有时候我们需要知道字符串有多少个字节，比如Oracle中保存内容是按字节的长度的，因为中文和因为是不同的，所以需要写一个工具类来获取。

/**
  * 根据指定的字节长度截取字符串
  * @param orignal : 原始字符串
  * @param count ： 要截取的字节长度
  * @return
  */
public static String substringByByteLength(String orignal, int count){
    if(orignal != null && !"".equals(orignal)){
        int tmp = count;
        try {
            orignal = new String(orignal.getBytes("GBK"),"GBK");
            System.out.println(orignal.getBytes("GBK").length);
            if(tmp > 0 && tmp < orignal.getBytes("GBK").length){
                System.out.println("截取前的值："+orignal);
                StringBuffer buff = new StringBuffer();
                char c;
                for(int i = 0; i < tmp; i++){
                    c = orignal.charAt(i);
                    if((buff.toString() + String.valueOf(c)).getBytes("GBK").length <= count ){
                        buff.append(c);
                    }
                    if(isChinese(c)){
                        --tmp; //遇到中文汉字，截取字节总数减1   
                    }
                }
                String str = buff.toString();
                System.out.println("截取后的值："+str);
                return str;
            }
            return orignal;
        } catch (UnsupportedEncodingException e) {
    e.printStackTrace();
        }
    }
    return "";
}
public static boolean isChinese(char ch) {
    //获取此字符的UniCodeBlock
    Character.UnicodeBlock ub = Character.UnicodeBlock.of(ch);
    //  GENERAL_PUNCTUATION 判断中文的“号  
    //  CJK_SYMBOLS_AND_PUNCTUATION 判断中文的。号  
    //  HALFWIDTH_AND_FULLWIDTH_FORMS 判断中文的，号 
    if (ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS || ub == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS|| ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_B|| ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION || ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS|| ub == Character.UnicodeBlock.GENERAL_PUNCTUATION) {
        return true;
    }
    return false;
}