Lazy Class

Description (What)

A lazy class is a class that doesn't do much or doesn't contribute enough to warrant your attention.

How to Locate It (Where)

Find classes that appear small, have limited interaction with the rest of the program and don't contribute to the overall program.

How It Manifests (Why)

Classes that were originally designed to support some future work or have reduced in size by a lot after refactoring.

How to Fix It (Possible Treatments)

In Example 1, Collapse Hierarchy is used to remove the Lazy Class. Collapse Hierarchy works by removing a superclass that is not doing much more than simply than existing for the sake of hierarchy in the case of Lazy Class.

In Example 2, Collapse Hierarchy is also used to remove the unnecessary class. When there are some additional layers in the architecture,

but the extra layers are rarely used, developers could consider get rid of the complexity.

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

Examples

Example 1

Before:

Cheetah was added considering that it might have unique functionality in the future.

Observed Code Smells:
- Lazy Class (lines 29-33)

After:

Applied Collapse Hierarchy to remove the class given that it is the same as the super class Cat

Refactoring Applied:
- Lazy Class
    - Collapse Hierarchy (Cheetah)

Observed Code Smells After Refactoring:
- None

Example 2

Before:

The subclass Security of the class Employee does not seem to do enough to earn attention at this time.

It only comes with an additional field which is badgeNumber.

Observed Code Smells:
- Lazy Class (line 76-91)

After:

Applied Collapse Hierarchy to merge the subclass into the superclass.

Refactoring Applied:
- Lazy Class:
    - Collapse Hierarchy (line 88-90, 27-37)

Observed Code Smells After Refactoring:
- None

When to Ignore

In cases where classes are created in specific cases to project future work or extensions

More about Lazy Class

Example 1
Example 2

Before
After

001  class Cat {
002      private String name;
003      private String cry;
004  
005      public Cat(String name, String cry) {
006          this.name = name;
007          this.cry = cry;
008      }
009  
010      public void purr() {
011          System.out.println(this.cry);
012      }
013  
014      public void getCatName() {
015          System.out.println(this.name);
016      }
017  }
018  
019  class Tiger extends Cat {
020      public Tiger(String name, String cry) {
021          super(name, cry);
022      }
023  
024      public void isDangerous() {
025          System.out.println("Yes");
026      }
027  }
028  
029  class Cheetah extends Cat {
030      public Cheetah(String name, String cry) {
031          super(name, cry);
032      }
033  }
034  
035  public class LZCBE1 {
036      public static void main(String[] args) {
037          Cat cat = new Cat("Siamese", "Meow");
038          Tiger tiger = new Tiger("Bengal", "Roar");
039          Cheetah cheetah = new Cheetah("African", "Meow");
040          cheetah.purr();
041          cat.purr();
042          tiger.purr();
043      }
044  }
045