Equal values in a list java

Question

As I can do to get to see the result of two or more identical numbers contained in a list. Everything has to be based on lists, the code itself is simple but I have no idea how to achieve the same values print screen.

All this is done under 5 numbers entered in a list.

example:

Introduce 1 - 2 - 3 - 3 - 4

And the output would be the number 3 is repeated.

This is my code:

package generarlista;
import java.util.*;

public class GenerarLista {
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        int num;
        Scanner read = new Scanner (System.in);
        List<Integer> lista = new ArrayList<>();
        System.out.println("A list of 5 integers is generated and printed equal values\n");
        for (int i=1; i<6; i++){
            System.out.println("Enter the value "+ i +" element to populate the list");
            num = read.nextInt();
            lista.add(num);
        }
        System.out.println("Data were loaded \n");
        System.out.println("Values in the list are: ");

        Iterator<Integer> nameIterator = lista.iterator();

        while(nameIterator.hasNext()){
            int item = nameIterator.next();
            System.out.print(item+" / ");
        }
        System.out.println("\n");
        System.out.println("Equals are: ");

    }

}

thank you very much!

Answer 1

There are many different approaches that could solve this problem. This first thing that came to mind for me is to sort the ArrayList and check adjacent characters.

package generarlista;
import java.util.*;

public class GenerarLista {
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    int num;
    Scanner read = new Scanner (System.in);
    List<Integer> lista = new ArrayList<>();
    System.out.println("A list of 5 integers is generated and printed equal values\n");
    for (int i=1; i<6; i++){
        System.out.println("Enter the value "+ i +" element to populate the list");
        num = read.nextInt();
        lista.add(num);
    }
    System.out.println("Data were loaded \n");
    System.out.println("Values in the list are: ");

    Collections.sort(lista);

    List<Integer> duplicates = new ArrayList<>();

    for (int i = 0; i < lista.size(); i++) {
        System.out.print(lista.get(i) + " ");
        if (i < lista.size()-1 && lista.get(i) == lista.get(i+1))
            if (!duplicates.contains(lista.get(i))
                duplicates.add(lista.get(i));
    }      

    System.out.println("\n");
    System.out.println("Equals are: ");

    for (int i = 0; i < duplicates.size(); i++) {
        System.out.print(duplicates.get(i) + " ");
    }

}

}