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"default" Clauses Should Be Last in Switch Statements

Medium
maintainabilityreadability

What is it?​

This practice ensures that default clauses in switch statements appear as the last case, thereby improving readability and helping developers quickly locate the default logic applied when no other cases match.

Why apply it?​

Having the default clause at the end of a switch statement emphasizes its role as a fallback and enhances the readability of the code by ensuring a logical flow from specific cases to the catch-all default.

How to fix it?​

Place the default clause as the last case within each switch statement to clearly separate specific logic from catch-all logic.

Examples​

Example 1:​

Negative​

This negative example has the default clause before other case clauses, making it harder to discern that it is the fallback option.

switch (day) {
  default:  /* Noncompliant */
    System.out.println("Unknown day");
    break;
  case "Monday":
    System.out.println("Start of the work week");
    break;
  case "Tuesday":
    System.out.println("Second day of work week");
    break;
  case "Wednesday":
    System.out.println("Mid-week day");
    break;
}

Example 2:​

Positive​

This positive example places the default clause at the end, ensuring that the most general case appears after all specific cases.

switch (day) {
  case "Monday":
    System.out.println("Start of the work week");
    break;
  case "Tuesday":
    System.out.println("Second day of work week");
    break;
  case "Wednesday":
    System.out.println("Mid-week day");
    break;
  default:  /* Compliant */
    System.out.println("Unknown day");
}

Negative​

In this negative example, the default clause is misplaced, appearing before the specific case clauses.

switch (fruit) {
  default:  /* Noncompliant */
    System.out.println("Unknown fruit");
    break;
  case "Apple":
    System.out.println("Fruit is apple");
    break;
  case "Banana":
    System.out.println("Fruit is banana");
    break;
  case "Orange":
    System.out.println("Fruit is orange");
    break;
}

Example 3:​

Positive​

In this positive example, the default clause is correctly placed after all specific cases, making the order of matching clear.

switch (fruit) {
  case "Apple":
    System.out.println("Fruit is apple");
    break;
  case "Banana":
    System.out.println("Fruit is banana");
    break;
  case "Orange":
    System.out.println("Fruit is orange");
    break;
  default:  /* Compliant */
    System.out.println("Unknown fruit");
}