# Thread: What does this program line print out? (tables (or matrices?))

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## What does this program line print out? (tables (or matrices?))

Here's a question that I need to know the answer for. What does this program print out at the end?

As I've understood it, the values mx should get at [0], [1] and [2] are 0, 1 and 4 on both of those.

I've figured a whole lot of ways to calculate sum, for example (0+4+0) + (4+4+1) + (9 + 4+4), but none of those add up.

Java Code:
```int[][] mx = new int[3][3];
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
mx[i][j] = i * j;
}
}
int sum = 0;
for (int i = 0; i < 3; i++) {
sum = sum + mx[2][i];
}
System.out.println(sum);```

So two questions: what number does it produce and why?

Thanks. Your help is very much appreciated.

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## Re: What does this program line print out? (tables (or matrices?))

You have a 3x3 matrix
[x, x, x]
[x, x, x]
[x, x, x]
which is filled by your first loops.
i and j are 0 to 3. so you will fill the first line, than the second and the third. so, for the first line, it will be 0, 0 * everything is 0, so the first line is fully filled with 0
->
[0, 0, 0]
[x, x, x]
[x, x, x]
for the second line, i will be 1, j will be 0,1 and 2.
1*0 = 0
1*1 = 1
1*2 = 2
->
[0, 0, 0]
[0, 1, 2]
[x, x, x]
the last line is yours...you will get it, i`m sure :-)

so, in the loop at the lines 8 - 10, it will sum up only the values from "column" 2
0+2+x = ??

I hope it helps you

3. ## Re: What does this program line print out? (tables (or matrices?))

This sounds like a homework question. Asking us what it does is pretty much defeating the purpose of the assignment, isn't it?

Trace through it with a piece of paper and a pencil. What do you expect to happen?

Then put together a little program that tests that assumption. Did it match? If not, step through it with a debugger to figure out what the difference is.

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## Re: What does this program line print out? (tables (or matrices?))

Thanks eRaaaaa! Got it right, finally.

KevinWorkman, quilty as charged. Tried to figure it out for like 20 minutes until I gave up. Not a big deal really, it was one of a set of 10 questions, each correct answer giving one point. And at this course we can gain a maximum of 1400 or so points. A perfectionist in me though didn't want to leave it hanging :D

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