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Java Compression and Decompression Tutorial with Examples

  1. Read write the zip file using java.util.zip
  2. Read write the jar file using java.util.jar
  3. Handle RAR file

1. Read write the zip file using java.util.zip

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To compress and decompress files, JDK give you package 'java.util.zip' with some class to do this.

Unfortunately, this library can not compress and decompress the popular formats like RAR, or 7zip. For the use of the format rar, 7zip, .. you need a different library. In this document I have to refer to the library to do this.
View a zip file is opened using WinRAR tool.
java.util.zip define files in the zip file is the ZipEntry.
ListZipEntriesDemo.java
package org.o7planning.tutorial.javaiozip;

import java.io.FileInputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

public class ListZipEntriesDemo {

	public static void main(String[] args) {
		String FILE_PATH = "C:/test/datas.zip"; 
		ZipInputStream zipIs = null;
		try {
			// Create ZipInputStream object to read zip file.
			zipIs = new ZipInputStream(new FileInputStream(FILE_PATH));

			ZipEntry entry = null;
			// Fetch entries (From Top to Bottom)
			while ((entry = zipIs.getNextEntry()) != null) {
				if (entry.isDirectory()) {
					System.out.print("Directory: ");
				} else {
					System.out.print("File: ");
				}
				System.out.println(entry.getName());
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				zipIs.close();
			} catch (Exception e) {
			}
		}
	} 
}
Results of running the example:
For example, unzip the zip file to a specific folder:
UnZipDemo.java
package org.o7planning.tutorial.javaiozip;

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

public class UnZipDemo { 
	public static void main(String[] args) {
		final String OUTPUT_FOLDER = "C:/output";
		String FILE_PATH = "C:/test/datas.zip";

		// Create Output folder if it does not exists.
		File folder = new File(OUTPUT_FOLDER);
		if (!folder.exists()) {
			folder.mkdirs();
		}
		// Create a buffer.
		byte[] buffer = new byte[1024];

		ZipInputStream zipIs = null;
		try {
			// Create ZipInputStream object to read a file from path.
			zipIs = new ZipInputStream(new FileInputStream(FILE_PATH));

			ZipEntry entry = null;
			// Read ever Entry (From top to bottom until the end)
			while ((entry = zipIs.getNextEntry()) != null) {
				String entryName = entry.getName();
				String outFileName = OUTPUT_FOLDER + File.separator + entryName;
				System.out.println("Unzip: " + outFileName);

				if (entry.isDirectory()) {
					// Make directories.
					new File(outFileName).mkdirs();
				} else {
					// Create Stream to write file.
					FileOutputStream fos = new FileOutputStream(outFileName);

					int len;
					// Read the data on the current entry.
					while ((len = zipIs.read(buffer)) > 0) {
						fos.write(buffer, 0, len);
					} 
					fos.close();
				} 
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				zipIs.close();
			} catch (Exception e) {
			}
		}
	} 
}
Results of running the example:
Compress a directory
ZipDirectory.java
package org.o7planning.tutorial.javaiozip;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

public class ZipDirectory { 
	public ZipDirectory() {

	} 
	// A method to Compress a directory.
	public void zipDirectory(File inputDir, File outputZipFile) {
		// Create parent directory for the output file.
		outputZipFile.getParentFile().mkdirs();

		String inputDirPath = inputDir.getAbsolutePath();
		byte[] buffer = new byte[1024];

		FileOutputStream fileOs = null;
		ZipOutputStream zipOs = null;
		try { 
			List<File> allFiles = this.listChildFiles(inputDir); 
			// Create ZipOutputStream object to write to the zip file
			fileOs = new FileOutputStream(outputZipFile);
			// 
			zipOs = new ZipOutputStream(fileOs);
			for (File file : allFiles) {
				String filePath = file.getAbsolutePath(); 
				System.out.println("Zipping " + filePath);
				// entryName: là một đường dẫn tương đối.
				String entryName = filePath.substring(inputDirPath.length() + 1);

