Welcome to the Java Programming Forums


The professional, friendly Java community. 21,500 members and growing!


The Java Programming Forums are a community of Java programmers from all around the World. Our members have a wide range of skills and they all have one thing in common: A passion to learn and code Java. We invite beginner Java programmers right through to Java professionals to post here and share your knowledge. Become a part of the community, help others, expand your knowledge of Java and enjoy talking with like minded people. Registration is quick and best of all free. We look forward to meeting you.


>> REGISTER NOW TO START POSTING


Members have full access to the forums. Advertisements are removed for registered users.

Results 1 to 3 of 3

Thread: Question : Collection

  1. #1
    Junior Member
    Join Date
    Dec 2012
    Posts
    1
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default Question : Collection

    How can allow duplicate value in set show by doing program....


  2. #2
    Super Moderator Norm's Avatar
    Join Date
    May 2010
    Location
    SW Missouri
    Posts
    20,592
    Thanks
    50
    Thanked 2,235 Times in 2,207 Posts

    Default Re: Question : Collection

    A Set does not have duplicate elements.
    Can you explain what you are trying to do?
    An ArrayList can have duplicate values.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
    Super Moderator helloworld922's Avatar
    Join Date
    Jun 2009
    Posts
    2,896
    Thanks
    23
    Thanked 619 Times in 561 Posts
    Blog Entries
    18

    Default Re: Question : Collection

    A set's definition is a collection of unique items, so it doesn't make sense to have duplicate values.

    There are things known as "multi-sets" or "multi-maps" which do allow duplicate values, but there are no standard implementations in Java.

    The simplest way to get something that appears like a multi-map is to create a map with a List for each key. See: The Java Tutorials: The Map Interface

Similar Threads

  1. collection problem
    By freakycoder in forum Collections and Generics
    Replies: 13
    Last Post: June 26th, 2012, 11:05 AM
  2. When use Collection Framework?
    By hexwind in forum Java Theory & Questions
    Replies: 7
    Last Post: July 31st, 2011, 04:19 PM
  3. Synchronized Collection
    By tcstcs in forum Java Theory & Questions
    Replies: 2
    Last Post: March 29th, 2011, 12:09 AM
  4. Looking for Collection class to do first if first out
    By snytkine in forum Collections and Generics
    Replies: 5
    Last Post: October 7th, 2010, 09:18 PM
  5. Garbage Collection?
    By kalees in forum Collections and Generics
    Replies: 6
    Last Post: September 23rd, 2009, 03:07 AM