Java ArrayList.addAll (Collection<? extends E> c)() Method

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

This method is used to append all of the elements in the specified collection to the end of this list. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

Package: java.util

Java Platform: Java SE 8

Syntax:

addAll(Collection<? extends E> c)

Parameters:

Return Value:
true if this list changed as a result of the call.

Return Value Type: boolean

Throws:
NullPointerException - if the specified collection is null

Pictorial presentation of ArrayList.addAll() Method

Example: ArrayList.addAll(Collection<? extends E> c) Method

The following example fills an ArrayList object with the contents of another ArrayList object .

import java.util.*;

public class test {
   public static void main(String[] args) {
      
    // create an empty array list with an initial capacity
    ArrayList<String> color_list = new ArrayList<String>(4);

    // use add() method to add values in the list
    color_list.add("White");
    color_list.add("Black");
    color_list.add("Red");
    color_list.add("White");
	
  	// Print out the colors in the ArrayList
    System.out.println("****Color list****");
	for (int i = 0; i < 4; i++)
      {
         System.out.println(color_list.get(i).toString());
      }

	// create an empty array sample with an initial capacity
    ArrayList<String> sample = new ArrayList<String>(3);  
	sample.add("Yellow");
	sample.add("Red");
    sample.add("White");  
	  
    // Now add sample with color_list
     color_list.addAll(sample);
	
	//New size of the list
	System.out.println("New size of the list is: " + color_list.size()); 
	
	// Print out the colors
    System.out.println("****Color list****");
	for (int i = 0; i < 7; i++)
      {
         System.out.println(color_list.get(i).toString());
      }

	  }
}  
 

Output:

F:\java>javac test.java

F:\java>java test
****Color list****
White
Black
Red
White
New size of the list is: 7
****Color list****
White
Black
Red
White
Yellow
Red
White

Example of Throws: addAll(Collection&? extends E> c) Method

NullPointerException - if the specified collection is null.

Let

(int i = 0; i < 8; i++)

in the above example.

Output:

****Color list****                                     
White                                                  
Black                                                  
Red                                                    
White                                                  
New size of the list is: 7                             
****Color list****                                     
White                                                  
Black                                                  
Red                                                    
White                                                  
Yellow                                                 
Red                                                    
White                                                  
Exception in thread "main" java.lang.IndexOutOfBoundsEx
ception: Index: 7, Size: 7                             
        at java.util.ArrayList.rangeCheck(ArrayList.jav
a:635)                                                 
        at java.util.ArrayList.get(ArrayList.java:411) 
        at test.main(test.java:38)

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