Feature Envy

Description (What)

When one method accesses the data of another object more than it does itself

How to Locate It (Where)

Look for methods where an object's fields or methods (objects either from the class' fields or passed through parameters) are used more than it's own classes fields or methods.

How It Manifests (Why)

It might be easier to use another object's fields or methods directly in the method of an object.

How to Fix It (Possible Treatments)

In Example 1, Move Method treatment is used. This treatment is applied when a method that is being called a lot by another class' method is actually better suited to that class itself. Doing this reduces the number of calls to another object and keeps changes easier and restricted to a single class.

In Example 2, Move Method treatment is also used for the same reasons.

Other treatments are also possible based on the specific scenario, they can be found here

Examples

Example 1

Before:

The data of Record class, specifically genre, name and duration is accessed far more by the class RecordPlayer than RecordPlayer is accessing its own data

Observed Code Smells:
- Feature Envy (lines 57-61, 63-66)

After:

Used Move Method to move getFormattedDuration() and getCurrentRecordDetails() to the Record class as it is better suited.

Refactoring Applied:
- Feature Envy
    - Move Method (getFormattedDuration, getCurrentRecordDetails)

Observed Code Smells After Refactoring:
- None

Example 2

Before:

The method generateUsageReport in class SignalProcessor currently generate report by accessing data from

methods in class RemoteController, which makes a Feature Envy code smell.

We can move the functionality of generating report back to the class RemoteController and remove the

related getter methods in class RemoteController.

Observed Code Smells:
- Feature Envy (lines 57-61, 63-66)

After:

Applied Move Method to move the envied feature back to the class from which the data comes from.


Refactoring Applied:
- Feature Envy:
    - Move Method (line 50-77)

Observed Code Smells After Refactoring:
- None

When to Ignore

In cases where there is use of the Strategy Pattern or Visitor Pattern. Also in cases of Data Access Objects

More about Feature Envy

Example 1
Example 2

Before
After

001  import java.time.Year;
002  
003  enum Genre {
004      POP,
005      ROCK,
006      HIPHOP,
007      RNB,
008      EDM
009  }
010  
011  enum PlaybackState {
012      STOPPED,
013      PLAYING,
014      PAUSED
015  }
016  
017  class Record {
018      private String name;
019      private Genre genre;
020      private int duration;
021      private Year releaseYear;
022  
023      public Record(String name, Genre genre, int duration, Year releaseYear) {
024          this.name = name;
025          this.genre = genre;
026          this.duration = duration;
027          this.releaseYear = releaseYear;
028      }
029  
030      public String getName() {
031          return this.name;
032      }
033  
034      public boolean isReleased() {
035          return this.releaseYear.isBefore(Year.now()) || this.releaseYear.equals(Year.now());
036      }
037  
038      public int getDuration() {
039          return this.duration;
040      }
041  
042      public Genre getGenre() {
043          return this.genre;
044      }
045  
046  }
047  
048  class RecordPlayer {
049      private Record currentRecord;
050      private PlaybackState state;
051  
052      public RecordPlayer(Record initialRecord) {
053          this.currentRecord = initialRecord;
054          this.state = PlaybackState.STOPPED;
055      }
056  
057      private String getFormattedDuration() {
058          int minutes = this.currentRecord.getDuration() / 60;
059          int seconds = this.currentRecord.getDuration() % 60;
060          return String.format("%d min %02d sec", minutes, seconds);
061      }
062  
063      public String getCurrentRecordDetails() {
064          String details = currentRecord.getName() + " - " + currentRecord.getGenre() + " - " + getFormattedDuration();
065          return details;
066      }
067  
068      public void playRecord() {
069          if (this.state == PlaybackState.PLAYING) {
070              System.out.println("Already playing");
071          } else {
072              System.out.println("Playing: " + currentRecord.getName());
073              this.state = PlaybackState.PLAYING;
074          }
075      }
076  
077      public void stopRecord() {
078          if (this.state == PlaybackState.STOPPED) {
079              System.out.println("Already stopped");
080          } else {
081              System.out.println("Stopped playing: " + currentRecord.getName());
082              this.state = PlaybackState.STOPPED;
083          }
084      }
085  
086      public void pauseRecord() {
087          if (this.state == PlaybackState.PAUSED) {
088              System.out.println("Already paused");
089          } else {
090              System.out.println("Paused: " + currentRecord.getName());
091              this.state = PlaybackState.PAUSED;
092          }
093      }
094  
095      public void changeRecord(Record newRecord) {
096          if (this.state != PlaybackState.STOPPED) {
097              System.out.println("Please stop playing to change the record");
098          } else {
099              this.currentRecord = newRecord;
100              this.state = PlaybackState.PLAYING;
101              System.out.println("Started playing: " + this.currentRecord.getName());
102          }
103      }
104  }
105  
106  public class FEBE1 {
107      public static void main(String[] args) {
108          Record stairwayToHeaven = new Record("Stairway to Heaven", Genre.POP, 482, Year.of(1971));
109          Record saySo = new Record("Say So", Genre.RNB, 238, Year.of(2019));
110          RecordPlayer sony = new RecordPlayer(saySo);
111          sony.pauseRecord();
112          sony.playRecord();
113          sony.changeRecord(stairwayToHeaven);
114          sony.stopRecord();
115          sony.changeRecord(stairwayToHeaven);
116          System.out.println(sony.getCurrentRecordDetails());
117          sony.playRecord();
118      }
119  }