Zip and Unzip Files with Java

Introduction: The Java platform provides powerful API to work with the most popular compressed file format – zip format.

The ZIP API:

The java.util.zip package provides classes for working with zip file format.

The key classes in java.util.zip package are listed as following:

ZipInputStream: this is the main class which can be used for reading zip file and extracting files and directories (entries) within the archive. Here are some important usages of this class:

§  read a zip via its constructor ZipInputStream(FileInputStream)

§  read entries of files and directories via method getNextEntry()

§  read binary data of current entry via method read(byte)

§  close current entry via method closeEntry()

§  close the zip file via method close()

ZipEntry: this class represents an entry in the zip file. Each file or directory is represented as a ZipEntry object. Its method getName() returns a String which represents path of the file/directory.

 FileOutputStream class is used to write content of the current ZipEntry to a file on disk, via its method write(byte[] bytes, int offset, int length).

ZipOutputStream: this class allows writing files into a zip file. It accepts an OutputStream object in the constructor ZipOutputStream(OutputStream out); The putNextEntry() method allows to append a file at the end of the zip file.

JavaCode to create Zip File:

 For this example I created  “test” and  “zip” folders under c:\drive. I placed three .txt files under “test” folder. The following code creates a Zip file using these  three .txt files and place it at c:\test\zip\test.zip.

import java.io.File; 

import java.io.FileInputStream; 

import java.io.FileNotFoundException;

import java.io.FileOutputStream; 

import java.io.IOException; 

import java.util.zip.ZipEntry; 

import java.util.zip.ZipOutputStream; 

public class zipFile { 

public static void main(String[] args) { 

//source of files that need to be zipped

String[] textfiles = { "C:/test/test1.txt", "C:/test/test2.txt", "C:/test/test3.txt"}; 

//place to create a zip file

String zipFile = "C:/test/zip/test.zip"; 

try { 

       // create byte buffer 

       byte[] buffer = new byte[1024]; 

     

     //create FileOutputStream to write a file with specified file path and name

      FileOutputStream out = new FileOutputStream(zipFile); 

    //create ZipOutputStream from FileOutputStream to filter output stream in zip format

       ZipOutputStream zipout = new ZipOutputStream(out); 

       

      //loop through each file

       for (int i=0; i < textfiles.length; i++) { 

              //create a  new file instance for specified file 

               File srcFile = new File(textfiles[i]);

               System.out.println("Adding: "+srcFile.getName());  

             // create a FileInputStream to open a file

              FileInputStream in = new FileInputStream(srcFile); 

            // create a ZipEntry with file name and start writing to ZipOutputStream.

              zipout.putNextEntry(new ZipEntry(srcFile.getName())); 

               int length; 

              //read up to 1024 bytes from the file into an array of byte and write the data in current ZipEntry

               while ((length = in.read(buffer)) > 0) { 

                  zipout.write(buffer, 0, length); 

               } 

             //close zipEntry

              zipout.closeEntry(); 

              

              // close the InputStream 

              in.close(); 

             } 

          // close the ZipOutputStream 

          zipout.close(); 

          System.out.println("All files are zipeed to " + zipFile);

      } 

     catch (IOException ioe) { 

          System.out.println("Error creating zip file: " + ioe); 

      } 

   } 

   

 }

Output:

Adding: test1.txt

Adding: test2.txt

Adding: test3.txt

All files are zipeed to C:/test/zip/test.zip

Java Code to UnZip File:

I created a folder called “unzip” under c:\test. I used the zip file I created in previous example(c:\test\zip\test.zip) and unzipped the files to c:\test\unzip folder.

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.sql.Date;

import java.util.zip.ZipEntry;

import java.util.zip.ZipInputStream;

public class unzipFile {

           

            public static void main(String[] args)

            {

                       

            try {

            //zip file needs to be extracted

            String zipFile="c:/test/zip/test.zip";

            //destination folder where you need to unzip

            String dest="c:/test/unzip";

            //create InputStream object to open a file

            FileInputStream in=new FileInputStream(zipFile);

            //Create ZipInputStream object to read Zip file

            ZipInputStream zipin=new ZipInputStream(in);

            //each file/directory is represented as entry. Read entries of files/directories

            ZipEntry entry=zipin.getNextEntry();

            while(entry!=null)

            {

                        //file name

                        String entryName=entry.getName();

                        System.out.println("Extracting: " + entryName + " To " + dest);

                        //extracted file location & name

                        File extractedFile=new File(dest+ File.separator + entryName);

                       

                       

                       

                        //extractedFile.getParentFile().mkdirs();

                        //create FileOutputStream Object

                        FileOutputStream out=new FileOutputStream(extractedFile);

                        int len;

                        byte [] buffer=new byte[1024];

                        while((len=zipin.read(buffer)) >0)

                        {

                                    //write content of current entry to a file

                                    out.write(buffer,0,len);

                        }

                        out.close();

                        System.out.println("extracted:" + extractedFile);

                        entry=zipin.getNextEntry();

                       

            }

               zipin.closeEntry();

               zipin.close();

               System.out.println("Unzipping is complete");

            }

            catch(IOException io)

            {

                        io.printStackTrace();

            }

           

}

}

Output:

Extracting: test1.txt To c:/test/unzip

extracted:c:\test\unzip\test1.txt

Extracting: test2.txt To c:/test/unzip

extracted:c:\test\unzip\test2.txt

Extracting: test3.txt To c:/test/unzip

extracted:c:\test\unzip\test3.txt

Unzipping is complete