Usage and examples of Java ArrayList iterator()

Java ArrayList Methods

The Java ArrayList iterator() method returns an iterator to access each element of the array list in the correct order.

The syntax of the iterator() method is:

arraylist.iterator()

iterator() parameters

The iterator() method does not take any parameters.

The return value of iterator()

• Returns an iterator to traverse the elements of the arraylist

NoteThe iterator returned by this method is stored in an interface Iterator type variable.

Example1Java ArrayList iterator()

import java.util.ArrayList;
import java.util.Iterator;
class Main {
　　public static void main(String[] args){
　　　　ArrayList<String> languages = new ArrayList<>();
　　　　//Add elements to the array list
　　　　languages.add("Java");
　　　　languages.add("Python");
　　　　languages.add("JavaScript");
　　　　languages.add("Swift");
　　　　//Create an Iterator variable
　　　　//Store the iterator returned by iterator()
　　　　Iterator<String> iterate = languages.iterator();
　　　　System.out.print("ArrayList: ");
　　　　//Traverse the ArrayList until it contains all elements
　　　　//Access elements using Iterator methods
　　　　while(iterate.hasNext()){
　　　　　　System.out.print(iterate.next());
　　　　　　System.out.print(", ");
　　　　}
　　}
}

Output Result

ArrayList: Java, Python, JavaScript, Swift,

In the above example, we created an array list named languages. Note this line,

Iterator<String> iterate = languages.iterator();

Here, we created a variable named iterate of the Iterator interface. This variable stores the iterator returned by the iterator() method.

Using iterate, we can access the elements of the arraylist.

• hasNextReturns true if there is a next element in the arraylist

• next()Returns the next element in the arraylist

Note: We have usedArrayList add()The method inserts elements into the arraylist.

Example2Use iterator() to get the index of each element in the ArrayList

import java.util.ArrayList;
import java.util.Iterator;
class Main {
　　public static void main(String[] args){
　　　　ArrayList<String> languages = new ArrayList<>();
　　　　//Add elements to the array list
　　　　languages.add("Java");
　　　　languages.add("Python");
　　　　languages.add("JavaScript");
　　　　languages.add("Swift");
　　　　//Create an Iterator variable
　　　　//Store the iterator returned by iterator()
　　　　Iterator<String> iterate = languages.iterator();
　　　　System.out.println("Element: Index");
　　　　//Traverse the ArrayList until it contains all elements
　　　　//Access elements using Iterator methods
　　　　while(iterate.hasNext()){
　　　　　　//Access element
　　　　　　String element = iterate.next();
　　　　　　System.out.print(element　+　:　");
　　　　　　//Access index of each element
　　　　　　System.out.println(languages.indexOf(element));
　　　　}
　　}
}

Output Result

Element:　Index
Java:　0
Python:　1
JavaScript:　2
Swift:　3

Note: We have usedJava ArrayList indexOf()Method to access the index number of the element.

ArrayList also provides the listIterator() method to traverse the list only. For more information, please visitJava ListIterator.

Java ArrayList Methods