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Initialize HashSet in Java
A set is a collection which does not allows duplicate values. HashSet is an implementation of a Set. Following are the ways in which we can initialize a HashSet in Java.
Using constructor − Pass a collection to Constructor to initialize an HashSet.
Using addAll() − Pass a collection to Collections.addAll() to initialize an HashSet.
Using unmodifiableSet() − Pass a collection to Collections.unmodifiableSet() to get a unmodifiable Set.
Using add() − Using add(element) method of Set.
Following is an example of using above ways.
Example
Infinity
Now consider the following code snippet.
Example
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
public class Tester{
public static void main(String[] args) {
List<Integer> list = Arrays.asList(1,2,3,4,5,6);
//Scenario 1
Set<Integer> set1 = new HashSet<>(list);
System.out.println(set1);
//Scenario 2
Set<Integer> set2 = new HashSet<>(list);
Collections.addAll(set2, 1,2,3,4,5,6);
System.out.println(set2);
//Scenario 3
Set<Integer> set3 = Collections.unmodifiableSet(set2);
System.out.println(set3);
//Scenario 4
Set<Integer> set4 = new HashSet<>();
set4.add(1);set4.add(2);set4.add(3);
set4.add(4);set4.add(5);set4.add(6);
System.out.println(set4);
}
}Output
[1, 2, 3, 4, 5, 6] [1, 2, 3, 4, 5, 6] [1, 2, 3, 4, 5, 6] [1, 2, 3, 4, 5, 6]
Updated on: 23-Jun-2020
10K+ Views
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