The syntax of the iterator()
method is:
arraylist.iterator()
iterator() Parameters
The iterator()
method does not take any parameters.
iterator() Return Values
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.