Zipping and Unzipping Files in Java

ZIP is a common file format that compresses one or more files into a single location. It reduces the file size and makes it easier to transport or store. A recipient can unzip (or extract) a ZIP file after transport and use the file in the original format.

1. Single Zip file

Let's see how we can zip one file in Java using the core Java libraries java.util.zip package.

ZipMultipleFiles.java

import java.io.File ;
import java.io.FileInputStream ;
import java.io.FileOutputStream ;
import java.io.IOException ;
import java.util.zip.ZipEntry ;
import java.util.zip.ZipOutputStream ;
public class ZipSingleFile {
    public static void main ( String [ ] args ) throws IOException {
        String SourceFile = " website.txt " ;
        FileOutputStream FoS = new FileOutputStream( " web.zip " ) ;
        ZipOutputStream zipOut = new ZipOutputStream( FoS ) ;
        File fileToZip = new File( SourceFile ) ;
        FileInputStream FiS = new FileInputStream( fileToZip ) ;
        ZipEntry zipEntry = new ZipEntry( fileToZip.getName( ) ) ;
        zipOut.putNextEntry( zipEntry ) ;
        byte[ ] bytes = new byte[ 1024 ] ;
        int length ;
        while( ( length = FiS.read( bytes ) ) >= 0 ) {
            zipOut.write( bytes, 0, length ) ;
        }
        zipOut.close( ) ;
        FiS.close( ) ;
        FoS.close( ) ;
    }
}

Output:

When we open the created zip file, we found the text file.

2. Multiple Zip Files

Let's see how we can zip multiple files in Java using the core java libraries java.util.zip package.

ZipMultipleFiles.java

import java.io.File ;
import java.io.FileInputStream ;
import java.io.FileOutputStream ;
import java.io.IOException ;
import java.util.Arrays ;
import java.util.List ;
import java.util.zip.ZipOutputStream ;
import java.util.zip.ZipEntry ;
public class ZipMultipleFiles {
    public static void main( String[ ] args ) throws IOException {
        List<String> srcFiles = Arrays.asList( " file1.txt ", " file2.txt " ) ;
        FileOutputStream FoS = new FileOutputStream( " files.zip " ) ;
        ZipOutputStream ZoS = new ZipOutputStream( FoS ) ;
        
        for( String srcFile : srcFiles ) {
            File fileToZip = new File( srcFile ) ;
            FileInputStream FiS = new FileInputStream( fileToZip ) ;
            ZipEntry zipEntry = new ZipEntry( fileToZip.getName( ) ) ;
            ZoS.putNextEntry( zipEntry ) ;

            byte[ ] bytes = new byte[ 1024 ] ;
            int length ;
            while( ( length = FiS.read( bytes ) ) >= 0 ) {
                ZoS.write( bytes, 0, length ) ;
            }
            FiS.close( ) ;
        }
        ZoS.close( ) ;
        FoS.close( ) ;
    }
}

Output:

Let's open the zip file.

3. Zip Directory

Let's see how we can zip a directory in Java using the core libraries of java.util.zip package.

ZipDirectory.java

import java.io.File ;
import java.io.FileInputStream ;
import java.io.FileOutputStream ;
import java.io.IOException ;
import java.util.zip.ZipOutputStream ;
import java.util.zip.ZipEntry ;
public class ZipDirectory {
    public static void main( String[ ] args ) throws IOException {
        String sourceFile = "zipFiles" ;
        FileOutputStream FoS = new FileOutputStream( " dirCompressed.zip " ) ;
        ZipOutputStream zipOut = new ZipOutputStream( FoS ) ;
        File fileToZip = new File( sourceFile ) ;

        zipFile( fileToZip, fileToZip.getName( ), zipOut ) ;
        zipOut.close( ) ;
        FoS.close( ) ;
    }
    private static void zipFile( File fileToZip, String fileName, ZipOutputStream zipOut ) throws IOException {
        if ( fileToZip.isHidden( ) ) {
            return ;
        }
        if ( fileToZip.isDirectory( ) ) {
            if (fileName.endsWith( " / " ) ) {
                zipOut.putNextEntry( new ZipEntry( fileName ) ) ;
                zipOut.closeEntry( ) ;
            } else {
                zipOut.putNextEntry( new ZipEntry( fileName + " / " ) ) ;
                zipOut.closeEntry( ) ;
            }
            File[ ] children = fileToZip.listFiles( ) ;
            for ( File childFile : children ) {
                zipFile( childFile, fileName + " / " + childFile.getName( ), zipOut ) ;
            }
            return ;
        }
        FileInputStream FiS = new FileInputStream( fileToZip ) ;
        ZipEntry zipEntry = new ZipEntry( fileName ) ;
        zipOut.putNextEntry( zipEntry ) ;
        byte[ ] bytes = new byte[ 1024 ] ;
        int length ;
        while ( ( length = FiS.read( bytes ) ) >= 0 ) {
            zipOut.write( bytes, 0, length ) ;
        }
        FiS.close( ) ;
    }
}

Output:

zipFiles contains following files:

4. Unzip a file

Let's see how we can unzip a file in Java using the core libraries of java.util.zip package.

Unzip.java

import java.io.File ;
import java.io.FileInputStream ;
import java.io.FileOutputStream ;
import java.io.IOException ;
import java.util.zip.* ;
public class Unzip {
    public static void main( String[ ] args ) {
        String zipFilePath = " /Users/YuktaMalhotra/src/unzip/compressed.zip " ;
        String destDir = " /Users/YuktaMalhotra/src " ;
        unzipfile( zipFilePath, destDir ) ;
    }
    private static void unzipfile( String zipFilePath, String destDir ) {
        File dir = new File( destDir ) ;
        // creating an output directory if it doesn't exist already
        if( !dir.exists( ) ) dir.mkdirs( ) ;
        FileInputStream FiS ;
        // buffer to read and write data in the file
        byte[ ] buffer = new byte[ 1024 ] ;
        try {
            FiS = new FileInputStream( zipFilePath ) ;
            ZipInputStream ZiS = new ZipInputStream( FiS ) ;
            ZipEntry ZE = zis.getNextEntry( ) ;
            while( ZE != null ) {
                String fileName = ZE.getName( ) ;
                File newFile = new File( destDir + File.separator + filename ) ;
                System.out.println( " Unzipping to " + newFile.getAbsolutePath( ) ) ;
                // create directories for sub directories in zip
                new File( newFile.getParent( ) ).mkdirs( ) ;
                FileOutputStream FoS = new FileOutputStream( newFile ) ;
                int len ;
                while ( ( len = ZiS.read( buffer ) )  > 0 ) {
                fos.write( buffer, 0, len ) ;
                }
                FoS.close( ) ;
                // close this ZipEntry
                ZiS.closeEntry( ) ;
                ZE = ZiS.getNextEntry( ) ;
            }
            // close last ZipEntry
            ZiS.closeEntry( ) ;
            ZiS.close( ) ;
            FiS.close( ) ;
        } catch ( IOException e ) {
            e.printStackTrace( ) ;
        }
      }
}

Output: