Question

Display all the distinct numbers and their frequencies in the array.
Hint: Use a map.

STARTER CODE:

import java.util.HashMap;

public class NumberFrequncies {
   public static void main(String[] args) {
       int[] numbers = {2, 3, 0, 1, -1, 9, 10, 10, 9, 3, 0, 2};
      
       //TODO: ------------
       /* Add code below to store the distinct numbers and their count
       * in a data structure called numberFrequencyMap
       */

      
      
      
       // -------------Your code ends here--------
      
      
       System.out.println("The distinct numbers contained in the array:");
       numberFrequencyMap.forEach(
           (number, count) -> System.out.println(number + " occurs " + count + " time."));
   }
}

Answer 1

Answer:

Explanation:

Array is traversed using for loop and containsKey method is used to check if the number is present in map or not.

If present the value of that key is incremented using get function , otherwise the number is added as key and value is set to 1.

Here is the code:

import java.util.HashMap;

public class Main {
public static void main(String[] args) {
int[] numbers = {2, 3, 0, 1, -1, 9, 10, 10, 9, 3, 0, 2};
  
HashMap<Integer, Integer> numberFrequencyMap = new HashMap<>();

for (int i=0; i<numbers.length; i++)
{
if (numberFrequencyMap.containsKey(numbers[i]))
numberFrequencyMap.put(numbers[i], numberFrequencyMap.get(numbers[i]) + 1);
else
numberFrequencyMap.put(numbers[i], 1);
}
  
System.out.println("The distinct numbers contained in the array:");
numberFrequencyMap.forEach(
(number, count) -> System.out.println(number + " occurs " + count + " time."));
}
}

Output:

The distinct numbers contained in the array: O occurs 2 time. -1 occurs i time. 1 occurs i time. 2 occurs 2 time. 3 occurs 2 time. 9 occurs 2 time. 10 occurs 2 time. ... Program finished with exit code o Press ENTER to exit console.||

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