How to output an element that has occured or listed multiple times in an array list from a user input

Question

How to output an element (content of index) that has been repeated by the user input multiple times with out using the collections, hashmap or treemap method?

I am looking for a linear or you could say a mathematical approach rather than a ready command approach, could someone help please?

import java.util.ArrayList;
import java.util.Scanner;
 

Scanner scanner = new Scanner(System.in);
    ArrayList<Integer> arrayList = new ArrayList<>();

    while (true) {
        int input = scanner.nextInt();
        if (input == -1) {
            break;
        }
        arrayList.add(input);
    }
    System.out.println("search for? ");
    for (int loopValue = 0; loopValue < arrayList.size(); loopValue++) {

        int input2 = scanner.nextInt();
        System.out.println(input2 + " is at index " + arrayList.indexOf(input2));
    }

/ a sample output should look similar to the following:

input user:
10
20
20
30
30
40
50
if -1 is inputted, the user will exit the loop

Number you are searching for in an array list?: the user again input the desired number 30

number 30 is at index 3
number 30 is at index 4

how can I show the indices of a frequent number just like above^?

Answer 1

If I understand your question correctly you could do:

System.out.println("search for? ");
int input2 = scanner.nextInt();
for(int i =0; i<arrayList.size();i++){
    if(arrayList.get(i)==input2){
            System.out.println(input2 + " is at index " + i); //e.g. 30 is at index 3
    }
}