#vulnerable code 
                                public static OptionType getOptionType(OptionName opt_name){
        return syntaxConstraints.get(opt_name).opt_type;
    } 
                            #location 2 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public static OptionType getOptionType(OptionName opt_name){
        OptionSyntaxConstraints osc = syntaxConstraints.get(opt_name);
        if(osc == null) {
            throw new NullPointerException("OptionSyntaxConstraints does not exists!");
        }
        return osc.opt_type;
    }