switch method in java

Question

I'm trying to use the switch method to count the number of vowels and number of consonants in a string. There is alot online for this problem but I must make sure characters like (,,$,&). numbers and spaces are not included as a consonants.

I have this atm.

  switch (ch) {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
      vowelCount ++; 
      break;
    default:
      consonantCount ++;
      break;
  }

How could I change the default to a specific case that only allows characters between a and z?

Answer 1

How could I change the default to a specific case that only allows characters between a and z?

The default case matches everything that has not be matched by other cases, and you can't change that. Non-default cases only match a single compile time constant, and you can't change that either.

So the closest you can come with a switch statement will be to use an if statement within the default case.

  switch (ch) {
  case 'a': case 'e': case 'i': case 'o': case 'u':
      vowelCount++; 
      break;
  default:
      if (ch >= 'a' && ch <= 'z') {
          consonantCount++;
      }
      break;
  }

---

As @Oliver points out in his Answer, there are other (arguably better) ways to write the above without using a switch statement. But I disagree with his characterization of if in default as "bad practice".

To my mind, the two most important things when talking about code quality are:

• The code should be correct in the sense that it does what it is supposed to do.
• The code should be sufficiently readable to whoever will need to read and maintain the code.

^{(I think we can all agree that these are necessary (if not sufficient ) for good code, but I acknowledge that I have simplified this, for the sake of argument.)}

However, reasoning that is based on "how specific constructs are intended to be used" is (IMO) based on two false assumptions:

• An assumption that the designers of Java did actually intend this... absent any documentary evidence of their intention.

• An assumption that common usage patterns in Java cannot (or should not) evolve beyond the designers' original intentions.

For these reasons, I disagree with Oliver's blanket assertion that if statements in a default are "bad practice". It depends on correctness and readability / maintainability of the code in context .

Answer 2

A switch statement is not going to solve your problem nicely.

Personally, I consider it bad practice to nest an if statement inside the default case of a switch statement and is a sign that your pattern may need tweaking. For example

if(a == b || a == c || a == d)

could be written as

switch(a) {
  case b:
  case c:
  case d:
    // Code.
    break;
}

Switch and if statements serve different purposes. If you need to check a condition on the variable you are switching in your default case, then you probably should use an if statement or add more case s.

I suggest the following:

if(ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
  vowelCount++;
} else if(ch >= 'a' && ch <= 'z') { // If the character code is between 'a' and 'z', inclusive.
  consonantCount++;
}

Answer 3

This all seems a lot cleaner if you ditch your switch.

private static final String VOWELS = "aeiou";

public void count(String in) {
    int vowel = 0, consonant = 0;
    for (char c : in.toCharArray()) {
        if (VOWELS(c) > -1) vowel++;
        else if (c >= 'a' && c <= 'z') consonant++;
    }
    System.out.printf("Vowels: %d Consonants: %d\n", vowel, consonant);
}