Using a for loop to Print and Two-Dimensional Array in Java

Question

I am trying to complete an assignment (so point in the general direction would help greatly) within which I have to (in order):

Declare a 2d String Array,
Assign Values to the array of two people and their favourite drink
Output using a for loop

public class doublearray {
    public static void main(String[] args){
        String Preferences [] [] = new String [2][2];
        Preferences [0][0]= "Tom, Coke";
        Preferences [1][1]= "John, Pepsi";

        for (int i=0; i<2; i++){
            for (int j =0; j<3; j++){
                System.out.print(Preferences[i][j]);
            }
        }
    }   
}

I receive this error message

Tom, CokenullException in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2 at doublearray.main(doublearray.java:15)

Now, I understand that ",Tom,Coke" have been assigned only to ONE [0] which is why null appears, but I've no idea how to remedy that or make it print successfully.

Any help would be most appreciated, I've been stuck on this for about an hour. Thank ya'll.

The inner loop will allow j to be 2 which is out of the bounds of the inner array. In other words Preferences[0][2] is out of the bounds of the array because the length is 2. Inner loop should be j < 2, not 3. Or more reliably Preference[i].length. — Logan Murphy
– Logan Murphy, Commented Aug 1, 2013 at 14:52
Than you guys very much, I had changed that earlier from >2 to >3 to attempt to rid myself of 'nullnull' being printed. Cheers! :) — Dan Wyer
– Dan Wyer, Commented Aug 1, 2013 at 14:57

Óscar López · Accepted Answer · 2013-08-01 14:52:13Z

11

Try this, it's the correct way to traverse a two-dimensional array of arbitrary size:

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

answered Aug 1, 2013 at 14:52

Óscar López

237k38 gold badges321 silver badges391 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Michael Laffargue · Accepted Answer · 2013-08-01 15:07:34Z

4

You may want something like that :

Preferences [0][0]="Tom";
Preferences [0][1]="Coke";
Preferences [1][0]="John";
Preferences [1][1]="Pepsi";

You'll know that Preferences[0] is about Tom
You'll know that Preferences[1] is about John

And once you have it, the columns will be [0]=>"name" [1] =>"drink"

[0][1] will give you Tom[0] s drink[1] [Coke] for example.  
[0][0] will give you Tom[0] s name[0] [Tom] for example.
[1][1] will give you John[1] s drink[1] [Pepsi] for example.  
[1][0] will give you John[1] s name[0] [John] for example.

edited Aug 1, 2013 at 15:07

answered Aug 1, 2013 at 14:55

Michael Laffargue

10.3k6 gold badges46 silver badges76 bronze badges

Comments

Narendra Pathai · Accepted Answer · 2013-08-01 15:00:08Z

2

for (int i=0; i<2; i++){
  //size for inner loop was 3 but should be 2      
  for (int j =0; j<2; j++){

    System.out.print(Preferences[i][j]);}
}
 }

For arbitrary size

for (int i=0; i<Preferences.length; i++){
      for (int j =0; j<Preferences[i].length; j++){

        System.out.print(Preferences[i][j]);}
    }
     }

edited Aug 1, 2013 at 15:00

answered Aug 1, 2013 at 14:51

Narendra Pathai

42.1k18 gold badges88 silver badges122 bronze badges

Comments

Prabhaker A · Accepted Answer · 2013-08-01 14:51:39Z

1

In second loop j should also j<2 instead of j<3

answered Aug 1, 2013 at 14:51

Prabhaker A

8,5131 gold badge20 silver badges24 bronze badges

Comments

Michael Yaworski · Accepted Answer · 2013-08-01 14:51:45Z

1

for (int j =0; j<3; j++){

needs to be

for (int j =0; j<2; j++){

You didn't make the array big enough for j to be == 2 so it's out of bounds

answered Aug 1, 2013 at 14:51

Michael Yaworski

13.5k19 gold badges72 silver badges98 bronze badges

Comments

Suresh Atta · Accepted Answer · 2013-08-01 14:52:01Z

1

Simple

 for (int i=0; i<2; i++){
        for (int j =0; j<2; j++){

    System.out.print(Preferences[i][j]);}
}

answered Aug 1, 2013 at 14:52

Suresh Atta

122k38 gold badges206 silver badges315 bronze badges

1 Comment

Dan Wyer Over a year ago

Thank you very much, that has ridded me of the error but the return is now Tom,Cokenullnull,John Pepsi,

Juned Ahsan · Accepted Answer · 2013-08-01 14:52:10Z

1

You have defined your 2D array as:

new String [2][2];

and your loop seeems to be tring to fetch the elements such as

new String [0][3]; and so on because of your inner for loop:

    for (int j =0; j<3; j++)

Leading to array index out of bound. You may need to change the inner for loop to

    for (int j =0; j<2; j++)

and try.

answered Aug 1, 2013 at 14:52

Juned Ahsan

68.9k12 gold badges101 silver badges138 bronze badges

Comments

Emmanuel Chukwu · Accepted Answer · 2024-11-24 15:59:23Z

1

Try this.

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

answered Nov 24, 2024 at 15:59

Emmanuel Chukwu

111 bronze badge

Comments

Loki · Accepted Answer · 2013-08-01 14:51:32Z

0

Look at your second for-loop. Consider you only have space for 2 Values per final dimension

answered Aug 1, 2013 at 14:51

Loki

4,1406 gold badges32 silver badges51 bronze badges

Comments

Ilesh Patel · Accepted Answer · 2013-08-01 14:54:15Z

0

How can you take your j from 0 to 2 since your array length is 2 and you start your loop from 0.

change for (int j =0; j<3; j++) to for (int j =0; j<2; j++)

answered Aug 1, 2013 at 14:54

Ilesh Patel

455 bronze badges

Comments

VeryMery · Accepted Answer · 2019-06-06 10:13:14Z

0

    for (String[] row : Preferences) {
        System.out.println (Arrays.toString(row) );
    }

Output:

[Tom, Coke, null]

[null, John, Pepsi]

edited Jun 6, 2019 at 10:13

answered Jun 6, 2019 at 9:58

VeryMery

11 bronze badge

1 Comment

bkis Over a year ago

Welcome to SO! It is always a good idea to provide some explanation along with your answer code. People looking for a solution will more likely understand your answer.

Collectives™ on Stack Overflow

Using a for loop to Print and Two-Dimensional Array in Java

11 Answers 11

Comments

Comments

Comments

Comments

Comments

1 Comment

Comments

Comments

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

11 Answers 11

Comments

Comments

Comments

Comments

Comments

1 Comment

Comments

Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related