Adding arrays output

Question

I'd need some help with this. I'm new to java and this is my task:

I have to write code that has an integer array in it. A pair of the arrays values have to be =42. Then I have to output the pair through normal System.out.println.

This is the code I've got so far. Maybe I even got this completely wrong. My problem is getting the program to correctly output what the pairs are that are =42.

public class Main {
    public static void main(String[] args) {
        int[] array = { 2, 3, 5, 6, 8, 6, 5, 39, 40, 34 };
        for (int i = 0; i < array.length; i++) {
            for (int k = 0; k < array.length; k++)
               if (array[i] + array[k] == 42)
                   System.out.println("Found pairs at");
        }
    }
}

Answer 1

You're almost there :) You can build the output string simply by using the + operator:

public class Main {
    public static void main(String[] args) {
        int[] array = {2,3,5,6,8,6,5,39,40,34};

        for (int  i=0; i< array.length  ; i++) {
            for (int k=0; k< array.length; k++) {
                if (array[i] + array[k] == 42)
                    System.out.println("Found pairs at " + i + " " + k + ": " + array[i] + " and " + array[k] + " equals 42");
            }
        }
    }
}

Alternatively, you could use the format function, which is probably easier to read:

System.out.format("Found pairs at %d %d : %d and %d equals 42", i, k, array[i], array[k]);

Answer 2

public static void main (String[] args) throws java.lang.Exception
{
    int[] array = {2,3,5,6,8,6,5,39,40,34};
    for (int i=0; i<array.length; i++){
        for (int k=0; k<array.length; k++)
           if (i != k && array[i] + array[k] == 42)
               System.out.println("Found pairs at " + i + " and " + k + ".");
    }
}

Output:

Found pairs at 0 and 8.
Found pairs at 1 and 7.
Found pairs at 4 and 9.
Found pairs at 7 and 1.
Found pairs at 8 and 0.
Found pairs at 9 and 4.

See a live demo.

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Edit: I have added i!=k in the if condition because you are looking for two numbers in the array that sum to 42. So, if the number 21 appears in the input array, your program will give you the index of number 21 twice when i=k since you are checking array[i] + array[k] == 42.