Counting an Occurrence in an Array (Java)

Question

I am completely stumped. I took a break for a few hours and I can\'t seem to figure this one out. It\'s upsetting!

I know that I need to check the current element in

Answer 1

import java.util.Scanner;

public class array2 {
    public static void main (String[]args) {
        Scanner input = new Scanner (System.in);
        int [] number = new int [101];
        int c;

        do {

            System.out.println("Enter the integers from 1-100");
            c = input.nextInt();
            number[c]++;

        }while (c != 0);
        for(int i = 0; i < number.length ; i++) {
            if (number[i] !=0) {
                if (number[i] == 1)
                    System.out.println(i + " occurs " + number[i] + " time");
                else
                    System.out.println(i + " occurs " + number[i] + " times "); 

            }
        }
    }
}

Answer 2

You need to sort the order of your numbers in the array. You can use a 'sort()' method, which will organize your numbers from smallest to biggest.

You also need two loops, one to compare against the other. Or in my solution's case, I used a 'while statement' and then a 'for loop'.

I dunno if my method of solving your problem is what you are looking for. Maybe there is a shorter and/or better way to solve this. This is just the way I thought of it. Good luck!

public static int getOccurrences(int[] numbers){

    Array.sort (numbers); //sorts your array in order (i,e; 2, 9, 4, 8... becomes, 2, 4, 8, 9)

    int count = 0;
    int start = 0; 
    int move = 0;

        while(start < numbers.length){
            for (int j = 0; j < numbers.length; j++){
                int currentInt = numbers[start];;
                if (currentInt == numbers[j])
                {
                    count++;
                    move++;
                }
            }
                if(count == 1){
                    return ("Number : " + numbers[start] + " occurs " + count + " time ");
            }   else {
                    return ("Number : " + numbers[start] + " occurs " + count + " times ");
            }
                count = 0;
                start = start + move;
                move = 0;
        }
}

Answer 3

@NYB You're almost right but you have to output the count value and also start it from zero on each element check.

    int count=0,currentInt=0;
    for (int i = 0; i < numbers.length; i++)
    {
    currentInt = numbers[i];
    count=0;

       for (int j = 0; j < numbers.length; j++)
           {
             if (currentInt == numbers[j])
                {
                  count++;
                 }
            }
            System.out.println(count);
      }

@loikkk I tweaked your code a bit for print out of occurrence for each element.

int[] a = { 1, 9, 8, 8, 7, 6, 5, 4, 3, 3, 2, 1 };

    Arrays.sort(a);

    int nbOccurences = 1;

    for (int i = 0, length = a.length; i < length; i++) {
        if (i < length - 1) {
            if (a[i] == a[i + 1]) {
                nbOccurences++;
            }
        } else {
            System.out.println(a[i] + " occurs " + nbOccurences
                    + " time(s)"); //end of array
        }

        if (i < length - 1 && a[i] != a[i + 1]) {
            System.out.println(a[i] + " occurs " + nbOccurences
                    + " time(s)"); //moving to new element in array
            nbOccurences = 1;
        }

    }

Answer 4

We can use java 8 Stream API to create Frequency Map

Stream.of("apple", "orange", "banana", "apple") .collect(Collectors.groupingBy(Function.identity(), Collectors.counting())) .entrySet() .forEach(System.out::println);

The downstream operation is itself a collector (Collectors.counting()) that operates on elements of type String and produces a result of type Long. The result of the collect method call is a Map.

This would produce the following output:

banana=1

orange=1

apple=2

Answer 5

package countoccurenceofnumbers;

import java.util.Scanner;
public class CountOccurenceOfNumbers {


    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int [] num = new int[100]; 
        int [] count = new int[100];
        //Declare counter variable i
        //and temp variable that will
        //temporarily hold the value
        //at a certain index of num[] array
        int i,temp = 0;
        System.out.println("Enter the integers between 1 and 100: ");

        //Initialize num[] array with user input
        for(i=0; i < num.length; i++){
            num[i] = input.nextInt();
            //expected input will end when user enters zero
            if(num[i] == 0){
                break;
            }
        }//end of for loop

        //value at a given index of num array 
        //will be stored in temp variable
        //temp variable will act as an index value
        //for count array and keep track of number
        //of occurences of each number
        for(i = 0; i < num.length; i++){
                temp = num[i];
                count[temp]++;
            }//end of for looop

        for(i=1; i < count.length; i++){

            if(count[i] > 0 && count[i] == 1){
             System.out.printf("%d occurs %d time\n",i, count[i]);
             }
            else if(count[i] >=2){
                System.out.printf("%d occurs %d times\n",i, count[i]);
            }


         }//end of for loop

    }//end of main
    }//end of CountOccurrenceOfNumbers

///////////OUTPUT//////////////////////

Enter the integers between 1 and 100:
2 5 6 5 4 3 23 43 2 0
2 occurs 2 times
3 occurs 1 time
4 occurs 1 time
5 occurs 2 times
6 occurs 1 time
23 occurs 1 time
43 occurs 1 time
BUILD SUCCESSFUL (total time: 3 minutes 23 seconds)

Answer 6

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 // This program counts the number of occurrences of error message. It read the data from Excel sheet for the same.
public class fileopen {
    public static void main(String[] args) {

        String csvFile = "C:\\Users\\2263\\Documents\\My1.csv";
        BufferedReader br = null;
        String line = "";
        String cvsSplitBy = ",";
        List<String> list = new ArrayList<String>();

        String[] country = null;
        Map<String, Integer> hm = new HashMap<String, Integer>();
        try {

            br = new BufferedReader(new FileReader(csvFile));
            while ((line = br.readLine()) != null) {

                // use comma as separator
                country = line.split(cvsSplitBy);

                list.add(country[2]);

                System.out.println(country[1]);
            }
            for (String i : list) {
                Integer j = hm.get(i);
                hm.put(i, (j == null) ? 1 : j + 1);
            }
            // displaying the occurrence of elements in the arraylist
            for (Map.Entry<String, Integer> val : hm.entrySet()) {
                if(val.getKey().equals("Error Message")){
                    System.out.println(val.getKey());
                    continue;
                }
                System.out.println(val.getKey() + " " + val.getValue());
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}