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Java - how to use Iterator with ArrayList

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In this article, we would like to show you how to use iterator with ArrayList in Java.

Quick solution:

Iterator<String> myIterator = myArrayList.iterator();

while (myIterator.hasNext()) {
    System.out.print(myIterator.next() + " ");
}

 

Introduction

Iterator is an object that can be used to loop through collections. In this article, we will focus on the ArrayList collection and loop through it.

Create iterator

To use Iterator, the first thing we need to do is obtain it from a Collection. To do so, we use iterator() method in the following way:

List<String> myArrayList = ...
Iterator<String> myIterator = myArrayList.iterator();

Iterator methods

  • hasNext() - checks if there is at least one element left to iterate over, it's commonly used as a condition in while loops.
  • next() - steps over the next element and obtains it.

Practical example

In this example, we create an iterator for letters ArrayList to display all the elements in the proper order.

import java.util.*;

public class Example {

    public static void main(String[] args) {
        List<String> letters = new ArrayList<>();

        letters.add("A");
        letters.add("B");
        letters.add("C");

        // create an iterator
        Iterator<String> myIterator = letters.iterator();

        // display values after iterating through the ArrayList
        System.out.println("The iterator values of the list are: ");
        while (myIterator.hasNext()) {
            System.out.print(myIterator.next() + " ");
        }
    }
}

Output:

The iterator values of the list are: 
A B C 

Java Collections - ArrayList

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