Java Collections unmodifiableCollection() Method

The unmodifiableCollection() method of Java Collections class is used to get an unmodifiable view of the specified collection. If any attempt occurs to modify the returned collection whether direct or via its iterator, result in an UnsupportedOperationException.

Syntax

Following is the declaration of unmodifiableCollection() method:

public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c)

Parameter

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

Returns

The unmodifiableCollection() method returns an unmodifiable view of the specified collection.

Exceptions

Example 1

import java.util.*;
public class CollectionsUnmodifiableCollectionExample1 {
    public static void main(String[] args) {
    	  Collection<String> c = new ArrayList<>();
        Collections.addAll(c, "Google", "Mozila FireFox", "Yahoo");
        Collection<String> c2 = Collections.unmodifiableCollection(c);
        System.out.println("Unmodifiable Collection: " + c2);
        c.add("Safari");
        System.out.println("Unmodifiable Collection after adding element to the original one:");
        System.out.println(c2);
        }
}

Test it Now

Output:

Unmodifiable Collection: [Google, Mozila FireFox, Yahoo]
Unmodifiable Collection after adding element to the original one:
[Google, Mozila FireFox, Yahoo, Safari]

Example 2

import java.util.*;
public class CollectionsUnmodifiableCollectionExample2 {
    public static void main(String[] args) {
    	  Collection<String> c = new ArrayList<>();
        Collections.addAll(c, "Google", "Mozila FireFox", "Yahoo");
        System.out.println("Initial Collection: "+ c);
        Collection<String> c2 = Collections.unmodifiableCollection(c);       
        c2.add("Safari");      
        }
}

Test it Now

Output:

Initial Collection: [Google, Mozila FireFox, Yahoo]
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.Collections$UnmodifiableCollection.add(Collections.java:1056)
	at myPackage.UnmodifiableCollectionExample2.main(UnmodifiableCollectionExample2.java:9)

Example 3

import java.util.*;
public class CollectionsUnmodifiableCollectionExample3 {
    public static void main(String[] args) {
    	 Collection<Integer> coll = new ArrayList<>();
    	 coll.add(10);      
    	 coll.add(20);
    	 coll.add(30);      
    	 coll.add(40);    	    
    	 Collection<Integer> coll2 = Collections.unmodifiableCollection(coll);
    	 System.out.println("Unmodifiable collection: " + coll2);   	    	     	
    	 coll.add(50);
    	 System.out.print("Unmodifiable collection after adding (50): "+coll);
       }
} 

Test it Now

Output:

Unmodifiable collection: [10, 20, 30, 40]
Unmodifiable collection after adding (50): [10, 20, 30, 40, 50]

Next TopicJava Collections Class

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Java Collections unmodifiableCollection() Method

Syntax

Parameter

Returns

Exceptions

Example 1

Example 2

Example 3

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