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How to loop ArrayList in Java

By Chaitanya Singh | Filed Under: Java Collections

Earlier we shared ArrayList example and how to initialize ArrayList in Java. In this post we are sharing how to iterate (loop) ArrayList in Java.

There are four ways to loop ArrayList:

  1. For Loop
  2. Advanced for loop
  3. While Loop
  4. Iterator

Lets have a look at the below example – I have used all of the mentioned methods for iterating list.

import java.util.*;
public class LoopExample {
   public static void main(String[] args) {

      ArrayList<Integer> arrlist = new ArrayList<Integer>();
      arrlist.add(14);
      arrlist.add(7);
      arrlist.add(39);
      arrlist.add(40);

      /* For Loop for iterating ArrayList */
      System.out.println("For Loop");
      for (int counter = 0; counter < arrlist.size(); counter++) { 		      
          System.out.println(arrlist.get(counter)); 		
      }   		

      /* Advanced For Loop*/ 		
      System.out.println("Advanced For Loop"); 		
      for (Integer num : arrlist) { 		      
           System.out.println(num); 		
      }

      /* While Loop for iterating ArrayList*/ 		
      System.out.println("While Loop"); 		
      int count = 0; 		
      while (arrlist.size() > count) {
	 System.out.println(arrlist.get(count));
         count++;
      }

      /*Looping Array List using Iterator*/
      System.out.println("Iterator");
      Iterator iter = arrlist.iterator();
      while (iter.hasNext()) {
         System.out.println(iter.next());
      }
   }
}

Output:

For Loop
14
7
39
40
Advanced For Loop
14
7
39
40
While Loop
14
7
39
40
Iterator
14
7
39
40

In the comment section below, Govardhan asked a question: He asked, how to iterate an ArrayList using Enumeration. Govardhan here is the code:

How to iterate arraylist elements using Enumeration interface

import java.util.Enumeration;
import java.util.ArrayList;
import java.util.Collections;
 
public class EnumExample {
 
   public static void main(String[] args) {
      //create an ArrayList object
      ArrayList<String> arrayList = new ArrayList<String>();
 
      //Add elements to ArrayList
      arrayList.add("C");
      arrayList.add("C++");
      arrayList.add("Java");
      arrayList.add("DotNet");
      arrayList.add("Perl");
 
      // Get the Enumeration object
      Enumeration<String> e = Collections.enumeration(arrayList);
 
      // Enumerate through the ArrayList elements
      System.out.println("ArrayList elements: ");
      while(e.hasMoreElements())
      System.out.println(e.nextElement());
   }
}

Output:

ArrayList elements: 
C
C++
Java
DotNet
Perl

Comments

  1. Govardhan says

    November 16, 2014 at 5:42 AM

    sir how to iterate arraylist elements using Enumeration interface

    Reply
    • Chaitanya Singh says

      November 18, 2014 at 4:48 AM

      Hi Govardhan,

      I have updated the post and added the code. You can find your answer above in the post. Let me know if you have any further question.

      Reply
      • Govardhan says

        December 5, 2014 at 3:14 PM

        sir I have one more question:=
        1.How to find middle value of a linked list by single pass

        Reply
        • srinath says

          December 20, 2014 at 2:35 AM

          Use two variable, lets call them fastVariable and slowVariable.

          Move the fastVariable twice the speed of slowVariable.

          By the time fastVariable reach end of the list slowVariable will be at middle of the list.

          Thanks.

          Reply
  2. David tolu says

    November 30, 2014 at 7:25 PM

    how to detect duplicate values in an arrayList?

    Reply
  3. Melly says

    April 16, 2018 at 1:14 AM

    Hello!

    So I have two seperate arraylists. I am trying to display both of them on a form, but only one of them is showing up. Is it possible to loop to arrayLists and display them at the same time?

    Reply
    • Chaitanya Singh says

      April 19, 2018 at 12:05 PM

      Melly, You can join both the arraylists and then loop the combined arraylist to display all the elements. Refer this: How to join ArrayList?

      Reply

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