java中文字符串截取

/**
* author geksong <br/>
* function 中文字符串相关操作<br/>
**/
public class ChinaStringUtil {
/**
 * 判断字符是不是中文字符
 * @param c
 * @return
 */
public static boolean isChinese(char c) {
    int ascii = (int)c;
    if(ascii >= 0 && ascii <= 255)
        return false;
    return true;
}

/**
 * 获取字符串的字节长度,中文按2字节算
 * @param chstring
 * @return
 */
public static int length(String chstring) {
    int length = 0;
    if(null == chstring || chstring.equals("") || chstring.length() == 0)
        return 0;
    for(int i = 0; i < chstring.length(); i++) {
        char c = chstring.charAt(i);
        if(isChinese(c))
            length += 2;
        else
            length += 1;
    }
    return length;
}

/**
 * 字符串截取，支持中文
 * @param chstring
 * @param offset
 * @param length
 * @return
 */
public static String subChString(String chstring, int offset, int length) {
    if(null == chstring || chstring.equals("") || chstring.length() == 0)
        return chstring;
    int num = 0;
    int index = -1;
    StringBuffer sb = new StringBuffer();
    for(int i = 0; i < chstring.length(); i++) {
        char c = chstring.charAt(i);
        int move = 0;
        if(isChinese(c))
            move = 2;
        else
            move = 1;
        index += move;
        if(index >= offset) {
            sb.append(c);
            num += move;
        }
        if(num >= length)
            break;
    }
    return sb.toString();
}
}