Java ArrayList iterator() Method

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Description

The Java ArrayList iterator() method returns an iterator over the elements in this list in proper sequence. The iterator is fail-fast means after creation of iterator, any structural modification done to arrayList object without using iterator.add() or remove() method will lead to ConcurrentModificationException.

Declaration

Following is the declaration for java.util.ArrayList.iterator() method

public Iterator<E> iterator()

Parameters

NA

Return Value

This method returns an iterator over the elements in this list in proper sequence.

Exception

NA

Example 1

The following example shows the usage of Java ArrayList iterator(object) method. We're creating a ArrayList of Integers. We're adding couple of Integers to the ArrayList object using add() method calls per element and using iterator(object) method, we're iterating the list and print all the elements.

package com.tutorialspoint;
import java.util.ArrayList;
import java.util.Iterator;
public class ArrayListDemo {
   public static void main(String[] args) {
      
      // create an empty array list 
      ArrayList<Integer> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add(0);
      arrayList.add(1);
      arrayList.add(2);
      arrayList.add(3);
      arrayList.add(4);
      arrayList.add(5);
      arrayList.add(6);	  
      Iterator<Integer> iterator = arrayList.iterator();
      iterator.forEachRemaining(i -> System.out.println(i));
   }
}

Output

Let us compile and run the above program, this will produce the following result −

0
1
2
3
4
5
6

Example 2

The following example shows the usage of Java ArrayList iterator(object) method. We're creating a ArrayList of Strings. We're adding couple of Strings to the ArrayList object using add() method calls per element and using iterator(object) method, we're iterating the list and print all the elements.

package com.tutorialspoint;
import java.util.ArrayList;
import java.util.Iterator;
public class ArrayListDemo {
   public static void main(String[] args) {
      
      // create an empty array list
      ArrayList<String> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add("A");
      arrayList.add("B");
      arrayList.add("C");	  
      Iterator<String> iterator = arrayList.iterator();
      iterator.forEachRemaining(i -> System.out.println(i));
   }
}

Output

Let us compile and run the above program, this will produce the following result −

A
B
C

Example 3

The following example shows the usage of Java ArrayList iterator(object) method. We're creating a ArrayList of Student objects. We're adding couple of Student objects to the ArrayList object using add() method calls per element and using iterator(object) method, we're iterating the list and print all the elements.

package com.tutorialspoint;
import java.util.ArrayList;
import java.util.Iterator;
public class ArrayListDemo {
   public static void main(String[] args) {

      // create an empty arrayList
      ArrayList<Student> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add(new Student(1, "Julie"));
      arrayList.add(new Student(2, "Robert"));
      arrayList.add(new Student(3, "Adam"));
      Iterator<Student> iterator = arrayList.iterator();
      iterator.forEachRemaining(i -> System.out.println(i));    
   }
}
class Student {
   int rollNo;
   String name;
   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }
   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

[ 1, Julie ]
[ 2, Robert ]
[ 3, Adam ]