How to Decompress Files from a ZIP file in Java

1. Overview

In previous article, we show you how to compress files to a zip file format. In this article we will show you how to unzip it. The example from this article uses try-with-resources Statement to auto close the resources and compiled and executed on JDK 8 and later.

2. Decompress Files from a ZIP file Example

1. Read ZIP file with “ZipInputStream”

ZipInputStream zis = new ZipInputStream(new FileInputStream(zipFile))

2. Get the files to “ZipEntry” and output it to “FileOutputStream“

FileOutputStream fos = new FileOutputStream(newFile)

In this example, it will read a ZIP file from “C:\Project_Work\samples\dest_sample.zip“, and decompress all zipped files to “C:\Project_Work\samples\outputzip” folder.

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

/**
 * This Java program demonstartes that how to decompress files from zip.
 * @author javaguides.net
 *
 */
public class DecompressZipExample {
 List<String> fileList;
 private static final String INPUT_ZIP_FILE = "C:\\Project_Work\\samples\\dest_sample.zip";
 private static final String OUTPUT_FOLDER = "C:\\Project_Work\\samples\\outputzip";

 public static void main(String[] args) {
  DecompressZipExample unZip = new DecompressZipExample();
  unZip.unZipIt(INPUT_ZIP_FILE, OUTPUT_FOLDER);
 }

 /**
  * Unzip it
  * 
  * @param zipFile
  *            input zip file
  * @param output
  *            zip file output folder
  */
 public void unZipIt(String zipFile, String outputFolder) {

  byte[] buffer = new byte[1024];

  File folder = new File(OUTPUT_FOLDER);
  if (!folder.exists()) {
   folder.mkdir();
  }

  try (ZipInputStream zis = new ZipInputStream(new FileInputStream(zipFile))) {
   // get the zipped file list entry
   ZipEntry ze = zis.getNextEntry();

   while (ze != null) {

    String fileName = ze.getName();
    File newFile = new File(outputFolder + File.separator + fileName);

    System.out.println("file unzip : " + newFile.getAbsoluteFile());

    // create all non exists folders
    // else you will hit FileNotFoundException for compressed folder
    new File(newFile.getParent()).mkdirs();

    try (FileOutputStream fos = new FileOutputStream(newFile)) {
     int len;
     while ((len = zis.read(buffer)) > 0) {
      fos.write(buffer, 0, len);
     }
    }
    ze = zis.getNextEntry();
   }

   zis.closeEntry();
   zis.close();

   System.out.println("Done");

  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
}

Output:

file unzip : C:\Project_Work\samples\outputzip\sample.txt
file unzip : C:\Project_Work\samples\outputzip\sample1.txt
file unzip : C:\Project_Work\samples\outputzip\sample2.txt
Done

3. References

https://docs.oracle.com/javase/8/docs/api/java/io/FileOutputStream.html
https://docs.oracle.com/javase/8/docs/api/java/util/zip/ZipEntry.html
https://docs.oracle.com/javase/8/docs/api/java/io/FileInputStream.html
https://docs.oracle.com/javase/8/docs/api/index.html?java/util/zip/ZipOutputStream.html
https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

The source code of this post is available on GitHub:How to Decompress Files from a ZIP file in Java