How can i extract a word using loops and not arrays

Question

Situation:

A user will input a sentence. I need to perform certain modifications to each word but depending on the length of each word.

For example for each vowel i need to put a 3 before if the word length is over 2.

// for words with length > 2
for (i=0;i<example.length();i++)

    switch (word.charAt(i))
    {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
    case 'y':
        output += "3" + word.charAt(i);
        break;
    default:
        output += word.charAt(i);
        break;
    }

Objective:

How can i test a word's length before i perform my for loop. Say my word is 1-character long, i need to put a "1", 2-character long a "2".

Example:

"hello my name is roger"

Output:

h3ell3o m2y n3am3e 2is 1A

Important:

No arrays, only for, while loops, switch or if statements.

Answer 1

public class Test {
  public static void main(String[] args) {
     String input = "hello my name is roger";
     input+=' '; // adding a whitespace at end to indicate completion of last word

     String word = "";
     char ch;
     String res = "";
     int len = input.length();

     for(int i = 0;i<len ;i++) {
       ch = input.charAt(i);
       if(Character.isWhitespace(ch)) {
         res = res +" "+processWord(word);
         System.out.println(word);
         word = "";
       }else {
         word+=ch;
       }
     }
}

  private static String processWord(String word) {
    // TODO Auto-generated method stub
    if(word.length()<=2) {
      return word;
    }

    // do whatever you have to do with your word
    String res = "";
    return res;
  }
}

Basically,The logic to extract out words is -

1. if current character is a whitespace,then we've got a word.
2. else if current character is not a whitespace,then we append this character to current word that we are building