Java Reference
In-Depth Information
ponding wrapper class. Each parsing method has its own rules about
the allowed format of the string, for example
Float.parseFloat
will accept
a floating-point literal of the form
"3.14f"
, whereas
Long.parseLong
will
not accept the string
"25L"
. These numeric parsing methods have two
overloaded forms: one that takes a numeric base between 2 and 32 in
addition to the string to parse; and one that takes only the string and
assumes base 10. These parsing methods will also reject the string if it
has characters representing the base of the number, such as
"0x12FE"
for a hexadecimal value, or
"\033"
for an octal value. However, the
In-
teger
and
Long
wrapper classes also provide a static
decode
method that
will parse a string that does include this base information. For the nu-
meric types, if the string does not represent a valid value of that type,
a
NumberFormatException
is thrown.
To convert a
String
to a
char
you simply extract the first
char
from the
String
.
Your classes can support string encoding and decoding by having an ap-
propriate
toString
method and a constructor that creates a new object
given the string description. The method
String.valueOf(Objectobj)
is
defined to return either
"null"
(if
obj
is
null
) or the result of
obj.toString
.
The
String
class provides enough overloads of
valueOf
that you can con-
vert any value of any type to a
String
by invoking
valueOf
.
13.2.6. Strings and
char
Arrays
A
String
maps to an array of
char
and vice versa. You often want to build
a string in a
char
array and then create a
String
object from the con-
tents. Assuming that the writable
StringBuilder
class (described later)
isn't adequate, several
String
methods and constructors help you con-
vert a
String
to an array of
char
, or convert an array of
char
to a
String
.
There are two constructors for creating a
String
from a
char
array:
public
String(char[] chars, int start, int count)
