正常截取一段字符串，substring按照单个字节来进行截取，如果碰到包含汉字在内的字符串截取，就会截取不准确
比如：123汉字5678，按字符串长度长度为5，按getByte("GBK")则长度为7，此时substring(6, 7)想截取到6，截取就会不准确
private static String subStringByByte(String str, int beginIndex, int endIndex) {
if (beginIndex < 0) throw new StringIndexOutOfBoundsException(beginIndex);
if (beginIndex > endIndex) throw new StringIndexOutOfBoundsException(endIndex - beginIndex);
if (beginIndex == endIndex) return "";
int byteLength = 0;
String returnString = "";
for (int i = 0; byteLength < endIndex && i < str.length(); i++) {
char c = str.charAt(i);
byteLength += (31 < c && c < 128) ? 1 : 2;
if (byteLength > beginIndex)
returnString += c;
}
return returnString;
}
