Find same object in two arraylist [duplicate]

Question

List A={2,3,3} List B={2,3,5}

I want to get only {2,3} to do the gcd

I tried to use retainall() but result is {2,3,3}

public static int gcd(ArrayList<Integer> A,ArrayList<Integer> B)
{ //A={2,3,3},B={2,3,5}
    A.retainAll(B);
    System.out.println(A);
}

You haven't specified the task clearly enough, that multiple occurrences in both lists are essential, e.g. from {2,3,3,5} and {3,3,7} you expect {3,3}. So, you're getting answers that are correct, but won't help you. — Ralf Kleberhoff
– Ralf Kleberhoff, Commented Mar 14, 2022 at 8:53

Remo · Accepted Answer · 2022-03-14 08:45:24Z

2

I suggest to make use of Set, e.g. HashSet.

https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/util/HashSet.html

In a set, there are no duplicate values.

Set<Integer> set = new HashSet<Integer>(A.retainAll(B));

Also, method params use lowerCase naming.

answered Mar 14, 2022 at 8:45

Remo

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2 Comments

Ralf Kleberhoff Over a year ago

For the greatest common divisor (mentioned as a side-note by the OP), multiple occurrences are essential. So, the Set approach won't work.

Remo Over a year ago

Thx, for pointing out, I am aware of this. Out of the question (well there is not even a clear one), I only got that the author needed a distinct result out of 2 Array lists.

Derrick · Accepted Answer · 2022-03-14 09:19:26Z

0

you can use contains(Object o) method. Returns true if this list contains the specified element. ArrayList

edited Mar 14, 2022 at 9:19

Derrick

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answered Mar 14, 2022 at 8:49

Kaan Baytan

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