Skip to main content

Lazy Class

A "Lazy Class" is a freeloader. It’s a component that doesn't do enough to justify its existence. Maybe it used to be important, but after refactoring, it lost most of its responsibilities. Or maybe it was designed for a future feature that never arrived.

Each class in your project adds complexity and maintenance cost. If a class isn't pulling its weight, it should be fired (or inline-d).

Signs of the Smell​

  • A class that has very few methods or fields.
  • A class that is only used by one other class and does very little.
  • A subclass that doesn't add any new behavior to its parent.

Reasons of the Smell​

Refactoring Residue: You moved code out of this class, leaving it empty. Over-Design: You created a class structure for a "planned" feature that never got built.

Refactoring Recipe​

  • Inline Class
  • Collapse Hierarchy

Inline Class​

If a class is too small, merge it into the class that uses it most.

Before:

class Person {
    private Office office;
    public String getOfficeAreaCode() {
        return office.getAreaCode();
    }
}

class Office { // Lazy Class!
    private String areaCode;
    public String getAreaCode() { return areaCode; }
}

After:

class Person {
    private String officeAreaCode; // Merged into Person
    public String getOfficeAreaCode() { return officeAreaCode; }
}

Collapse Hierarchy​

If a subclass and superclass are nearly practically identical, merge them.

Before:

class Employee { ... }
class Salesman extends Employee { } // Adds nothing?

After:

class Employee { ... } // Combined

References​