StringIndexOutOfBoundsException -1 when checking last letter of a word

Question

I'm trying to solve a problem on coding bat and cannot pass one test.

Given a string, count the number of words ending in 'y' or 'z' -- so the 'y' in "heavy" and the 'z' in "fez" count, but not the 'y' in "yellow" (not case sensitive). We'll say that ay or z is at the end of a word if there is not an alphabetic letter immediately following it. (Note: Character.isLetter(char) tests if a char is an alphabetic letter.)

Here is my code:

public int countYZ(String str) {
int count = 0;
str = str.toLowerCase();
String[] newArr = str.split("[\\s:0-9-!]+");
for (String word : newArr) {
  if (word.charAt(word.length() - 1) == 'y' || 
    word.charAt(word.length() - 1) == 'z') {
    count++;
    }
  }
    return count;
}

However I cannot pass this test and it shows this error:

countYZ("!!day--yaz!!") → 2

Exception:java.lang.StringIndexOutOfBoundsException: String index out of range: -1 (line number:6)

Answer 1

Exception:java.lang.StringIndexOutOfBoundsException: String index out of range: -1 (line number:6) means that you're calling -1 th index.

You're calling always charAt(word.length()-1) so if word.length()-1 == -1 , word.length() == 0 . Add a check if word.length()>0 before checking last letter.

It's caused by the following slicing:

!!day--yaz!!
["day", "yaz", ""]

For example you can write:

for (String word : newArr) {
  if (word.length() > 0 && (word.charAt(word.length() - 1) == 'y' || 
    word.charAt(word.length() - 1) == 'z')) {
    count++;
    }
  }
    return count;
}

or simpler (according to Ole 's idea):

for (String word : newArr) {
  if (word.endsWith("y") || word.endsWith("z")) {
    count++;
    }
  }
    return count;
}