#Clean Code

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Clean Code

Any fool can write code a system can understand. Good programmers write code that humans can understand.

• Martin Fowler

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Be predictable!

No Side Effects!

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Meaningful Descriptive Names

• Classes should be nouns
• Methods should be verbs
• Descriptive name over detailed comments

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Meaningful Descriptive Names

int d; // elapsed time in days

VS

int elapsedTimeInDays;

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Meaningful Descriptive Names

What is this doing?

public List flags() {
   List list1 = new ArrayList();
   for (int[] x : this.theList){
    if (x[0] == 4) {
    list1.add(x);
    }
   }
   return list1;
}

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Meaningful Descriptive Names

• What is this doing? ```java public List getFlaggedCells() { List flaggedCells = new ArrayList(); for (int[] cell : this.gameBoard) { if (cell[STATUS_VALUE] == FLAGGED) { flaggedCells.add(cell); } } return flaggedCells; }

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# Single Responsibility
- Do one thing
  - variable
  - method
  - class
  - test




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# Small methods
- Do one thing (SRP)
  - change the state of an object
  - get information about that object
- Less than 20 lines
- Maximum of 3 params

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# One word per concept
- Length / size
- fetch / retrieve / get

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# Testable
- Write the test, then write to code to make the test pass
- Tests should be
    - Fast
    - Independent - no test should depend on another test
    - Repeatable - can run in any environment
    - Self-validating (assert pass or fail, no manual check)
    - Timely (don’t write your test too late)

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# Don’t repeat yourself! (DRY)
Sharing is caring


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# Comments
- Express yourself in code
- Use comments to explain why not
  ```java
    // This test is extremely slow, only run it when you have time

• Use comments to warn others

    // This makes an actual call to production API
  

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Formatting

• Read top to bottom
• Constants, instance variable, methods
• Related concepts should be close to each other
• Variables should be declared as close to their usage as possible

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Encapsulation

• A mechanism of wrapping the data (variables) and code acting on the data (methods) together as a single unit

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Conclusion

• Write readable code
• Meaningful names
• Write the test, write the code to make it work, then clean it!
• Do one thing and do it well (Single Responsibility Principle)
• No side effect
• DRY (Don’t Repeat Yourself)
• KISS (Keep It Simple, Stupid)

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Follow the boyscout rule:

“Leave the code cleaner than you found it.”