Validation for capitalizeFirstChar

[pvs1209pvs]

Return the original string if the input is a blank string or empty.

[Carleslc]

if input is trimmed then isEmpty is equivalent to isBlank, so isEmpty is enough

[Carleslc]

Trim only removes prefix and suffix spaces, so changing the split " +".toRegex() to " " this line gives error when there is more than one space between characters, for instance:

" aa   bb  cc dd ".capitalizeFirstChar()
// NoSuchElementException: Char sequence is empty.

Error is in the first method with an empty split, although when using anything else like d.replaceRange(0, 1, "A") the replaceRange method also fails with: IndexOutOfBoundsException: start 1, end 0, length 0

What should be the correct output?

1. Aa Bb Cc Dd (with trim, removing extra spaces)
2.  Aa Bb Cc Dd  (without trim, removing extra spaces)
3. Aa Bb Cc Dd (with trim, preserving extra spaces)
4.  Aa Bb Cc Dd  (without trim, preserving extra spaces)

For the 4th output (preserving everything in the original string but with the first char of every word to uppercase which is the purpose of this method), this would do it:

fun String.capitalizeFirstChar(): String {
    if (isBlank()) return this
    
    return lowercase(Locale.getDefault())
        .split(" ")
        .joinToString(" ") { d ->
            if (d.isEmpty()) d else d.replaceRange(0, 1, d.first().uppercaseChar().toString())
        }
}

Also the replaceRange and toString can be changed to d.first().uppercaseChar() + d.substring(1), whatever you prefer.

Changing the split to the previous " +".toRegex() then the output would be the 2nd.

Trimming I think should be done outside this method so the intentions of the code are more clear.

[pvs1209pvs]

I have made the following changes

• Caller is responsible for trimming the string.
• Caller and choose to preserve the spacing.
• Exception is thrown for empty and blank strings.
• Appropriate tests are written.