Java.util.ArrayList.addAll() Method

Description

The java.util.ArrayList.addAll(Collection<? extends E> c) method 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. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress(implies that the behavior of this call is undefined if the specified collection is this list, and this list is nonempty).

Declaration

Following is the declaration for java.util.ArrayList.addall(c) method

public boolean addAll(Collection<? extends E> c)

Parameters

• c -- This is the collection containing elements to be added to this list.

Return Value

This method returns true if this list changed as a result of the call.

Exception

• NullPointerException -- If the specified collection is null

Example

The following example shows the usage of java.util.Arraylist.addall(c) method.

package com.tutorialspoint;

import java.util.ArrayList;

public class ArrayListDemo {
  public static void main(String args[]) {

    // create an empty array list1 with an initial capacity
    ArrayList<Integer> arrlist = new ArrayList<Integer>(5);
	
    // use add() method to add elements in the list
    arrlist.add(12);
    arrlist.add(20);
    arrlist.add(45);

    // let us print all the elements available in list1
    System.out.println("Printing list1:");
    for (Integer number : arrlist) {
      System.out.println("Number = " + number);
    }

    // create an empty array list2 with an initial capacity
    ArrayList<Integer> arrlist2 = new ArrayList<Integer>(5);
	
    // use add() method to add elements in list2
    arrlist2.add(25);
    arrlist2.add(30);
    arrlist2.add(31);
    arrlist2.add(35);

    // let us print all the elements available in list2
    System.out.println("Printing list2:");
    for (Integer number : arrlist2) {
      System.out.println("Number = " + number);
    }

    // inserting all elements, list2 will get printed after list1
    arrlist.addAll(arrlist2);
	
    System.out.println("Printing all the elements");
    // let us print all the elements available in list1
    for (Integer number : arrlist) {
       System.out.println("Number = " + number);
    }
  }
}

Let us compile and run the above program, this will produce the following result:

Printing list1:
Number = 12
Number = 20
Number = 45
Printing list2:
Number = 25
Number = 30
Number = 31
Number = 35
Printing all the elements
Number = 12
Number = 20
Number = 45
Number = 25
Number = 30
Number = 31
Number = 35