Program/Source Code:

The source code to replace an item in the LinkedList collection is given below. The given program is compiled and executed successfully.

// Java program to replace an item in 
// LinkedList collection

import java.util.*;

public class Main {
  public static void main(String[] args) {
    LinkedList < Integer > list = new LinkedList < Integer > ();

    list.add(1);
    list.add(2);
    list.add(3);
    list.add(4);
    list.add(5);

    System.out.println("List items: \n" + list);
    list.set(2, 4);
    list.set(3, 6);

    System.out.println("Updated List: \n" + list);
  }
}

Output:

List items: 
[1, 2, 3, 4, 5]
Updated List: 
[1, 2, 4, 6, 5]

Explanation:

In the above program, we imported the "java.util.LinkedList" package to use the LinkedList collection class. Here, we created a class Main. The Main class contains a main() method. The main() method is the entry point for the program.