Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Data Structures Efficiency! Add tags to a course

Posted by Dax Stucki
Dax Stucki
1,034 Points

I've created the method to add a tag to mTags. How do I add all the tags using the addTags method?

I think what I have to do is add List items to a HashSet. I'm just not sure how...

thanks Dax

com/example/model/Course.java 
package com.example.model;

import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Course {
  private String mTitle;
  private Set<String> mTags;

  public Course(String title) {
    mTitle = title;
    // TODO: initialize the set mTags
    mTags = new HashSet<String>();
  }

  public void addTag(String tag) {
    // TODO: add the tag
    mTags.add(tag);
  }

  public void addTags(List<String> tags) {
    // TODO: add all the tags passed in
    mTags = mTags.add(tags);
  }

  public boolean hasTag(String tag) {
    // TODO: Return whether or not the tag has been added
    return false;
  }

  public String getTitle() {
    return mTitle;
  }

}

2 Answers

Daniel Santos
Daniel Santos
34,969 Points

Hey Dax,

I took a look at your code, and problem that I noticed is that you are trying to add a List<String> in to a HashSet<String>, so that won't work. Here is an example of something that worked for me. I used an enhanced for loop;

  public void addTag(String tag) {
    // TODO: add the tag
    mTags.add(tag);
  }

  public void addTags(List<String> tags) {
    // TODO: add all the tags passed in
    for (String tag : tags) {
      mTags.add(tag);
    }
  }

  public boolean hasTag(String tag) {
    // TODO: Return whether or not the tag has been added
    return mTags.constains(tag;
  }

If you have any question let me know

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

In the hasTag method, you need to tidy up your code a little. The concept is correct but the code isn't quite right. Rather than having:

    return mTags.constains(tag;

change that to: 

return mTags.contains(tag);

Steve.