[FIXED] Checking common element between two similar Lists using Streams

Issue

Let's say, I've 2 similar lists (not same though). For Example: One List of Integers and another List of Hex String (which can be mapped to Integer), how can I find if there's any common element at same index in both the lists using streams?

Let's consider the following code:

List<Integer> l1 = List.of(11, 12, 13, 14, 15);
List<String> l2 = List.of("F", "E", "D", "C", "B")

boolean isCommon = checkIfCommonElementExists(l1, l2);
System.out.print("There's at least one common element at same index: " + isCommon);

In this example, the 3rd element of both the lists are same i.e 13 or OxD

How can I check (or find) if there's any such common element at same index and break at first match (something like anyMatch()) using Streams? This is a simple problem to solve without streams, but can it be solved using Streams?

Solution

You could do something like below to check if any common elements exist

private static boolean checkIfCommonElementExists(List<Integer> list1, List<String> list2) {
    return IntStream.range(0, Math.min(list1.size(), list2.size()))
            .anyMatch(i -> list1.get(i).equals(Integer.parseInt(list2.get(i),16)));
}

or something like below to get the indices of common elemnts

private static int[] findCommonElementIndexes(List<Integer> list1, List<String> list2) {
    return IntStream.range(0, Math.min(list1.size(), list2.size()))
            .filter(i -> list1.get(i).equals(Integer.parseInt(list2.get(i),16)))
            .toArray();
}

for the given example:

List<Integer> l1 = List.of(11, 12, 13, 14, 15);
List<String> l2 = List.of("F", "E", "D", "C", "B");

boolean isCommon = checkIfCommonElementExists(l1, l2);
System.out.println("There's at least one common element at same index: " + isCommon);

System.out.println("Common indices" + Arrays.toString(findCommonElementIndexes(l1,l2)));

output:

There's at least one common element at same index: true
Common indices: [2]

Answered By - Eritrean
Answer Checked By - Clifford M. (JavaFixing Volunteer)