Strings

1. 方法:

   1. char charAt(int index)
      returns char value for the particular index

   2. int length()
      returns string length

   3. String substring(int beginIndex)
      returns substring for given begin index

   4. String substring(int beginIndex, int endIndex)
      returns substring for given begin index and end index

   5. String[] split(String regex)
      returns splitted string matching regex

   6. int indexOf(int ch)
      returns specified char value index