The String and StringBuffer Classes |
String
s and StringBuffer
s
The bold line in thereverseIt
method creates aStringBuffer
nameddest
whose initial length is the same assource
.The codeclass ReverseString { public static String reverseIt(String source) { int i, len = source.length(); StringBuffer dest = new StringBuffer(len); for (i = (len - 1); i >= 0; i--) { dest.append(source.charAt(i)); } return dest.toString(); } }StringBuffer dest
declares to the compiler thatdest
will be used to refer to an object whose type isStringBuffer
, thenew
operator allocates memory for a new object, andStringBuffer(len)
initializes the object. These three steps--declaration, instantiation, and initialization--are described in Creating Objects.Creating a
String
ManyString
s are created from string literals. When the compiler encounters a series of characers enclosed in double quotes, it creates aString
object whose value is the text that appeared between the quotes. When the compiler encounters the following string literal, it creates aString
object whose value isGobbledy gook.
You can also create"Gobbledy gook."String
objects as you would any other Java object: using thenew
keyword.new String("Gobbledy gook.");Creating a
StringBuffer
The constructor method used byreverseIt
to initialize thedest
requires an integer argument indicating the initial size of the newStringBuffer
.StringBuffer(int length)reverseIt
could have usedStringBuffer
's default constructor that leaves the buffer's length undetermined until a later time. However, it's more efficient to specify the length of the buffer if you know it, instead of allocating more memory every time you append a character to the buffer.
The String and StringBuffer Classes |