OnJava8-Examples/compression/ZipCompress.java

// 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}
// {ValidateByHand}
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);
    }
  }
}