Christopher Schultz wrote:
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David,
On 5/19/2009 3:04 PM, David kerber wrote:
I have a section of code in a frequently-called (~3.5 million times
per day) servlet where I had to process based on a parameter that
could take one of 6 different single-character string values. I had
been using an if .. else if construct. Then I discovered that java
1.5 allowed constructing a switch on strings. So I did some speed
testing of a standalone java class that compared the 6-option switch
that vs my 6-step if/elseif.
I'd be interested to see what the bytecode looks like. Javac compiles
switch statements (using primitives) to one of two bytecodes:
lookupswitch or tableswitch. If you can get the compiler to generate a
tableswitch, your performance will increase dramatically due to the way
the bytecode works.
See
http://java.sun.com/docs/books/jvms/second_edition/html/Compiling.doc.html#14942
for more information on these bytecodes.
Interesting. From that description, depending on how sparse is
"sparse", there's probably a good chance I'm getting a tableswitch. Can
you point me to a byte code interpreter so I could look at this? Or I
could just send you the .class file of my test class if you'd prefer.
D
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