Solved

Need a container to hold a unique list of strings with a fast lookup

Posted on 2004-07-31
5
227 Views
Last Modified: 2012-05-05
Hi,

I need to maintain a list of unique strings. What container should I use? I need the following requirements:

1) check to see if the string exists in the container (note that it could be a different String object with the same text)
2) must be fast. I mean I don't want the container to be looping through each element doing an equals() call for each element

So I'm thinking it should be some kind of container where the Strings are added in sorted order. This way any kind of equals call can use a divide and conquer approach to testing or something similar.

Are there any containers like this? Whether inside the JDK or freely available somewhere?

Or does anyone have any suggestions the best way to build one?
0
Comment
Question by:ycomp
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
5 Comments
 
LVL 7

Accepted Solution

by:
lhankins earned 500 total points
ID: 11686237
You can do this with one of the java.util.Set implementations (either HashSet or TreeSet).

Both implementations are fast with respect to lookup time.   If you want to maintain the items in sorted order (e.g. you want to print them out in sorted order), then use the TreeSet.   Otherwise, use the HashSet.

Example usage :

      Set items = new HashSet();

      items.add("foo");
      items.add("bar");
      items.add("wubba");
      // etc...
     
      if (items.contains("somestring"))
      {
         // item is in the set...
      }


0
 
LVL 7

Expert Comment

by:lhankins
ID: 11686241
BTW - all of the classes listed above are part of the standard JDK (they are in the java.util package).
0
 

Author Comment

by:ycomp
ID: 11686246
ah, so HashSet does use equals() or something to test? I tried it in my code but it didn't work. I guess I was calling it wrong.
0
 

Author Comment

by:ycomp
ID: 11686247
I forgot about hashcodes. It's been a long day.
0
 

Author Comment

by:ycomp
ID: 11686256
yeah was my faulty code that caused the problem
0

Featured Post

Instantly Create Instructional Tutorials

Contextual Guidance at the moment of need helps your employees adopt to new software or processes instantly. Boost knowledge retention and employee engagement step-by-step with one easy solution.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

This was posted to the Netbeans forum a Feb, 2010 and I also sent it to Verisign. Who didn't help much in my struggles to get my application signed. ------------------------- Start The idea here is to target your cell phones with the correct…
Introduction This article is the last of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers our test design approach and then goes through a simple test case example, how …
Video by: Michael
Viewers learn about how to reduce the potential repetitiveness of coding in main by developing methods to perform specific tasks for their program. Additionally, objects are introduced for the purpose of learning how to call methods in Java. Define …
Viewers will learn about if statements in Java and their use The if statement: The condition required to create an if statement: Variations of if statements: An example using if statements:
Suggested Courses

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question