Java Program to find the frequency of each element in the array
Java Program to find the frequency of each element in the array
Java Program to find the frequency of each element in the array
Program
You can use a loop and a HashMap to find the frequency of each element in an array in Java. A HashMap is a data structure that stores key-value pairs, and it's commonly used for tasks like counting occurrences of elements in a collection. Here's an example of how you could use a HashMap to find the frequency of each element in an array:
import java.util.HashMap;
public class FrequencyCounter
{
public static void main(String[] args)
{
int[] array = {1, 2, 3, 2, 3, 1, 3};
HashMap<Integer, Integer> frequencyMap = new HashMap<>();
// count the frequency of each element in the array
for (int i : array)
{
if (frequencyMap.containsKey(i))
{
frequencyMap.put(i, frequencyMap.get(i) + 1);
}
else
{
frequencyMap.put(i, 1);
}
}
// print out the frequency of each element
for (int key : frequencyMap.keySet())
{
System.out.println("Element " + key + " occurs " + frequencyMap.get(key) + " times.");
}
}
}
In this example, the program initializes an integer array with the values {1, 2, 3, 2, 3, 1, 3} and creates an empty HashMap called frequencyMap. The for loop iterates over the elements of the array and checks if each element is already a key in the HashMap. If it is, the program increases the value associated with that key by one. If it isn't, the program adds a new key-value pair to the HashMap with the element as the key and the value 1.
The second for loop iterates over the keys in the HashMap and prints out the frequency of each element in the format "Element X occurs Y times."
It's a simple but efficient way to count element frequency, as HashMap has O(1) complexity for put, get and containsKey operations.
Also, you can use a similar approach using array instead of HashMap to store the frequency, But It will not be as efficient as using HashMap as searching an element in an array has a O(n) complexity.
Output:
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