Java Reference
In-Depth Information
These objects belong to different classes. The
System.out
object belongs to the
class
PrintStream
. The
ÐHello, World!Ñ
object belongs to the class
String
. A class specifies the methods that you can apply to its objects.
You can use the
println
method with any object that belongs to the
PrintStream
class.
System.out
is one such object. It is possible to obtain other
objects of the
PrintStream
class. For example, you can construct a
PrintStream
object to send output to a file. However, we won't discuss files until
Chapter 11
.
A class defines the methods that you can apply to its objects.
Just as the
PrintStream
class provides methods such as
println
and
print
for
its objects, the
String
class provides methods that you can apply to
String
objects. One of them is the
length
method. The
length
method counts the number
of characters in a string. You can apply that method to any object of type
String
.
For example, the sequence of statements
String greeting = ÐHello, World!Ñ;
int n = greeting.length();
sets
n
to the number of characters in the
String
object
ÐHello, World!Ñ
. After
the instructions in the length method are executed,
n
is set to 13. (The quotation marks
are not part of the string, and the
length
method does not count them.)
The
length
methodȌunlike the
println
methodȌrequires no input inside the
parentheses. However, the
length
method yields an output, namely the character
count.
38
39
Figure 4
A Representation of Two
String
Objects
