java 中文转Unicode并转大写

public static String letterToH(String letter) {  
        StringBuilder sb = new StringBuilder();  
        for (int i = 0; i < letter.length(); i++) {  
            char c = letter.charAt(i);  
            sb.append(Integer.toHexString(c));  
        }  
        
        return sb.toString().toUpperCase();  
    }