Code Smells Reference

24 Classic Code Smells

Based on the book "Refactoring: Improving the Design of Existing Code", this collection covers all classic code bad smells. Each bad smell includes detailed explanations and Java example code to help you quickly identify and understand them.

🧱

Bloaters

5 items

Primitive Obsession

基本类型偏执

Overuse of basic primitive types instead of creating small objects to represent domain concepts.

The same group of data items always appears together in multiple places.

A class contains too many fields, methods, or lines of code, violating the Single Responsibility Principle.

A function is too long, making it hard to read and maintain—usually a sign multiple responsibilities haven't been split.

Long Parameter List

过长参数列表

A function has too many parameters, making it hard to understand and use.

🧩

Object-Orientation Abusers

4 items

Temporary Field

Object-Orientation Abusers

Some fields in an object only have meaningful values in specific situations.

Alternative Classes with Different Interfaces

异曲同工的类

Object-Orientation Abusers

Two classes have similar functionality but different interfaces.

Refused Bequest

被拒绝的遗赠

Object-Orientation Abusers

A subclass does not use (or rejects) some of the methods or data it inherits from its parent.

Repeated Switches

重复的 switch

Object-Orientation Abusers

Complex switch statements that could typically be replaced by polymorphism.

🛑

Change Preventers

4 items

Divergent Change

发散式变化

Change Preventers

A class needs to be modified frequently for different, unrelated reasons.

Change Preventers

Modifications to data often lead to unexpected results and hard-to-find bugs, where updating data in one place affects expectations elsewhere in the software.

Mysterious Name

Change Preventers

Functions, modules, variables, or classes have names that don't clearly express what they do.

Shotgun Surgery

霰弹式修改

Change Preventers

Whenever a change is needed, small edits must be made across many different classes.

🧹

Dispensables

6 items

冗赘的元素

Program elements (like classes and functions) no longer provide enough value to justify their existence and should be inlined or removed.

Speculative Generality

夸夸其谈通用性

Overly complex structures designed for potential future needs that may never arrive.

Traditional loop statements are outdated, modern functional programming provides clearer pipeline operations to replace loops.

Too many comments in the code usually indicate that the code is not clear enough.

The class only contains fields and accessor methods and has no other functionality.

The same code structure appears repeatedly in multiple places.

🔗

Couplers

5 items

Most of a class's methods simply delegate to other classes.

A method is more interested in the data of other classes than the data of its own class.

Global data can be modified from anywhere in the codebase, and there's no mechanism to detect which code made the modifications.

Insider Trading

Excessive private data exchange between modules increases coupling and should be reduced with transparent communication mechanisms.

过长的消息链

The client needs to obtain the required object through a long chain of method calls.