Collection Interface Iterators

An Iterator is an object that enables you to traverse through a collection and to remove elements from the collection selectively, if desired. You get an Iterator for a collection by calling its iterator method. The following is the Iterator interface:


    public interface Iterator
    {
    boolean hasNext();
    E next();
    void remove(); //optional
    }

The hasNext method returns true if the iteration has more elements, and the next method returns the next element in the iteration. The remove method removes the last element that was returned by next from the underlying Collection. The remove method may be called only once per call to next and throws an exception if this rule is violated.

Note that Iterator.remove is the only safe way to modify a collection during iteration; the behavior is unspecified if the underlying collection is modified in any other way while the iteration is in progress.

Use Iterator instead of the for-each construct when you need to:

Remove the current element. The for-each construct hides the iterator, so you cannot call remove. Therefore, the for-each construct is not usable for filtering.

Iterate over multiple collections in parallel.

The following method shows you how to use an Iterator to filter an arbitrary Collection — that is, traverse the collection removing specific elements:



static void filter(Collection c)
{
    for (Iterator it = c.iterator(); it.hasNext(); )
        if (!cond(it.next()))
            it.remove();
}
   

This simple piece of code is polymorphic, which means that it works for any Collection regardless of implementation. This example demonstrates how easy it is to write a polymorphic algorithm using the Java Collections Framework.

References : Oracle share on :        :  

Love to hear your Views / Guidance / Recommendations on this Post…

Explore the Technology World

Computer Programming Terminologies Computer Programming Terminology is a general word for the group of specialized words or meanings relating to Computer Programming, and also the study of such t ...Read MoreNew features in JDK 12 with IntelliJ IDEADeveloped by JetBrains (formerly known as IntelliJ) ,IntelliJ IDEA is a Java integrated development environment (IDE) for developing computer software. It is av ...Read MoreGoogle Pay API Implementation Demo for AndroidIn this youtube Channel by Android Developers ,Learn how to implement the Google Pay API for Android with just a few lines of code and how it works with your ex ...Read MoreUnit Testing in .NET Core and Azure Devops pipelineUnit testing is a software testing method by which individual units of source code, usage procedures,sets of one or more computer program modules together with ...Read MoreThe mind behind Linux & GIT : Linus TorvaldsLinus Torvalds transformed technology twice — first with the Linux kernel, which helps power the Internet, and again with Git, the source code management ...Read MoreTensorflow and deep learningWith Tensorflow ,deep machine learning transitions from an area of research into mainstream software engineering. ...Read MoreJava program to return all possible permutations from collection of distinct numbersexample of Java program to return all possible permutations from collection of distinct numbers ...Read MoreReal Time Analytics with Spring Application Development FrameworkSpring is the most popular application development framework for enterprise Java.Millions of developers use Spring to build simple, truly portable, fast and fle ...Read MorePath Setting in Java When an application is launched from command prompt Windows OS searches for the executable program in the current working directory. The prompt throws an error ...Read MoreFacebook | whatsapp|Github | Twitter | LinkedIn | Youtube| reddit About | Cookies-Policy | Disclaimer | Site Map | Contact

Call / Visit for New Batch

Services

Why Join Us

  • ➯ Free Demo Classes
  • ➯ No Registration Fee
  • ➯ Interview Questions
  • ➯ Study Materials
  • ➯ Softwares
  • ➯ Aptitude & Reasoning
  • ➯ Placement Assitance

Address

  • MyJava Training Institute ,
  • Plot No.243 , shop No 14 ,
  • Secnd Floor , Zone-II ,
  • M.P.Nagar , Bhopal,
  • Madhya Pradesh ( 462011 )
  • ☎  08871209400 , 7987028543
  • 🌐 www.myjava.in
FacebookGoogle +TwitterYouTube

MyJava - java Training Institute