Java: Copy one array list into another

Last update on May 21 2025 12:47:04 (UTC/GMT +8 hours)

9. Copy ArrayList

Write a Java program to copy one array list into another.

Sample Solution:-

Java Code:

import java.util.*;
  public class Exercise9 {
  public static void main(String[] args) {
  List<String> List1 = new ArrayList<String>();
  List1.add("1");
  List1.add("2");
  List1.add("3");
  List1.add("4");
  System.out.println("List1: " + List1);
  List<String> List2 = new ArrayList<String>();
  List2.add("A");
  List2.add("B");
  List2.add("C");
  List2.add("D");
  System.out.println("List2: " + List2);
  // Copy List2 to List1
  Collections.copy(List1, List2);
  System.out.println("Copy List to List2,\nAfter copy:");
  System.out.println("List1: " + List1);
  System.out.println("List2: " + List2);
 }
}

Sample Output:

List1: [1, 2, 3, 4]                                                    
List2: [A, B, C, D]                                                    
Copy List to List2,                                                    
After copy:                                                            
List1: [A, B, C, D]                                                    
List2: [A, B, C, D]

Flowchart:

For more Practice: Solve these Related Problems:

Write a Java program to copy an ArrayList into a new ArrayList using the clone() method and then modify the copy without affecting the original.
Write a Java program to copy one ArrayList into another using addAll() and then sort the new list.
Write a Java program to deep copy an ArrayList of custom objects ensuring changes to the copy do not affect the original.
Write a Java program to copy an ArrayList into a new list using Java streams and collect(), then display both lists.

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Java Code Editor:

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