How to Zip Files in Java

This post shows how you can zip files in Java. Using the options given here you can zip a single file or more than one file by specifying all those files.

Zip a file in Java

To zip files in Java there are two options-

  1. Using ZipOutputStream and ZipEntry classes residing in java.util.zip package.
  2. Using the Zip File System Provider– The zip file system provider treats a zip or JAR file as a file system and provides the ability to manipulate the contents of the file. The zip file system provider was introduced in the JDK 7 release.

Want to zip a folder, check this post How to Zip a Folder in Java

Zipping single fie in Java using ZipOutputStream

The steps for zipping a file using ZipOutputStream are as follows-

  • Create an InputStream for reading the source file.
  • Create an OutputStream for the zip file and wrap it in a ZipOutputStream object.
  • Create a ZipEntry instance for the source file and add it to the ZipOutputStream.
  • Read data from the source file and write it to the ZIP file.
  • Close the streams.
public class ZipFile {
  public static void main(String[] args) {
    // source file
    String fileName = "F:\\knpcode\\links.txt";
    File file = new File(fileName);
    //Creating zipfile name from fileName by 
    // truncating .txt and appending .zip
    String zipFilename = fileName.substring(0, fileName.indexOf('.')) + ".zip";
    File zipFile = new File(zipFilename);
    zipFile(file, zipFile);
  }
	
  // Method to zip file
  private static void zipFile(File file, File zippedFile){
    final int BUFFER = 1024;
    ZipOutputStream zos = null;
    BufferedInputStream bis = null;
    try{
      FileInputStream fis = new FileInputStream(file);
      bis = new BufferedInputStream(fis, BUFFER);          
      // Creating ZipOutputStream for writing to zip file
      FileOutputStream fos = new FileOutputStream(zippedFile);
      zos = new ZipOutputStream(fos);
      // Each file in the zipped archive is represented by a ZipEntry 
      // Only source file name is needed 
      ZipEntry ze = new ZipEntry(file.getName());        
      zos.putNextEntry(ze);
      byte data[] = new byte[BUFFER];
      int count;
      while((count = bis.read(data, 0, BUFFER)) != -1) {
        zos.write(data, 0, count);
      }                     
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }finally{
      try {
        zos.close();
        bis.close();
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }  
    }
  }
}

Zipping single fie in Java using Zip File System Provider

You can use the factory methods of the java.nio.file.FileSystems class to create a new zip file system or to obtain a reference to an existing zip file system.
You can create a zip file system by specifying the path of the zip or JAR file in following way-

URI uri = URI.create(“jar:file:/PATH/TO/ZIPFILE”);
FileSystem fs = FileSystems.newFileSystem(uri, env);

public class ZipFile {
  public static void main(String[] args) {
    // source file
    String fileName = "F:/knpcode/links.txt";
    //Creating zipfile name from fileName by 
    // truncating .txt and appending .zip
    String zipFilename = fileName.substring(0, fileName.indexOf('.')) + ".zip";
    
    zipFile(fileName, zipFilename);
  }

  private static void zipFile(String file, String zippedFile){
    Map<String, String> env = new HashMap<>(); 
    env.put("create", "true");
    // locate file system by using the syntax 
    // defined in java.net.JarURLConnection
    URI uri = URI.create("jar:file:/" + zippedFile);
    try (FileSystem zipfs = FileSystems.newFileSystem(uri.normalize(), env)) {
      Path sourceFile = Paths.get(file);
      System.out.println("Name-- " + sourceFile.getFileName().toString());
      Path pathInZipfile = zipfs.getPath(sourceFile.getFileName().toString());          
      // copy a file into the zip file
      Files.copy(sourceFile, pathInZipfile, StandardCopyOption.REPLACE_EXISTING ); 
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } 
  }
}

Zipping multiple files in Java

Here is an example of zipping multiple files in Java using ZipOutputStream where each source file is added as a ZipEntry to the ZipOutputStream.

public class ZipFile {
  public static void main(String[] args) {
    try {
      // source files
      String file1 = "F:/knpcode/links.txt";
      String file2 = "F:/knpcode/Test/postend.txt";
      // Zipped file name
      String zipFilename = "F:/knpcode/result.zip";
      File zipFile = new File(zipFilename);
      // Creating ZipOutputStream for writing to zip file
      FileOutputStream fos  = new FileOutputStream(zipFile);			
      ZipOutputStream zos = new ZipOutputStream(fos);
      
      zipFile(file1, zos);
      zipFile(file2, zos);
      zos.close();
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
	
  // Method to zip file
  private static void zipFile(String fileName, ZipOutputStream zos) throws IOException{
  final int BUFFER = 1024;
  BufferedInputStream bis = null;
  try{
    File file = new File(fileName);
    FileInputStream fis = new FileInputStream(file);
    bis = new BufferedInputStream(fis, BUFFER);          

    // Each file in the zipped archive is represented by a ZipEntry 
    // Only source file name is needed 
    ZipEntry zipEntry = new ZipEntry(file.getName());        
    zos.putNextEntry(zipEntry);
    byte data[] = new byte[BUFFER];
    int count;
    while((count = bis.read(data, 0, BUFFER)) != -1) {
      zos.write(data, 0, count);
    }    
      zos.closeEntry();
    } finally{
      try {
        bis.close();
      } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }  
    }
  }
}

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