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Java Java Data Structures Efficiency! Add tags to a course

Enyang Mercy
Enyang Mercy
Courses Plus Student 2,339 Points

Designing UI if tag is added to mTags

Please check the if statement Can't compile again

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) {
    // TODO: add the tag

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

  public boolean hasTag(String tag) {
    if (hasTag.add == mTags) 
    // TODO: Return whether or not the tag has been added
    return true;

  public String getTitle() {
    return mTitle;


1 Answer

Hi there,

The hasTag method receives a tag and returns true if mTags contains tag, or false otherwise.

The List class has a helpful method called .contains() which you can chain to the list variable, mTags and pass in the tag that the method receives.

This will create a true or false outcome so you can just return the result of that expression from the method.

So, take mTags, chain .contains() onto it with dot notation and pass tag into contains() inside the brackets. Return that.