解压文件 Unzip

 package com.scnu.zip;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
 
/**
 * UnZip -- print or unzip a JAR or PKZIP file using java.util.zip.

Command-line
 * version: extracts files.
 *
 * @author Ian Darwin, [e-mail] $Id: UnZip.java,v 1.7 2004/03/07
 *         17:40:35 ian Exp $
 */
public class UnZip {
  /** Constants for mode listing or mode extracting. */
  public static final int LIST = 0, EXTRACT = 1;
 
  /** Whether we are extracting or just printing TOC */
  protected int mode = LIST;
 
  /** The ZipFile that is used to read an archive */
  protected ZipFile zippy;
 
  /** The buffer for reading/writing the ZipFile data */
  protected byte[] b;
 
  /**
   * Simple main program, construct an UnZipper, process each .ZIP file

from
   * argv[] through that object.
   */
    //java Unzip zipfile.zip
  public static void main(String[] argv) {
    UnZip u = new UnZip();
 
    for (int i = 0; i < argv.length; i++) {
      if ("-x".equals(argv[i])) {
        u.setMode(EXTRACT);
        continue;
      }
      String candidate = argv[i];
      // System.err.println("Trying path " + candidate);
      if (candidate.endsWith(".zip") || candidate.endsWith(".jar"))
        u.unZip(candidate);
      else
        System.err.println("Not a zip file? " + candidate);
    }
    System.err.println("All done!");
  }
 
  /** Construct an UnZip object. Just allocate the buffer */
  UnZip() {
    b = new byte[8092];
  }
 
  /** Set the Mode (list, extract). */
  protected void setMode(int m) {
    if (m == LIST || m == EXTRACT)
      mode = m;
  }
 
  /** Cache of paths we've mkdir()ed. */
  protected SortedSet dirsMade;
 
  /** For a given Zip file, process each entry. */
  public void unZip(String fileName) {
    dirsMade = new TreeSet();
    try {
      zippy = new ZipFile(fileName);
      Enumeration all = zippy.entries();
      while (all.hasMoreElements()) {
        getFile((ZipEntry) all.nextElement());
      }
    } catch (IOException err) {
      System.err.println("IO Error: " + err);
      return;
    }
  }
 
  protected boolean warnedMkDir = false;
 
  /**
   * Process one file from the zip, given its name. Either print the

name, or
   * create the file on disk.
   */
  protected void getFile(ZipEntry e) throws IOException {
    String zipName = e.getName();
    switch (mode) {
    case EXTRACT:
      if (zipName.startsWith("/")) {
        if (!warnedMkDir)
          System.out.println("Ignoring absolute paths");
        warnedMkDir = true;
        zipName = zipName.substring(1);
      }
      // if a directory, just return. We mkdir for every file,
      // since some widely-used Zip creators don't put out
      // any directory entries, or put them in the wrong place.
      if (zipName.endsWith("/")) {
        return;
      }
      // Else must be a file; open the file for output
      // Get the directory part.
      int ix = zipName.lastIndexOf('/');
      if (ix > 0) {
        String dirName = zipName.substring(0, ix);
        if (!dirsMade.contains(dirName)) {
          File d = new File(dirName);
          // If it already exists as a dir, don't do anything
          if (!(d.exists() && d.isDirectory())) {
            // Try to create the directory, warn if it fails
            System.out.println("Creating Directory: " + dirName);
            if (!d.mkdirs()) {
              System.err.println("Warning: unable to mkdir "
                  + dirName);
            }
            dirsMade.add(dirName);
          }
        }
      }
      System.err.println("Creating " + zipName);
      FileOutputStream os = new FileOutputStream(zipName);
      InputStream is = zippy.getInputStream(e);
      int n = 0;
      while ((n = is.read(b)) > 0)
        os.write(b, 0, n);
      is.close();
      os.close();
      break;
    case LIST:
      // Not extracting, just list
      if (e.isDirectory()) {
        System.out.println("Directory " + zipName);
      } else {
        System.out.println("File " + zipName);
      }
      break;
    default:
      throw new IllegalStateException("mode value (" + mode + ") bad");
    }
  }
}
运行： java UnZip -x zipfile.zip