How do I insert all elements from one list into another in Java?

Solution

We can add all elements of one list into another list easily using its addAll() method.

Syntax

boolean addAll(Collection<? extends E> c)

Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator.

Type Parameter

• E  − The runtime type of the collection passed.

Parameters

• c  − Collection containing elements to be added to this list.

Returns

True if this list changed as a result of the call

Throws

• UnsupportedOperationException − If the addAll operation is not supported by this list.

• ClassCastException − If the class of an element of the specified collection prevents it from being added to this list.

• NullPointerException − If the specified collection contains one or more null elements and this list does not permit null elements, or if the specified collection is null.

• IllegalArgumentException − If some property of an element of the specified collection prevents it from being added to this list.

Example

The following example shows how to add all elements from a list into another list using the addAll() method.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.List;

public class CollectionsDemo {
   public static void main(String[] args) {
      // Create a list object
      List<Integer> list = new ArrayList<>();

      // add elements to the list
      list.add(1);
      list.add(2);
      list.add(3);
      list.add(4);
      list.add(5);
      list.add(6);

      // print the list
      System.out.println(list);
      List<Integer> list1 = new ArrayList<>();
      list1.add(0);
      list1.addAll(list);
      System.out.println(list1);
   }
}

Output

This will produce the following result −

[1, 2, 3, 4, 5, 6]
[0, 1, 2, 3, 4, 5, 6]