Java Collections unmodifiableList() Method

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

Syntax

Following is the declaration of unmodifiableList() method:

Parameter

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

Returns

The unmodifiableList() method returns an unmodifiable view of the specified list.

Exceptions

Example 1

import java.util.*;
public class CollectionsUnmodifiableListExample1 {
    public static void main(String[] args) {
    	  List<String> list = new ArrayList<>();
        Collections.addAll(list, "Google", "Mozila FireFox", "Yahoo");
        List<String> list2 = Collections.unmodifiableList(list);
        System.out.println("Unmodifiable List: " + list2);
        list.add("Safari");
        System.out.print("Unmodifiable List after adding element to the list:");
        System.out.println(list2);
        }
}

Test it Now

Output:

Unmodifiable List: [Google, Mozila FireFox, Yahoo]
Unmodifiable List after adding element to the list:[Google, Mozila FireFox, Yahoo, Safari]

Example 2

import java.util.*;
public class CollectionsUnmodifiableListExample2 {
    public static void main(String[] args) {
    	  List<String> list = new ArrayList<>();
        Collections.addAll(list, "Google", "Mozila FireFox", "Yahoo");
        List<String> list2 = Collections.unmodifiableList(list);
        System.out.println("Unmodifiable List: " + list2);
        list2.add("Safari");       
        }
}

Test it Now

Output:

Unmodifiable List: [Google, Mozila FireFox, Yahoo]
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.Collections$UnmodifiableCollection.add(Collections.java:1056)
	at myPackage.UnmodifiableListExample2.main(UnmodifiableListExample2.java:9)

Example 3

import java.util.*;
public class CollectionsUnmodifiableListExample3 {
    public static void main(String[] args) {
    	 ArrayList<Integer> list = new ArrayList<>();
    	 list.add(10);      
    	 list.add(20);
    	 list.add(30);      
    	 list.add(40);    	    
    	 List<Integer> list2 = Collections.unmodifiableList(list);
    	 System.out.println("Unmodifiable list: " + list2);   	    	        	
    	 list.add(50);
    	 System.out.println("Unmodifiable list after adding (50): "+list);
       }
}

Test it Now

Output:

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

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Java Collections unmodifiableList() Method

Syntax

Parameter

Returns

Exceptions

Example 1

Example 2

Example 3

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