Java Reference
In-Depth Information
hope) your web site to be sufficiently busy so that doing this efficiently will make a differen-
ce. There are two ways of thinking about this:
▪ Theory A: This string concatenation is inefficient.
▪ Theory B: String concatenation doesn't matter;
println()
is inefficient, too.
A proponent of Theory A might say that because
println()
just puts stuff into a buffer, it is
very fast and that string concatenation is the expensive part.
How to decide between Theory A and Theory B? Assume you are willing to write a simple
test program that tests both theories. Let's just write a simple program both ways and time it.
Example 23-8
is the timing program for Theory A.
Example 23-8. StringPrintA.java
public
public class
class
StringPrintA
StringPrintA
{
public
public static
void
main
(
String
[]
argv
) {
Object o
=
"Hello World"
;
for
static
void
for
(
int
int
i
=
0
;
i
<
100000
;
i
++) {
System
.
out
.
println
(
"<p><b>"
+
o
.
toString
() +
"</b></p>"
);
}
}
}
StringPrintAA
(in the
javasrc
repo but not printed here) is the same but explicitly uses a
StringBuilder
for the string concatenation.
Example 23-9
is the tester for Theory B.
Example 23-9. StringPrintB.java
public
public class
class
StringPrintB
StringPrintB
{
public
public static
void
main
(
String
[]
argv
) {
Object o
=
"Hello World"
;
for
static
void
for
(
int
int
i
=
0
;
i
<
100000
;
i
++) {
System
.
out
.
print
(
"<p><b>"
);
System
.
out
.
print
(
o
.
toString
());
System
.
out
.
print
(
"</b></p>"
);
System
.
out
.
println
();
}
}
}
