Java Program to Reverse a Collection

In this article, we will understand how to reverse a collection. The Collection is a framework that provides architecture to store and manipulate the group of objects. Java Collections can achieve all the operations that you perform on a data such as searching, sorting, insertion, manipulation, and deletion.

Below is a demonstration of the same −

Suppose our input is −

Input list:[Java, program, is, fun]

The desired output would be −

The list after reversing is:
[fun, is, program, Java]

Algorithm

Step 1 - START
Step 2 - Declare a list namely input_list.
Step 3 - Define the values.
Step 4 - Use the built-in function Collections.reverse() and pass the input_list as parameter to reverse the list.
Step 5 - Display the result
Step 6 - Stop

Example 1

Here, we bind all the operations together under the ‘main’ function.

import java.util.*;
public class Demo {
   public static void main(String[] args){
      List<String> input_list = new ArrayList<String>();
      input_list.add("Java");
      input_list.add("program");
      input_list.add("is");
      input_list.add("fun");
      System.out.println("The list is defined as:" + input_list);
      Collections.reverse(input_list);
      System.out.println("\nThe list after reversing is: \n" + input_list);
   }
}

Output

The list is defined as:[Java, program, is, fun]

The list after reversing is:
[fun, is, program, Java]

Example 2

Here, we encapsulate the operations into functions exhibiting object oriented programming.

import java.util.*;
public class Demo {
   static void reverse_list(List<String> input_list){
      Collections.reverse(input_list);
      System.out.println("\nThe list after reversing is: \n" + input_list);
   }
   public static void main(String[] args){
      List<String> input_list = new ArrayList<String>();
      input_list.add("Java");
      input_list.add("program");
      input_list.add("is");
      input_list.add("fun");
      System.out.println("The list is defined as:" + input_list);
      reverse_list(input_list);
   }
}

Output

The list is defined as:[Java, program, is, fun]

The list after reversing is:
[fun, is, program, Java]