Converting given string to camel case recursively

Question

Basically I want to recursively get this:

“ pErHaPs I hAVe wRitten a Sentence LiKE this one “

To look like this:

“perhapsIHaveWrittenASentenceLikeThisOne”

• n>0 of spaces before, between, and after each word
• any assortment of upper-case and lower-case letters ex: " lIkE ThIs"

What I think I understand:

• Using string.charAt(i) to compare the specific character to a space
• Using Character.isUpperCase() for case checking

What I don't understand:

• How recursion will work to change the string since strings are immutable

• What the base case will be

• how to only uppercase the first letter of every word after the first word

EDIT: This is what I have come up with after a few helpful hints: `public static String toCamelCase(String str) {

    if(str.length() == 1) {
        if(str.charAt(0) == ' ') {
            return "";
        } else {
            return str;
        }
    } else if(str.charAt(0) == ' ' && str.length() != 1) {
        if(str.charAt(1) != ' ') {
            return str.substring(1, 2).toUpperCase() + toCamelCase(str.substring(2, str.length()));
        } else {
            return toCamelCase(str.substring(1, str.length()));
        }
    } else if(str.charAt(0) != ' ' && str.length() != 1) {
        if(str.charAt(1) != ' ') {
            return str.substring(0,2).toLowerCase() + toCamelCase(str.substring(2, str.length()));
        } else {
            return str.substring(0,1).toLowerCase() + toCamelCase(str.substring(1, str.length()));
        }
    }
    return str;
}`

Everything works except the first letter of the first word is also capitalized. How would I make the code exclude the first word when uppercasing first letters of words? Is this possible recursively?

Answer 1

There you go with your recursive implementation:

public String camelCase(String inputStr) {
   String s = inputStr.toLowerCase();
   String[] arr = s.split(" "); 
   s = arr[0];
   return getCamelCased(s,1,arr);
}

private String getCamelCased(String s, int index, String[] arr) {
   if(index >= arr.length)
        return s;

   String curr = arr[index++];
   s += curr.length()==1?curr.toUpperCase(): 
   (curr.toUpperCase.charAt(0)+curr.substring(1,curr.length()));

   return getCamelCased(s,index,arr);
}