// Java Program to make Collections Read-Only

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class GFG {

    public static void main(String[] args)
    {
        // List of Integer
        List<Integer> numbers = new ArrayList<>();

        // List have 1 to 10 numbers
        for (int i = 1; i <= 10; i++) {
            numbers.add(i);
        }

        // Iterate on the stream of integers and
        // print them
        numbers.stream().forEach(System.out::print);

        // Now we are adding one more element
        numbers.add(11);

        // Removing element from the list
        numbers.remove(8);

        // Updating List¶
        numbers.set(4, 4);

        System.out.println(
            "\nAfter Performing Some Operations");

        numbers.stream().forEach(System.out::print);

        System.out.println(
            "\nHence By default Collections object is Readable and Writable");

        // Now making Read-Only List
        // Using unmodifiableList() method.
        try {
            numbers = Collections.unmodifiableList(numbers);

            // This line will generate an Exception
            numbers.remove(11);
        }
        catch (UnsupportedOperationException
                   unsupportedOperationException) {
            System.out.println(
                "Exceptions is "
                + unsupportedOperationException);
        }
        finally {
            System.out.println(numbers.get(3));
            System.out.println(
                "Now list is only Read-Only");
        }
    }
}

12345678910
After Performing Some Operations
123446781011
Hence By default Collections object is Readable and Writable
Exceptions is java.lang.UnsupportedOperationException
4
Now list is only Read-Only

// Java Program to make
// Set Interface Object Read-Only

import java.util.Set;
import java.util.HashSet;
import java.util.Collections;

class GFG {

    public static void main(String[] args)
    {
        // Set of Integer
        Set<Integer> numbers = new HashSet<Integer>();

        // Set have 1 to 10 numbers
        for (int i = 1; i <= 5; i++) {
            numbers.add(i);
        }

        // print the integers
        numbers.stream().forEach(System.out::print);

        // Removing element from the list
        numbers.remove(5);

        System.out.println("\nAfter Performing Operation");

        numbers.stream().forEach(System.out::print);

        System.out.println(
            "\nSet is also By Default Readable and Writable");

        // Now making Read-Only Set
        // Using unmodifiableSet() method.
        try {
            numbers = Collections.unmodifiableSet(numbers);

            // This line will generate an Exception
            numbers.remove(4);
        }
        catch (UnsupportedOperationException
                   unsupportedOperationException) {
            System.out.println(
                "Exceptions is "
                + unsupportedOperationException);
        }
        finally {
            System.out.println(numbers.contains(3));
            System.out.println("Now Set is Read-Only");
        }
    }
}

12345
After Performing Operation
1234
Set is also By Default Readable and Writable
Exceptions is java.lang.UnsupportedOperationException
true
Now Set is Read-Only