Java ArrayList iterator()

The syntax of the iterator() method is:

 arraylist.iterator()

iterator() Parameters

The iterator() method does not take any parameters.

iterator() Return Values

• returns an iterator to loop through the arraylist elements

Note: The iterator returned by the method is stored in the variable of interface Iterator type.

Example 1: Java 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 in the array list languages.add("Java"); languages.add("Python"); languages.add("JavaScript"); languages.add("Swift"); // Create a variable of Iterator // store the iterator returned by iterator() Iterator<String> iterate = languages.iterator(); System.out.print("ArrayList: "); // loop through ArrayList till it has all elements // Use methods of Iterator to access elements while(iterate.hasNext()){ System.out.print(iterate.next()); System.out.print(", "); } } }

Output

 ArrayList: Java, Python, JavaScript, Swift,

In the above example, we have created an arraylist named languages. Notice the line,

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

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

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

• hasNext: returns true if there is a next element in the arraylist
• next(): returns the next element in the arraylist

Note: We have used the ArrayList add() method to insert elements to the arraylist.

Example 2: Get Index of Each Element of ArrayList Using iterator()

 import java.util.ArrayList; import java.util.Iterator; class Main { public static void main(String[] args){ ArrayList<String> languages = new ArrayList<>(); // Add elements in the array list languages.add("Java"); languages.add("Python"); languages.add("JavaScript"); languages.add("Swift"); // Create a variable of Iterator // store the iterator returned by iterator() Iterator<String> iterate = languages.iterator(); System.out.println("Element: Index"); // loop through ArrayList till it has all elements // Use methods of Iterator to access elements 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

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

Note: We have used the Java ArrayList indexOf() method to access the index number of the element.

The ArrayList also provides a listIterator() method to iterate through list only. To learn more, visit Java ListIterator.