General Java Questions IV

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 General Java Questions IV

 Q: I am looking for more efficient compression APIs esp. for *.doc and *.html

files.

I need some Java APIs wherein I can implement various compression algorithms. I

have already the GZIP compression technique shipped with JDK s java.util.zip

package. I am looking for more efficient compression APIs esp. for *.doc and *.html

files.

Answer: You often get better compression results for a large number of smaller files

by concatenating the uncompressed files and then compressing the result. That s

why tar.gz is often superior to zip for large numbers of html files (like API docs).

You will not get much better general purpose compression than Zip, at least not until

you have a specific class of data and know very much about its structure. Even then

you ll need some experience and time working on a better compression method.

You might want to take a look at this Java implementation of bzip2:

http://www.aftexsw.com/aftex/products/java/bzip/

It uses more CPU cycles and memory but typically compresses better

than zip.

Marco

 Q: I need to programmatically replace an entry in a zip file.

I could not quite get it using the ZipOutputStream because it simply creates a new

file and write only that entry for me. The rest of the original entries are gone. 

Does anyone have a solution for this?

Answer:

1) Read the file (myfile.properties) out of the original Zip Archive (original.zip)

2) Make your changes, write the file to the file system

3) Create a New Archive (originalNew.zip)

4) Write your edited file (myfile.properties) to originalNew.zip

5) loop through all the entries in the original Zip archive (original.zip),  adding them to

the new archive (originalNew.zip) EXCEPT for the file you are replacing

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