introduction

• JDK 1.8
  

  split function

  notice that the split function takes a regular expression as an argument. The split function is defined as:

  /**
   * Splits this string around matches of the given <a
   * href="../util/regex/Pattern.html#sum">regular expression</a>.
   *
   * <p> This method works as if by invoking the two-argument {@link
   * #split(String, int) split} method with the given expression and a limit
   * argument of zero.  Trailing empty strings are therefore not included in
   * the resulting array.
   *
   * <p> The string {@code "boo:and:foo"}, for example, yields the following
   * results with these expressions:
   *
   * <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
   * <tr>
   *  <th>Regex</th>
   *  <th>Result</th>
   * </tr>
   * <tr><td align=center>:</td>
   *     <td>{@code { "boo", "and", "foo" }}</td></tr>
   * <tr><td align=center>o</td>
   *     <td>{@code { "b", "", ":and:f" }}</td></tr>
   * </table></blockquote>
   *
   *
   * @param  regex
   *         the delimiting regular expression
   *
   * @return  the array of strings computed by splitting this string
   *          around matches of the given regular expression
   *
   * @throws  PatternSyntaxException
   *          if the regular expression's syntax is invalid
   *
   * @see java.util.regex.Pattern
   *
   * @since 1.4
   * @spec JSR-51
   */
  public String[] split(String regex) { ... }
  

  special symbol processing

  The

  split function takes a regular expression as an argument, so special processing is required when the special symbol of the regular expression is used as a delimiter.

  For example, . is a wildcard in regular expressions, and matches any single character except for line breaks (\n, \r).

  can be handled in two ways for special symbols:

  • escaped. For example, \.
  • put it in brackets. For example, the [.]
    Example

    String[] s1 = "a.b.c".split("\\.");
    System.out.println(Arrays.asList(s1)); //[a, b, c]
    
    String[] s2 = "a.b.c".split("[.]");
    System.out.println(Arrays.asList(s2)); //[a, b, c]
    

    Reference

    https://www.runoob.com/regexp/regexp-metachar.html