Count duplicate elements in ArrayList java

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Java - count duplicates in ArrayList

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Created by:

Evie-Grace-Noble

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In this article, we would like to show you how to count duplicated elements in ArrayList in Java.

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Java - count duplicates in ArrayList
Practical example
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Quick solution:

int occurrences = Collections.frequency(myArrayList, element);

Practical example

In this example, we count the number of duplicated elements in letters ArrayList using Collections.frequency() method.

import java.util.*; public class Example { public static void main(String[] args) { List<String> letters = new ArrayList<>(); letters.add("A"); letters.add("A"); letters.add("A"); letters.add("B"); letters.add("B"); letters.add("C"); int occurrencesA = Collections.frequency(letters, "A"); System.out.println("number of A element occurrences: " + occurrencesA); int occurrencesB = Collections.frequency(letters, "B"); System.out.println("number of B element occurrences: " + occurrencesB); int occurrencesC = Collections.frequency(letters, "C"); System.out.println("number of C element occurrences: " + occurrencesC); } }

Output:

number of A element occurrences: 3 number of B element occurrences: 2 number of C element occurrences: 1