Java Collections reverse()

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In this guide, you will learn about the Collections reverse() method in Java programming and how to use it with an example.

1. Collections reverse() Method Overview

Definition:

The reverse() method of the Collections class in Java is used to reverse the order of elements in a specified list.

Syntax:

Collections.reverse(List<?> list)

Parameters:

list: The list whose elements are to be reversed.

Key Points:

- After executing the method, the list provided will be modified such that the order of its elements is reversed.

- It throws UnsupportedOperationException if the specified list or its list-iterator doesn't support the set operation.

- This is a very efficient method to reverse a list as it doesn't involve any copying of elements.

2. Collections reverse() Method Example

import java.util.*;

public class CollectionsReverseExample {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));

        // Reversing the list
        Collections.reverse(numbers);
        System.out.println("Reversed list: " + numbers);
    }
}

Output:

Reversed list: [5, 4, 3, 2, 1]

Explanation:

In the provided example, we create a list of integers from 1 to 5. We then use the reverse() method to reverse the order of its elements and print the reversed list.

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