				ZipEntry ze = new ZipEntry(entryName);
				// Put new entry into zip file.
				zipOs.putNextEntry(ze);
				// Read the file and write to ZipOutputStream.
				FileInputStream fileIs = new FileInputStream(filePath); 
				int len;
				while ((len = fileIs.read(buffer)) > 0) {
					zipOs.write(buffer, 0, len);
				}
				fileIs.close();
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			closeQuite(zipOs);
			closeQuite(fileOs);
		} 
	} 
	private void closeQuite(OutputStream out) {
		try {
			out.close();
		} catch (Exception e) {
		}
	} 
	// This method returns the list of files,
	// including the children, grandchildren files of the input folder.
	private List<File> listChildFiles(File dir) throws IOException {
		List<File> allFiles = new ArrayList<File>();

		File[] childFiles = dir.listFiles();
		for (File file : childFiles) {
			if (file.isFile()) {
				allFiles.add(file);
			} else {
				List<File> files = this.listChildFiles(file);
				allFiles.addAll(files);
			}
		}
		return allFiles;
	} 
	public static void main(String[] args) {
		ZipDirectory zipDir = new ZipDirectory(); 
		File inputDir = new File("C:/datas");
		File outputZipFile = new File("C:/output/datas.zip"); 
		zipDir.zipDirectory(inputDir, outputZipFile); 
	}
}
Results of running the example:

2. Read write the jar file using java.util.jar

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Basically read, write jar file is not any different than reading, writing Zip file.
  • JarInputStream extends from ZipInputStream, supports more methods to read MANIFEST information.
  • JarOutputStream extends from ZipOutputStream,supports more more method to write MANIFEST information
Example Manifest:
META-INF/MANIFEST.MF
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: RAPWorkbenchTutorial
Bundle-SymbolicName: RAPWorkbenchTutorial;singleton:=true
Bundle-Version: 1.0.0.qualifier
Bundle-Activator: rapworkbenchtutorial.Activator
Require-Bundle: org.eclipse.rap.ui;bundle-version="2.3.0",
org.apache.felix.gogo.command;bundle-version="0.10.0",
org.apache.felix.gogo.runtime;bundle-version="0.10.0",
org.apache.felix.gogo.shell;bundle-version="0.10.0",
org.eclipse.equinox.console;bundle-version="1.1.0",
org.eclipse.equinox.http.jetty;bundle-version="3.0.200",
org.eclipse.equinox.ds;bundle-version="1.4.200",
org.eclipse.rap.rwt.osgi;bundle-version="2.3.0",
org.eclipse.rap.design.example;bundle-version="2.3.0"
Bundle-RequiredExecutionEnvironment: JavaSE-1.7
Bundle-ActivationPolicy: lazy
For example, open a jar file with Winrar:
The entities in the jar file is considered to be the JarEntry.
A example of reading information MANIFEST file. Here are the contents of a simple Manifest file.
ReadJarFileDemo.java
package org.o7planning.tutorial.jar;

import java.io.FileInputStream;
import java.util.jar.Attributes;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
import java.util.jar.Manifest;

public class ReadJarFileDemo { 
	public static void main(String[] args) {
		String FILE_PATH = "C:/DevPrograms/Java/jdk1.7.0_45/lib/dt.jar"; 
		JarInputStream zipIs = null;
		try {
			// Create JarInputStream object to read jar file.
			zipIs = new JarInputStream(new FileInputStream(FILE_PATH)); 
			// Read manifest information:
			Manifest manifest = zipIs.getManifest();
			Attributes atts = manifest.getMainAttributes();
			String version = atts.getValue("Manifest-Version");
			String createdBy = atts.getValue("Created-By");
			System.out.println("Manifest-Version:" + version);
			System.out.println("Created-By:" + createdBy);
			System.out.println("========================"); 
			JarEntry entry = null;
			// Read ever Entry (From top to bottom until the end)
			while ((entry = zipIs.getNextJarEntry()) != null) {
				if (entry.isDirectory()) {
					System.out.print("Folder: ");
				} else {
					System.out.print("File: ");
				}
				System.out.println(entry.getName());
			} 
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				zipIs.close();
			} catch (Exception e) {
			}
		}
	} 
}
Results of running the example:

3. Handle RAR file

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To handle RAR file you need a open source code library. You can use one of the following libraries which is arranged in order of quality priority.
In this document I will guide you to use JUnRar
Download junrar:
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