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Java - count distinct values in ArrayList
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In this article, we would like to show you how to count distinct values in ArrayList in Java.
Quick solution:
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Set<String> mySet = new HashSet<>(myArrayList);2
System.out.println(distinctSet.size());or
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long unique = myArrayList.stream().distinct().count();
In this example, we create HashSet from the letters ArrayList to remove duplicates. Then we use size() method to get the number of unique values in letters ArrayList.
Practical example:
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import java.util.*;2
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public class Example {4
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public static void main(String[] args) {6
List<String> letters = new ArrayList<>();7
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letters.add("A");9
letters.add("A");10
letters.add("A");11
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letters.add("B");13
letters.add("B");14
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letters.add("C");16
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Set<String> distinctSet = new HashSet<>(letters); // removes duplicates18
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System.out.println("Number of unique values: " + distinctSet.size());20
}21
}Output:
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Number of unique values: 3In this example, we use stream to count distinct values in letters ArrayList.
Note: This solution works only for Java 8 version and higher.
Practical example:
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import java.util.*;2
3
public class Example {4
5
public static void main(String[] args) {6
List<String> letters = new ArrayList<>();7
8
letters.add("A");9
letters.add("A");10
letters.add("A");11
12
letters.add("B");13
letters.add("B");14
15
letters.add("C");16
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long unique = letters.stream()18
.distinct()19
.count();20
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System.out.println("Number of unique values: " + unique);22
}23
}Output:
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Number of unique values: 3