// compression/ZipCompress.java
// (c)2017 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);
 }
 }
}