Java Collections unmodifiableSet() Method

The unmodifiableSet() method of Java Collections class is used to get an unmodifiable view of the specified set.

Syntax

Following is the declaration of unmodifiableSet() method:

Parameter

Parameter	Description	Required/Optional
s	It is the set for which an unmodifiable view is to be returned.	Required

Returns

The unmodifiableSet() method returns an unmodifiable view of the specified set.

Exceptions

Example 1

import java.util.*;
public class CollectionsUnmodifiableSetExample1 {
	public static void main(String[] args) {
		Set<Integer> set = new TreeSet<>();
            Collections.addAll(set, 1,2,3,4,5);
            System.out.println("Initial Set: " + set);
            Set<Integer> set2 = Collections.unmodifiableSet(set);
            System.out.println("Unmodifiable Set: " + set2);
            //Modifying the original set
            set.add(15);
            System.out.println("Unmodifiable Set: " + set2);
	      }
}

Test it Now

Output:

Initial Set: [1, 2, 3, 4, 5]
Unmodifiable Set: [1, 2, 3, 4, 5]
Unmodifiable Set: [1, 2, 3, 4, 5, 15]

Example 2

import java.util.*;
public class CollectionsUnmodifiableSetExample2 {
	public static void main(String[] args) {
		Set<String> set = new TreeSet<>();
            Collections.addAll(set, "Google", "Facebook", "Instagram");
            System.out.println("Initial Set: " + set);
            Set<String> set2 = Collections.unmodifiableSet(set);
            System.out.println("Unmodifiable Set: " + set2);
            //Modifying the original set
            set.add("Twitter");
            System.out.println("Unmodifiable Set: " + set2);
	      }
}

Test it Now

Output:

Initial Set: [Facebook, Google, Instagram]
Unmodifiable Set: [Facebook, Google, Instagram]
Unmodifiable Set: [Facebook, Google, Instagram, Twitter]

Example 3

import java.util.*;
public class CollectionsUnmodifiableSetExample3 {
	public static void main(String[] args) {
		Set<Integer> set = new TreeSet<>();
            Collections.addAll(set, 11, 13, 17);
            System.out.println("Original Set: " + set);
            Set<Integer> set2 = Collections.unmodifiableSet(set);
            set2.add(19);
	      }
}

Test it Now

Output:

Original Set: [11, 13, 17]
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.Collections$UnmodifiableCollection.add(Collections.java:1056)
	at myPackage.CollectionsUnmodifiableSetExample3.main(CollectionsUnmodifiableSetExample3.java:9)

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