public void setClassHandler(String className, Handler handler) {
        className = className.toLowerCase();

        if (handler == null) {
            classHandlers.remove(className);
        } else {
            classHandlers.put(className, handler);
        }
    }
Finds first occurrence of unicode character and returns its index or {@code -1} otherwise.
exts/jphp-json-ext/src/main/java/org/develnext/jphp/json/gson/MemorySerializer.java