OnJava8-Examples/compression/ZipCompress.java

// compression/ZipCompress.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
// Uses Zip compression to compress any
// number of files given on the command line.
// {Args: ZipCompress.java}
import java.util.zip.*;
import java.io.*;
import java.util.*;

public class ZipCompress {
  public static void main(String[] args)
  throws IOException {
    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());
    }
    // 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());
    }
    // 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
      }
    }
  }
}
/* Output: (Execute to see) */