here, the notation int[3][4] indicates that there are 3 arrays of ints in the array A, and that there are 4 ints in each of those arrays.
To process a two-dimensional array, we use nested for loops. We already know about for loop. A loop in a loop is called a Nested loop. That means we can run another loop in a loop. 

Notice in the following example how the rows are handled as separate objects. 

Code: Java
int[][] a2 = new int[10][5];
 // print array in rectangular form
 for (int i=0; i<a2.length; i++) {
     for (int j=0; j<a2[i].length; j++) {
         System.out.print(" " + a2[i][j]);
     }
     System.out.println("");
 }

In this example, "int[][] a2 = new int[10][5];" notation shows a two-dimensional array. It declares a variable a2 of type int[][],and it initializes that variable to refer to a newly created object. The notation int[10][5] indicates that there are 10 arrays of ints in the array a2, and that there are 5 ints in each of those arrays. 

Here is the complete code of the example:

public class twoDimension{
  public static void main(String[] args) {
  int[][] a2 = new int[10][5];
  for (int i=0; i<a2.length; i++) {
  for (int j=0; j<a2[i].length; j++) {
  a2[i][j= i;
  System.out.print(" " + a2[i][j]);
  }
  System.out.println("");
  }
  }
}

Here is the output for the program:

C:\tamana>javac twoDimension.java
C:\tamana>java twoDimension
 0 0 0 0 0
 1 1 1 1 1
 2 2 2 2 2
 3 3 3 3 3
 4 4 4 4 4
 5 5 5 5 5
 6 6 6 6 6
 7 7 7 7 7
 8 8 8 8 8
 9 9 9 9 9
C:\tamana>_

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Posted on: May 28, 2007

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Comments:11
CTRUTH
November 13, 2011
ARRAY IN AN ARRAY

can a program have an array inside an array and in what cases, and what is the limit of arrays one can have ?
shahzad ahmad
December 1, 2011
array

i am loking forward to .............. i like this... plz teach me java
sekhar
December 17, 2011
java with arrays

what is the syntax for addition of two matrix in java with arry's.
abhinav
January 17, 2012
this fucking concept is is not too sexy

please ellaborate it..
ritu
April 15, 2012
java

how we eisaly understand the syntax of the two dimension array?
Remya
August 24, 2012
java program

How to randomly place the string array in the multidimentional array in java?
priti pandey
September 4, 2012
java

plz give me all available progs of 2d arrays,,and other programs
Teketel petros
April 16, 2013
Java

I like it!
yuvaraj
August 21, 2013
java

how to get an input from the user for an 2D array instead of declearing it before
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