How to get the common values in an array (Java)?

Question

I want to get the common values of list1 and compare it to list2. I got an output of 11121 instead of 121. How can I resolve this?

Here's my code:

public class TwoLists {

    static void arrs() {
        int[] list1 = {1, 6, 2, 1, 4, 1, 2, 1, 8};
        int[] list2 = {1, 2, 1};
    
        for(int i = 0; i < list1.length-1; i++)
        {
            for(int o = i+3; o < list1.length; o++)
            {
                for(int out1 = list1[i]; out1 == list1[o]; out1++)
                {
                    System.out.print(out1);
                    }
                }
            }
        }


    public static void main(String[] args)
    {
        arrs();
    }

}

I do not understand what you want to do. Maybe add some expected input and output? Also, list2 is never used in your code, is this correct? — andrbrue, Oct 02 '20 at 23:22
Does this answer your question? [finding common elements in two integer arrays java](https://stackoverflow.com/questions/40632887/finding-common-elements-in-two-integer-arrays-java) — Spectric, Oct 02 '20 at 23:25

score 0 · Accepted Answer · answered Oct 02 '20 at 23:29

Try the following:

Use a Set<Integer> to record those already found.
then use a nested array going from start to finish for each array
in the outer loop, see if set.contains() the current value.
if so, continue outer loop.
otherwise, compare inner and outer list values.
when a match is found, print it, add to the set, and then break out of the inner loop.
continue next value in outer loop.

There are other, faster ways using just sets exclusively but this would serve as a start.

How to get the common values in an array (Java)?

1 Answers1