Java generic method: Reverse list elements

Last update on March 13 2025 08:59:55 (UTC/GMT +8 hours)

Write a Java program to create a generic method that takes a list of any type and returns it as a new list with the elements in reverse order.

Sample Solution:

Java Code:

// ReverserList.java
// ReverserList Class
import java.util.ArrayList;
import java.util.List;

public class ReverserList {

  public static < T > List < T > reverseList(List < T > originalList) {
    List < T > reversedList = new ArrayList < > ();

    for (int i = originalList.size() - 1; i >= 0; i--) {
      reversedList.add(originalList.get(i));
    }

    return reversedList;
  }

  public static void main(String[] args) {
    List < Integer > numbers = List.of(1, 2, 3, 4, 5, 6);
    List < String > colors = List.of("Red", "Green", "Orange");

    List < Integer > reversedNumbers = reverseList(numbers);
    System.out.println("Original list of numbers: " + numbers);
    System.out.println("Reversed numbers: " + reversedNumbers); // Output: [6, 5, 4, 3, 2, 1]

    List < String > reversedWords = reverseList(colors);
    System.out.println("\nOriginal list of colors: " + colors);
    System.out.println("Reversed colors: " + reversedWords); // Output: [Orange, Green, Red]
  }
}

Sample Output:

 Original list of numbers: [1, 2, 3, 4, 5, 6]
Reversed numbers: [6, 5, 4, 3, 2, 1]

Original list of colors: [Red, Green, Orange]
Reversed colors: [Orange, Green, Red]

Explanation:

In this program, we define a generic method reverseList() that takes a list originalList as input. The method creates the reversedList from an ArrayList. It iterates over the originalList in reverse order using a for loop and adds each element to the reversedList with the add() method.

The method returns the reversedList at the end.

In the main() method, we demonstrate the reverseList() method by passing a list of integers (numbers) and a list of strings (words). We reverse the elements of each list and print the reversed list.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to create a generic method that reverses a list in place without using additional data structures.
• Write a Java program to create a generic method that returns a new list with the elements in reverse order using recursion.
• Write a Java program to create a generic method that reverses a list and then rotates it by a user-specified offset.
• Write a Java program to create a generic method that produces a reversed deep copy of a list ensuring the original list remains unmodified.

Java Code Editor:

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