Java Reference
In-Depth Information
each with unique types of parameters. For example, the
String
class has many
different constructors, including one which constructs a new
String
from a
different
String
and another that constructs a new
String
from an array
of bytes.
String strbystr = new String(oldstr);
String strbyarr = new String(myByteArray);
3.2.2.2
One of the most commonly used classes is the
String
class. It comes already
defined as part of Java and has some special syntax for initialization which
makes it look familiar. Whereas other objects need a
new
keyword and a con-
structor call, a
String
object can be created and initialized with the intuitive
double quotes, as in:
Strings
String xyz="this is the stringtext";
The compiler also makes a special allowance for
String
s with respect to
the plus sign (
+
). It can be used to concatenate two
String
s into a third, new
String
.
String phrase = "That is"
String fullsent = phrase + " all.";
It is worth noting that
String
s do not change—they are
immutable
.
When you assign a
String
the value of one
String
plus another, there's a lot
of
String
object creation going on behind the scenes. If you need to do a lot
of concatenation of
String
s, say inside loops, then you should look into the
use of the
StringBuffer
object. See Appendix A of
Thinking in Java
, 3rd ed.,
the section titled Overloading “+” and the
StringBuffer
, for a full discussion
of the tradeoffs here.
There are a variety of methods for
String
—ones that will let you make
substrings, search for substrings at the start or end or anywhere in the string,
or check for equality of two strings.
Table 3.2 shows some of the most useful methods associated with
String
objects.
