Java printing array with nested loop

Question

I misunderstand something in this for loop. Can someone please clarify?

String[][] artikelTabelle;

    artikelTabelle = new String[2][2]; 

    artikelTabelle[0][0] = "Cow";
    artikelTabelle[0][1] = "Sheep";
    artikelTabelle[1][0] = "Dog";
    artikelTabelle[1][1] = "Lion";


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

At first i and j are 0. Consequently, the array [0][0] (Cow) is printed. But during the second iteration, aren't i and j both 1, because of i++ and j++? Meaning that Lion should be printed? What do I misunderstand here? And since artikelTabelle[0].length has the length 2 - why would it be false to replace it with the number 2?

be vary that the inner loop ( the one with j ) is iterated twice, before i is incremented. — Lino
– Lino, Commented Jul 26, 2017 at 11:38

Eran · Accepted Answer · 2017-07-26 11:38:39Z

5

You have two loops, one outer loop and another inner loop nested inside the outer loop.

This means that for each iteration of the outer loop (before each time i is incremented), the entire inner loop is executed (i.e. j goes from 0 to artikelTabelle[0].length before i is incremented).

Therefore first artikelTabelle[0][0] is printed, followed by artikelTabelle[0][1] (not by artikelTabelle[1][1]). artikelTabelle[1][1] is only printed in the second iteration of the outer loop.

As for whether to use 2 instead of artikelTabelle[0].length, the latter is safer, since you don't have to change a hard-coded 2 if later you change the dimensions of the array.

answered Jul 26, 2017 at 11:38

Eran

395k57 gold badges726 silver badges793 bronze badges

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

2 Comments

NewbieJava Over a year ago

Thanks I think I understand now. But to be sure: At first the inner loop is executed, before it gets incremented. Then artikelTabelle[0][0] is printed. And then the inner loop is executed again with j incremented. j is one and artikelTabelle[0][1] gets printed. Then the inner for loop notices, that if it increments again (to 2) the condition that 2 < 2 won't work. Therefore it goes to the outer loop and increments i. i is now 1. It doesn't go through the inner for loop and prints artikelTabelle[1][0]. Then the inner for loop is executed again and artikelTabelle[1][1] is printed. Is that right?

Eran Over a year ago

@TeachMeSenpai Yes that's right, assuming you meant to write It goes through and not It doesn't go through in the next to last sentence.

Sean Kurian · Accepted Answer · 2017-07-26 11:39:53Z

2

artikelTabelle[0].length is indeed 2.

However, you are misreading the loops. It goes like this:

You start off with i being 0, and j being 0. You print out artikelTabelle[0][0]. Now, we're still in the second for loop. Our condition for termination hasn't been met yet. So i is still 0, and we increment j to 1. Now we print out artikelTabelle[0][1]. Since our condition is now met to terminate the second for loop, we resume our first loop. i is incremented to 1, and we repeat the process. We print out artikelTabelle[1][0] and then artikelTabelle[1][1].

Hopefully I was able to help!

answered Jul 26, 2017 at 11:39

Sean Kurian

293 bronze badges

Comments

Boris van Katwijk · Accepted Answer · 2017-07-26 11:40:19Z

2

The outer for loop will execute whatever is inside it for the amount of times you specified.

The inner code (which is also a for loop here) will thus be executed multiple times.

The variable j is scoped to, and initialized in the outer loop, meaning that when the outer loop starts for the second time, the previous variable no longer exists.

answered Jul 26, 2017 at 11:40

Boris van Katwijk

3,1984 gold badges22 silver badges35 bronze badges

Comments

Sandip Solanki · Accepted Answer · 2017-07-26 12:04:16Z

1

in you code artikelTabelle[0].length = 2 and artikelTabelle.length = 2so for outer i loop increased by 1 than inner j for loop loopind two time like this :

i =0 =>j=0,j=1 ; i =1 =>j=0,j=1 ;

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

edited Jul 26, 2017 at 12:04

answered Jul 26, 2017 at 11:46

Sandip Solanki

7431 gold badge8 silver badges16 bronze badges

Collectives™ on Stack Overflow

Java printing array with nested loop

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related