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Java Java Data Structures Efficiency! Don't Stop Believin'

Deividas Strioga
Deividas Strioga
12,851 Points
Posted by Deividas Strioga
Deividas Strioga
12,851 Points

Please help with challenge task 3

This is what i have done: 

import com.example.model.Course;
import com.example.model.Video;

import java.util.Map;
import java.util.HashMap;

public class QuickFix {

  public void addForgottenVideo(Course course) {
    Video video = new Video("The beginning bits");
    int index = 1;
    course.getVideos().add(index, video);

    // TODO(1):  Create a new video called "The Beginning Bits"

    // TODO(2):  Add the newly created video to the course videos as the second video.

  }

  public void fixVideoTitle(Course course, String oldTitle, String newTitle) {
    if (videosByTitle(course).containsKey(oldTitle)); {
      videosByTitle(course).put(newTitle, videosByTitle(course).get(oldTitle));
      videosByTitle(course).remove(oldTitle);
    } 
  }

  public Map<String, Video> videosByTitle(Course course) {
    Map<String, Video> byTitle = new HashMap<>();
    for (Video video : course.getVideos()){
      byTitle.put(video.getTitle(), video); 
    }
    return byTitle;
}
}

Task 3 asks to fix fixVideoTitle method. There is no compilation error, but when i try to check the answer, it says Bummer! Are you sure you updated the videos title? Why my method doesn't change the title?

Thanks in advance.

Ronnie Barua
Ronnie Barua
17,665 Points
Ronnie Barua
Ronnie Barua
17,665 Points

You are missing a carly brace.

2 Answers

Grigorij Schleifer
Grigorij Schleifer
10,365 Points
Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hi Deividas,

here my QuickFix.class:

import com.example.model.Course;
import com.example.model.Video;
import java.util.Map;
import java.util.HashMap;

import java.util.Map;

public class QuickFix {

  public void addForgottenVideo(Course course) {
      Video video = new Video("The beginning Bits");
      course.getVideos().add(1, video);
  }

    public void fixVideoTitle(Course course, String oldTitle, String newTitle) {
      Video videoValue = videosByTitle(course).get(oldTitle);
// store the old titled video in videoValue
      videoValue.setTitle(newTitle);
// change the state of videoValue to new Title
  }


  public Map<String, Video> videosByTitle(Course course) {
    Map<String, Video> byTitle = new HashMap<>();
    for (Video video: course.getVideos()) {
     byTitle.put(video.getTitle(), video); 
    }
    return byTitle;
  }
}

I have changed my fixVideoTitle method and made it more readable :)

Let me know if it was helpfull

Grigorij

Deividas Strioga
Deividas Strioga
12,851 Points
Deividas Strioga
Deividas Strioga
12,851 Points

Just before i saw this code i passed the challenge with this fixVideoTitle method (inspired by your last post): 

public void fixVideoTitle(Course course, String oldTitle, String newTitle) {
    for (Video video : course.getVideos()){
    if (videosByTitle(course).containsKey(oldTitle)); {
      video.setTitle(newTitle);
    } 
  }
  }

Your code works as well, and it is way more simpler! I guess I over-complicate the code :) Thank you so much for your help and support Grigorij! Good luck with your tasks!

Grigorij Schleifer
Grigorij Schleifer
10,365 Points
Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hey Deividas,

thank you too !

For answering your question I repeated the challenge and created this new simpler approach :)

See you in the forum !

Grigorij

Denis Migounov
Denis Migounov
17,657 Points
Denis Migounov
Denis Migounov
17,657 Points

Hi Grigorij, I think that, having changed a video title in fixVideoTitle, we need to rebuild the HashMap by calling videosByTitle(course), otherwise the map would still contain oldTitle as a key and we wouldn't be able to find newTitle in the map.

Grigorij Schleifer
Grigorij Schleifer
10,365 Points
Grigorij Schleifer
Grigorij Schleifer
10,365 Points

HI Deividas,

try this:

public void fixVideoTitle(Course course, String oldTitle, String newTitle) {
      Map<String, Video> map = videosByTitle(course);
// creating a Map and using the videoByTitle method to generate a Map
        for (Video vid: course.getVideos()) {
// „for every video in all videos from the course“
         if (vid.getTitle().equals(oldTitle)) {
// vid.getTitle() gets you the title from every video
// equals(oldTitle) and compares it with the old title
// so if  the condition is true (vid.getTitle() gives you  a title that is equal to oldTitle
           vid.setTitle(newTitle);
// set a new title
// baaaaaaaaam !!!
        }
    }

Hope that helps

Grigorij

Deividas Strioga
Deividas Strioga
12,851 Points
Deividas Strioga
Deividas Strioga
12,851 Points

Hey Grigorij,

Thank you for your answer. But your code doesn't work as well :) The task asks to use previously created videosByTitle(Course course) method. Any thoughts?

Danilo ANRIA
Danilo ANRIA
1,571 Points
Danilo ANRIA
Danilo ANRIA
1,571 Points

why did you create the map ? I passed the challenge without using the videosbyTitle() map. I could not find a way to use it properly until I saw Deividas Strioga use the containsKey() method.