I don't know why my variables are getting these values

Question

public int Gauss_Jordan(double[][] matrix, int numOfRows, int numOfCols) {
    for (int col_j = 0; col_j<numOfCols; col_j++) {
        row_i = nonzeros ++;
        System.out.println(row_i+" and "+nonzeros);
    }
    //return matrix;

    return 0;
}

up above in the method called "Gauss_Jordan", you can see a for loop where it iterates until a certain condition is met. (duh.. lol sorry).

so i set row_i = nonzeros++ but here's the thing, when I print out each iteration i get

0 and 1,
1 and 2,
2 and 3

. I would expect the output to be:

1 and 1,
2 and 2,
3 and 3.

How come this is not the case?

http://stackoverflow.com/questions/5413548/java-prefix-postfix-of-increment-decrement-operators-need-help-with-example — zw324, May 15 '13 at 14:36

score 4 · Answer 1 · answered May 15 '13 at 14:37

4

You'd need ++nonzeros instead of nonzeros++ to get what you expect.

answered May 15 '13 at 14:37

Bruno Lowagie

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@HovercraftFullOfEels ... Pretty sure he was ..... what's the issue? – rolfl May 15 '13 at 14:38
1

time to drink more coffee. that's the issue. sorry. – Hovercraft Full Of Eels May 15 '13 at 14:40
1

@HovercraftFullOfEels go back to the java tutorial .... ;-) http://docs.oracle.com/javase/tutorial/java/nutsandbolts/op1.html – rolfl May 15 '13 at 14:41
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@rolfl: my eyes weren't seeing things clearly. 1+ to bruno and sanbhat. – Hovercraft Full Of Eels May 15 '13 at 14:51
+1 from me on the coffee ;-) – Bruno Lowagie May 15 '13 at 14:52

score 4 · Answer 2 · answered May 15 '13 at 14:37

4

Thats called post-increment;

When you say row_i = nonzeros ++;

first the row_i will get assigned with the value of nonzeros and the nonzero will get incremented.

try pre-increment

row_i = ++nonzeros;

answered May 15 '13 at 14:37

sanbhat

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score 0 · Answer 3 · answered May 15 '13 at 14:39

0

If pre-increment is not what you wanted. Check the initialization of nonzeros and change it into '1` for it to show up as you want. Your codes are functioning as they should.

answered May 15 '13 at 14:39

Starx

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I don't know why my variables are getting these values

3 Answers3