Change Extension (string)

Problem: Change the extension of a file name

//============================================== changeExtension
    // changes extension to new extension
    // example: x = changeExtension("data.txt", ".java")
    //         will assign "data.java" to x.
static String changeExtension(String originalName, String newExtension) {
    int lastDot = originalName.lastIndexOf(".");
    if (lastDot != -1) {
        return originalName.substring(0, lastDot) + newExtension;
    } else {
        return originalName + newExtension;
    }
}//end changeExtension