分割字符串到数组/替换字符串/返回指定字节长度的字符串/判断是否为浮点数，包括double和float/email判断/是否纯汉字判断/空白判断

package 字符串类;import java.util.*;import java.util.regex.Pattern;public class 某人编写的字符串工具类 {  /**   * 分割字符串到数组   *    * @param str String 原始字符串   * @param splitsign String 分隔符   * @return String[] 分割后的字符串数组   */  @SuppressWarnings("unchecked")  public static String[] split(String str, String splitsign) {    int index;    if (str == null || splitsign == null)      return null;    ArrayList al = new ArrayList();    while ((index = str.indexOf(splitsign)) != -1) {      al.add(str.substring(0, index));      str = str.substring(index + splitsign.length());    }    al.add(str);    return (String[]) al.toArray(new String[0]);  }  /**   * 替换字符串   *    * @param from String 原始字符串   * @param to String 目标字符串   * @param source String 母字符串   * @return String 替换后的字符串   */  public static String replace(String from, String to, String source) {    if (source == null || from == null || to == null)      return null;    StringBuffer bf = new StringBuffer("");    int index = -1;    while ((index = source.indexOf(from)) != -1) {      bf.append(source.substring(0, index) + to);      source = source.substring(index + from.length());      index = source.indexOf(from);    }    bf.append(source);    return bf.toString();  }  /**   * 替换字符串，能能够在HTML页面上直接显示(替换双引号和小于号)   *    * @param str String 原始字符串   * @return String 替换后的字符串   */  public static String htmlencode(String str) {    if (str == null) {      return null;    }    return replace("\"", """, replace("<", "<", str));  }  /**   * 替换字符串，将被编码的转换成原始码（替换成双引号和小于号）   *    * @param str String   * @return String   */  public static String htmldecode(String str) {    if (str == null) {      return null;    }    return replace(""", "\"", replace("<", "<", str));  }  private static final String _BR = "<br/>";  /**   * 在页面上直接显示文本内容，替换小于号，空格，回车，TAB   *    * @param str String 原始字符串   * @return String 替换后的字符串   */  public static String htmlshow(String str) {    if (str == null) {      return null;    }    str = replace("<", "<", str);    str = replace(" ", " ", str);    str = replace("\r\n", _BR, str);    str = replace("\n", _BR, str);    str = replace("\t", "    ", str);    return str;  }  /**   * 返回指定字节长度的字符串   *    * @param str String 字符串   * @param length int 指定长度   * @return String 返回的字符串   */  public static String toLength(String str, int length) {    if (str == null) {      return null;    }    if (length <= 0) {      return "";    }    try {      if (str.getBytes("GBK").length <= length) {        return str;      }    } catch (Exception ex) {    }    StringBuffer buff = new StringBuffer();    int index = 0;    char c;    length -= 3;    while (length > 0) {      c = str.charAt(index);      if (c < 128) {        length--;      } else {        length--;        length--;      }      buff.append(c);      index++;    }    buff.append("...");    return buff.toString();  }  /**   * 判断是否为整数   *    * @param str 传入的字符串   * @return 是整数返回true,否则返回false   */  public static boolean isInteger(String str) {    Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$");    return pattern.matcher(str).matches();  }  /**   * 判断是否为浮点数，包括double和float   *    * @param str 传入的字符串   * @return 是浮点数返回true,否则返回false   */  public static boolean isDouble(String str) {    Pattern pattern = Pattern.compile("^[-\\+]?[.\\d]*$");    return pattern.matcher(str).matches();  }  /**   * 判断输入的字符串是否符合Email样式.   *    * @param str 传入的字符串   * @return 是Email样式返回true,否则返回false   */  public static boolean isEmail(String str) {    Pattern pattern = Pattern.compile("^\\w+([-+.]\\w+)*@\\w+([-.]\\w+)*\\.\\w+([-.]\\w+)*$");    return pattern.matcher(str).matches();  }  /**   * 判断输入的字符串是否为纯汉字   *    * @param str 传入的字符窜   * @return 如果是纯汉字返回true,否则返回false   */  public static boolean isChinese(String str) {    Pattern pattern = Pattern.compile("[\u0391-\uFFE5]+$");    return pattern.matcher(str).matches();  }  /**   * 是否为空白,包括null和""   *    * @param str   * @return   */  public static boolean isBlank(String str) {    return str == null || str.trim().length() == 0;  }  /**   * 判断是否为质数   *    * @param x   * @return   */  public static boolean isPrime(int x) {    if (x <= 7) {      if (x == 2 || x == 3 || x == 5 || x == 7)        return true;    }    int c = 7;    if (x % 2 == 0)      return false;    if (x % 3 == 0)      return false;    if (x % 5 == 0)      return false;    int end = (int) Math.sqrt(x);    while (c <= end) {      if (x % c == 0) {        return false;      }      c += 4;      if (x % c == 0) {        return false;      }      c += 2;      if (x % c == 0) {        return false;      }      c += 4;      if (x % c == 0) {        return false;      }      c += 2;      if (x % c == 0) {        return false;      }      c += 4;      if (x % c == 0) {        return false;      }      c += 6;      if (x % c == 0) {        return false;      }      c += 2;      if (x % c == 0) {        return false;      }      c += 6;    }    return true;  }  public static void main(String[] args) {    String[] numbers = { "12345", "-12345", "123.45", "-123.45", ".12345", "-.12345", "a12345", "12345a", "123.a45" };    for (String str : numbers) {      System.out.println(str + "=" + isInteger(str) + " " + isDouble(str));    }    String[] emails = { "[e-mail]", "[e-mail]", "[e-mail]" };    for (String str : emails) {      System.out.println(str + "=" + isEmail(str));    }    String[] chineses = { "中国", "1中国", "中国1", "1中国2", "中1国" };    for (String str : chineses) {      System.out.println(str + "=" + isChinese(str));    }  }}