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Java Java Data Structures Efficiency! Add tags to a course

Enyang Mercy
PLUS
Enyang Mercy
Courses Plus Student 2,339 Points

Designing UI Fix the addTag and addTags

Stuck !!!! could you please help with correct code.

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

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

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

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

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

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

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

  public String getTitle() {
    return mTitle;
  }

}

4 Answers

Hi there,

In addTag, don't redeclare the tag as a string - it is only done once, in the method signature:

  public void addTag(String tag) {
    mTags.add(tag);
  }

In the addTags method, take the passed-in list and loop over it, pulling out each tag at a time. The list is made of strings, so define a new string local variable to hold each element of the list. Then pass that tag to the addTag method above:

for(String tag : tags){
  // call the above method and pass in 'tag'
}

The comment directs the final line of code.

Let me know how you get on.

Steve.

Seth Kroger
Seth Kroger
56,405 Points

Just a quick comment that Lists do have an addAll() method that takes another collection, so you can skip the for loop and just use:

mtags.addAll(tags);

Some times a look at the docs can give you an easier way.

That's a very good shout - thanks, Seth!

Enyang Mercy
PLUS
Enyang Mercy
Courses Plus Student 2,339 Points

I couldn't compile. I'm stuck again

for(String tag : tags) {
String tag = new String(tag);     string variable
mTags.addTag(tag)

You've done the for loop correctly. Inside it just call addTag and pass tag to it. You can delete the String line inside the loop - the new variable is created in the brackets of the for loop; it is called tag:

for(String tag : tags){
  addTag(tag);
}

Steve.