Java Reference
In-Depth Information
13.1. Character Sequences
As described in "
Character Set
"
on page
161
,
the Java programming lan-
guage represents text consisting of Unicode characters as sequences of
char
values using the
UTF
-16 encoding format. The
String
class defines
objects that represent such character sequences. More generally, the
java.lang.CharSequence
interface is implemented by any class that rep-
resents such a character sequencethis includes the
String
,
StringBuilder
,
and
StringBuffer
classes described in this chapter, together with the
java.nio.CharBuffer
class that is used for performing I/O.
The
CharSequence
interface is simple, defining only four methods:
public char
charAt(int index)
Returns the
char
in this sequence at the given
index
. Sequences
are indexed from zero to
length()-1
(just as arrays are in-
dexed). As this is a
UTF
-16 sequence of characters, the re-
turned value may be an actual character or a value that is part
of a surrogate pair. If the index is negative or not less than
the length of the sequence, then an
IndexOutOfBoundsException
is thrown.
public int
length()
Returns the length of this character sequence.
public CharSequence
subSequence(int start, int end)
Returns a new
CharSequence
that contains the
char
values in this
sequence consisting of
charAt(start)
through to
charAt(end-1)
.
If
start
is less than
end
or if use of either value would try to
index outside this sequence, then an
IndexOutOfBoundsException
is thrown. Be careful to ensure that the specified range doesn't
split any surrogate pairs.
