Java - Deque iterator() Method

The Java Deque iterator() method returns an iterator over the elements in this deque. This iterator then can be used to iterate each element of the Deque object.

Declaration

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

public Iterator<E> iterator()

Parameters

NA

Return Value

This method returns an iterator over the elements in this deque.

Exception

NA

Example 1

The following example shows the usage of Java Deque iterator() method to iterate Integers. We're adding couple of Integers to the Deque object using add() method calls per element and then iterate and print each element to show the elements added.

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;

public class DequeDemo {
   public static void main(String[] args) {
      
      // create an empty deque
      Deque<Integer> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(15);
      deque.add(22);
      deque.add(25);
      deque.add(20);

      // iterator() is used to print all the elements
      // next() returns the next element on each iteration
      System.out.println("printing elements using iterator:");
      for(Iterator<Integer> itr = deque.iterator();itr.hasNext();)  {
         System.out.println(itr.next());
      }
   }
}   

Output

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

printing elements using iterator:
15
22
25
20

Example 2

The following example shows the usage of Java Deque iterator() method to iterate Strings. We're adding couple of Strings to the Deque object using add() method calls per element and then iterate and print each element to show the elements added.

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;

public class DequeDemo {
   public static void main(String[] args) {
      
      // create an empty deque
      Deque<String> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add("A");
      deque.add("B");
      deque.add("C");
      deque.add("D");

      // iterator() is used to print all the elements
      // next() returns the next element on each iteration
      System.out.println("printing elements using iterator:");
      for(Iterator<String> itr = deque.iterator();itr.hasNext();)  {
         System.out.println(itr.next());
      }
   }
}   

Output

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

printing elements using iterator:
A
B
C
D

Example 3

The following example shows the usage of Java Deque iterator() method to iterate Student objects. We're adding couple of Student objects to the Deque object using add() method calls per element and then iterate and print each element to show the elements added.

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;

public class DequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      Deque<Student> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(new Student(1, "Julie"));
      deque.add(new Student(2, "Robert"));
      deque.add(new Student(3, "Adam"));

      // iterator() is used to print all the elements
      // next() returns the next element on each iteration
      System.out.println("printing elements using iterator:");
      for(Iterator<Student> itr = deque.iterator();itr.hasNext();)  {
         System.out.println(itr.next());
      }
   }
}
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 −

printing elements using iterator:
[ 1, Julie ]
[ 2, Robert ]
[ 3, Adam ]