How To Unzip File Using Java — Simple Tutorial

This tutorial is intended to show how Java programming language can be used to unzip a zip file. This program currently unzips a .zip extension.

Here are some features that I would like to highlight:

• You can hard code the zip file location and destination extraction location and then run the program.
• Alternately, you can pass these as an argument from the console.
• If you pass the parameters from the console, hard coded parameters will be discarded.
• This program does not maintain the folder structure.
• It unzips all the files into a given destination directory.
• You can tweak this program to unzip the file to the proper directory structures.
• This file unzipping tutorial uses standard Java API.
• You can download the source code here. You are free to modify and distribute this source code. Please honor my work by attributing back to my blog.

package com.kushal.utilities;

import java.io.*;
import java.util.*;
import java.util.zip.*;

public class MyUnzipUtil {

	public static final void main(String[] args) {
		/**
		 * Initialize the default parameters
		 */
		String zipFileName = "C:/myFolder/myZip.zip";
		String directoryToExtractTo = "C:/myFolder/unzipped/";

		/**
		 * Check if the arguments are passed from console.
		 * If so, we will discard the defalt parameters.
		 */

		if (args.length != 2) {
			System.err.println("Usage: MyUnzipUtil zipfile unzipLocation");
			System.err.println("...Using The Hardcoded Zip Location");
		} else {
			zipFileName = args[0];
			directoryToExtractTo = args[1];
		}

		/**
		 * Call the unzip method
		 */
		unzipMyZip(zipFileName, directoryToExtractTo);

	}

	/**
	 * This method
	 * --Reads an input stream
	 * --Writes the value to the output stream
	 * --Uses 1KB buffer.
	 */
	public static final void writeFile(InputStream in, OutputStream out)
			throws IOException {
		byte[] buffer = new byte[1024];
		int len;

		while ((len = in.read(buffer)) >= 0)
			out.write(buffer, 0, len);

		in.close();
		out.close();
	}

	public static void unzipMyZip(String zipFileName,
			String directoryToExtractTo) {
		Enumeration entriesEnum;
		ZipFile zipFile;
		try {
			zipFile = new ZipFile(zipFileName);
			entriesEnum = zipFile.entries();

			File directory= new File(directoryToExtractTo);

			/**
			 * Check if the directory to extract to exists
			 */
			if(!directory.exists())
			{
				/**
				 * If not, create a new one.
				 */
				new File(directoryToExtractTo).mkdir();
				System.err.println("...Directory Created -"+directoryToExtractTo);
			}
			while (entriesEnum.hasMoreElements()) {
				try {
					ZipEntry entry = (ZipEntry) entriesEnum.nextElement();

					if (entry.isDirectory()) {
						/**
						 * Currently not unzipping the directory structure.
						 * All the files will be unzipped in a Directory
						 *
						 **/
					} else {

						System.err.println("Extracting file: "
								+ entry.getName());
						/**
						 * The following logic will just extract the file name
						 * and discard the directory
						 */
						int index = 0;
						String name = entry.getName();
						index = entry.getName().lastIndexOf("/");
						if (index > 0 && index != name.length())
							name = entry.getName().substring(index + 1);

						System.out.println(name);

						writeFile(zipFile.getInputStream(entry),
								new BufferedOutputStream(new FileOutputStream(
										directoryToExtractTo + name)));
					}
				} catch (Exception e) {
					e.printStackTrace();
				}
			}

			zipFile.close();
		} catch (IOException ioe) {
			System.err.println("Some Exception Occurred:");
			ioe.printStackTrace();
			return;
		}
	}

}

Originally posted 2009-03-16 18:26:57.