Java Reference
In-Depth Information
Let's review the following statement:
String localText = "Some text";
First, a
String
object containing the text “Some text” was created by the com-
piler. Then, the object reference variable
localText
was created and adjusted to ref-
erence that object. The compiler handles all this automatically because it treats
String
variables in a special way. Whenever the compiler sees a double quoted con-
stant, it will automatically make sure that a
String
object has been created.
The
String
class, part of the Java runtime, actually maintains a pool of
String
s
with unique values. So the first time the runtime sees a literal string or a string-val-
ued constant expression, the
String
class will check an internal pool of previously
created
String
s. If one is found, then that
String
will be used. Otherwise, a new
one will be created and added to the internal pool. In either case, the compiler will
make sure a
String
object is created for your program when you use the previously
mentioned syntax.
This runtime optimization helps conserve memory utilization and improve per-
formance for commonly used strings. However, in most cases you, as a Java devel-
oper, should not be concerned with, or code in a manner that is dependant on, these
details, since the
String
class encapsulates this optimization in proper OO fashion.
C
OMPARING
S
TRINGS
The base
Object
class contains many useful methods. Since the
String
class inherits
from
Object
, every
String
object you create will contain these methods as well. One
example is a method called
equals()
that will compare two
String
s for equality:
Return type
Method name
Parameter signature
boolean
equals
(Strings)
A Java statement can use this method to compare the text value in a
String
ob-
ject (such as
localText
) to some other
String
object:
if (localText.equals ("Some other text")) {
...
}
