// compression/ZipCompress.java

// (c)2021 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Uses Zip compression to compress any

// number of files given on the command line

// {java ZipCompress ZipCompress.java}

// {VisuallyInspectOutput}

import java.util.zip.*;

import java.io.*;

import java.util.*;

public class ZipCompress {

public static void main(String[] args) {

try(

FileOutputStream f =

new FileOutputStream("test.zip");

CheckedOutputStream csum =

new CheckedOutputStream(f, new Adler32());

ZipOutputStream zos = new ZipOutputStream(csum);

BufferedOutputStream out =

new BufferedOutputStream(zos)

) {

zos.setComment("A test of Java Zipping");

// No corresponding getComment(), though.

for(String arg : args) {

System.out.println("Writing file " + arg);

try(

InputStream in = new BufferedInputStream(

new FileInputStream(arg))

) {

zos.putNextEntry(new ZipEntry(arg));

int c;

while((c = in.read()) != -1)

out.write(c);

}

out.flush();

}

// Checksum valid only after the file is closed!

System.out.println(

"Checksum: " + csum.getChecksum().getValue());

} catch(IOException e) {

throw new RuntimeException(e);

}

// Now extract the files:

System.out.println("Reading file");

try(

FileInputStream fi =

new FileInputStream("test.zip");

CheckedInputStream csumi =

new CheckedInputStream(fi, new Adler32());

ZipInputStream in2 = new ZipInputStream(csumi);

BufferedInputStream bis =

new BufferedInputStream(in2)

) {

ZipEntry ze;

while((ze = in2.getNextEntry()) != null) {

System.out.println("Reading file " + ze);

int x;

while((x = bis.read()) != -1)

System.out.write(x);

}

if(args.length == 1)

System.out.println(

"Checksum: "+csumi.getChecksum().getValue());

} catch(IOException e) {

throw new RuntimeException(e);

}

// Alternative way to open and read Zip files:

try(

ZipFile zf = new ZipFile("test.zip")

) {

Enumeration e = zf.entries();

while(e.hasMoreElements()) {

ZipEntry ze2 = (ZipEntry)e.nextElement();

System.out.println("File: " + ze2);

// ... and extract the data as before

}

} catch(IOException e) {

throw new RuntimeException(e);

}

}

}