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Java Collections unmodifiableCollection() Method with Example

Collections Class unmodifiableCollection() method: Here, we are going to learn about the unmodifiableCollection() method of Collections Class with its syntax and example.
Submitted by Preeti Jain, on February 07, 2020

Collections Class unmodifiableCollection() method

• unmodifiableCollection() method is available in java.util package.
• unmodifiableCollection() method is used to get an unmodifiable view of the given collection and when we try to update the given collection then we will get an exception UnsupportedOperationException.
• unmodifiableCollection() method is a static method, it is accessible with the class name and if we try to access the method with the class object then also we will not get any error.
• unmodifiableCollection() method may throw an exception at the time of modifying the given collection.
  UnsupportedOperationException: This exception may throw when we try to modify the given collection.

Syntax:

    public static Collection unmodifiableCollection(Collection co);

Parameter(s):

• Collection co – represents the collection object for which a non-modifiable view is to be retrieved.

Return value:

The return type of this method is Collection, it returns an unmodifiable view of the given collection.

Example:

// Java program to demonstrate the example 
// of Collection unmodifiableCollection()
// method of Collections

import java.util.*;

public class UnmodifiableCollectionOfCollections {
    public static void main(String args[]) {
        // Instatiates an array list object
        List < Integer > arr_l = new ArrayList < Integer > ();

        // By using add() method is to add
        // objects in an array list 
        arr_l.add(10);
        arr_l.add(20);
        arr_l.add(30);
        arr_l.add(40);
        arr_l.add(50);

        // Display ArrayList
        System.out.println("Array List: " + arr_l);

        // By using unmodifiableCollection() method is to
        // represent the array list in an unmodifiable view
        Collection co = Collections.unmodifiableCollection(arr_l);

        // We will get an exception if we 
        // try to add an element in an unmodifiable
        // collection

        /* co.add(60); */
    }
}

Output

Array List: [10, 20, 30, 40, 50]