snakeCaseFormat Java

snakeCaseFormat.java

private static String snakeCaseFormat(String name) {
        final StringBuilder result = new StringBuilder();

        boolean lastUppercase = false;

        for (int i = 0; i < name.length(); i++) {
            char ch = name.charAt(i);
            char lastEntry = i == 0 ? 'X' : result.charAt(result.length() - 1);
            if (ch == ' ' || ch == '_' || ch == '-' || ch == '.') {
                lastUppercase = false;

                if (lastEntry == '_') {
                    continue;
                } else {
                    ch = '_';
                }
            } else if (Character.isUpperCase(ch)) {
                ch = Character.toLowerCase(ch);
                // is start?
                if (i > 0) {
                    if (lastUppercase) {
                        // test if end of acronym
                        if (i + 1 < name.length()) {
                            char next = name.charAt(i + 1);
                            if (!Character.isUpperCase(next) && Character.isAlphabetic(next)) {
                                // end of acronym
                                if (lastEntry != '_') {
                                    result.append('_');
                                }
                            }
                        }
                    } else {
                        // last was lowercase, insert _
                        if (lastEntry != '_') {
                            result.append('_');
                        }
                    }
                }
                lastUppercase = true;
            } else {
                lastUppercase = false;
            }

            result.append(ch);
        }
        return result.toString();
    }