Identify and count duplicates in array ?

Hi guys I been trying this for almost 5 hours and I'm starting to get frustrated...

So, this is the problem, I have an array:

Code:

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MR = new int[4][4];

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Stored in the array I have 16 numbers from 1 to 20 but some of them maybe repeated, I need to identify which numbers are repeated and how many times.

Let´s say, "Number 3 has been found 4 times"... "Number 1 has been found 2 times"... "Number 9 has been found 0 times"

Here's the full code:

Code:

---

import java.awt.event.*;
import javax.swing.*;

public class arraysum extends JFrame implements ActionListener{
       
        int i,ii;
        int[][] M,M1,MR;
        String arregloR="", arreglo1="", arreglo2="";
       
        public arraysum(){
               
                setLayout(null);
               
                M = new int[4][4];
                M1 = new int[4][4];
                MR = new int[4][4];
               
                for(i=0;i<=3;i++){
                       
                        for(ii=0;ii<=3;ii++){
                               
                                M[i][ii]=1 + (int) (Math.random() * 9);
                                M1[i][ii]=1 + (int) (Math.random() * 9);
                                MR[i][ii]=M[i][ii] + M1[i][ii];
                               
                        }
                       
                }
               
               
        }
               
       
        public static void main(String[]args){
       
                arraysum ventana=new arraysum();
                ventana.setBounds(100,50,600,600);
                ventana.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                ventana.setVisible(true);
                ventana.setResizable(false);
               
        }
}

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Thanks in advance :(handshake):

What I would do, since you know the limitations of the values that can be held in the array, is construct a 1-dimensional array of size 20 (i.e. from 1 to 20, but may want to make it size 21 to avoid confusing indices and numbers). Each value will be initialized to 0. Then, go through every number in your 2-dimensional array and every time you encounter a number, increment the value in that index of the 1-dimensional array. At the end, go through that 1-dimensional array and print out any value over 1.

So, something like...

Code:

---

...

int[] counts = new int[21];

for(int i = 0; i < 4; i++)
{
        for(int j = 0; j < 4; j++)
        {
                counts[ MR[i][j] ]++;
        }
}

for(int i = 1; i < counts.length; i++)
{
        if(counts[i] > 1)
        {
                System.out.println("Number " + i + " found " + counts[i] + " times.");
        }
}

...

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Thanks a lot for your answer dude :(y): (I didn't see it before) :s:

But I finally figured out how to do it... I'll post the code as soon as I finish the whole idea.

Thanks again for answer I appreciate it.