What is bad smells in Java

Bad smells in Java (or "code smells") are characteristics of code that indicate that something is not quite right, and that the code may be difficult to understand, maintain, or extend in the future. These smells can be caused by a variety of factors, such as poor design, lack of encapsulation, or overuse of certain language features. Some common bad smells in Java include:

  1. Long methods: A method that is too long and complex is difficult to understand, and it may indicate that the method is doing too many things, or that it should be refactored into smaller, more focused methods.
  2. Large classes: A class that is too large and complex is difficult to understand, and it may indicate that the class has too many responsibilities or that it should be refactored into smaller, more focused classes.
  3. Duplicate code: Code that is duplicated in multiple places is difficult to maintain, and it increases the risk of introducing bugs or inconsistencies.
  4. Switch statements: Using switch statements, especially on large and complex cases, makes the code harder to understand and harder to change.
  5. Primitive obsession: A class that wraps a primitive type (e.g. Integer) instead of using the primitive type directly. This can lead to verbose and less efficient code.
  6. Hard-coded constants: Using hard-coded constants in the code makes it more difficult to change and less flexible.
  7. Lazy class: A class that does not provide any useful methods or fields, only exists to group other classes or methods.
  8. Data clumps: A group of data fields that are always used together, indicating that they should be grouped into an object.
  9. Comments: Comments that explain what the code does, instead of why it does it. Comments can also become stale and can be a maintenance problem.
  10. Unknown numbers: using the unkown numbers in the code, which are hardcoded values that have a specific meaning in the code, and can make it hard to understand the code.

These are just some examples of bad smells in Java, and there are many others. It's important to note that bad smells are not always a problem, and sometimes they are an indication of a deeper problem. The goal is to be aware of bad smells and evaluate if they are affecting the maintainability and readability of the code. It's also important to note that it's a sign of a good practice to refactor and improve the code, don't leave it as it is.