i am not able to find the problem

package com.example.model;
import java.util.List;

public class Course {
  private String mName;
  private List<Video> mVideos; 

  public Course(String name, List<Video> videos) {
    mName = name;
    mVideos = videos;
  }

  public String getName() {
    return mName;
  }

  public List<Video> getVideos() {
    return mVideos;
  }

}

package com.example.model;

public class Video {
  private String mTitle;

  public Video(String title) {
    mTitle = title;
  }

  public String getTitle() {
    return mTitle;
  }

  public void setTitle(String title) {
    mTitle = title;
  }

}

import com.example.model.Course;
import com.example.model.Video;
import java.util.TreeMap;
import java.util.ArrayList;
import java.util.Map;

public class QuickFix {

  public void addForgottenVideo(Course course) {
    // TODO(1):  Create a new video called "The Beginning Bits"
course.getVideos().add(1, new Video("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) {
       Map<String, Video> byTitle;
    videosByTitle(course);
    Video video = new Video("i can't make you love me");
    if(newTitle == oldTitle){
  System.out.println("this song already exits");
  }else{
  byTitle.put(video.getTitle(),video);
  }
  }

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

}