How to demonstrate 2 d matrix in java?

Question

1.00/5 (1 vote)

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The problem is in output showing 1 error that I donot understand ..
Where is error?

What I have tried:

import java.util.*;


 /*Please dont change class name, Dcoder 
 and class must not be public*/

 //Compiler version JDK 1.8
//output of the given matrix is  // 0 1 2 3 4
                                // 5 6 7 8 9
                                  10 11 12 13 14
                                 
 15 16 17 18 19
       
 class Dcoder
 { 
public static void main(String args[])
 { 

int I,j,k=0;

int A[][]=new int[4][];
for(I=0;I<4;I++){
for(j=0;j<5;j++){

A[I][j]= k;

k++;

}}

for(I=0;I<4;I++){
for(j=0;j<5;j++){
System.out.println("" + A[I][j]);

System.out.println(); 
}}
}
}

Posted 23-Apr-18 19:25pm

Deepak pandey

Updated 23-Apr-18 20:01pm

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OriginalGriff · Accepted Answer · 2018-04-23T20:02:00

Look at your code:

Java

int A[][]=new int[4][];
for(I=0;I<4;I++){
for(j=0;j<5;j++){

A[I][j]= k;

k++;

}}

And let's start by making it a little more readable, shall we?

Java

int a[][] = new int[4][];
for(i = 0; i < 4; i++){
    for(j = 0; j < 5; j++){
        a[i][j] = k;
        k++;
    }
}

Be consistent in your variable naming: local variables should be lowercase, not a mixture, and get your indentation correct! It makes your code a whole load easier to read...
You declare the 2D array, but you only specify one size: so the system doesn't allocate any memory for the "second dimension". No memory, and it will fail when you try to access it.
Try this:

int a[][] = new int[4][5];

It should get you a little further.