Compress or zip directory recursively in java (example)

1. Given an input directory containing files and sub-directories.
2. We would like to compress or zip all files present in a input directory.
   • We will traverse input directory recursively to compress all files.
3. Java framework has provided couple of classes to zip a file(s).
   • ZipOutputStream: ZipOutputStream class implements an output stream filter for writing files in ZIP file format.
   • ZipEntry: ZipEntry class represents an entry of ZIP file.

1. Program flow: Zip input directory (sub-directories)

1. Suppose, we would like to zip input directory containing files and sub-directories.
2. We will traverse the input directory recursively and we will create a list of all files.
3. We will create output zip files using ZipOutputStream.
4. We will traverse list of files and compress each file.
   • Each compress file will be added to ZipOutputStream.
5. At the end of traversal, we will get zipped output file.

2. Code: compress input directory recursively – ZipOutputStream (java)

package org.learn;

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

public class ZipFilesInDirectoryRecursively {

    public static void main(String[] args) throws IOException {

        File inputDirectory = new File("C:\\InputDirectory");
        File outputZip = new File("C:\\output\\zipDirectory.zip");
        outputZip.getParentFile().mkdirs();

        List listFiles = new ArrayList();

        //Populate all files...iterate through directories/subdirectories...
        //recursively
        System.out.printf("1. Input directory %s has following files:\n",
                                                    inputDirectory.getCanonicalPath());
        listFiles(listFiles, inputDirectory);

        //Create zip output stream to zip files
        ZipOutputStream zipOutputStream = new ZipOutputStream(
                new FileOutputStream(outputZip));

        //Create zip files by recursively iterating through directories
        //and sub directories....
        System.out.println("\n2. Output Zipped file at location:"+outputZip.getCanonicalPath());
        createZipFile(listFiles, inputDirectory, zipOutputStream);
    }

    private static void createZipFile(List listFiles, File inputDirectory,
                                      ZipOutputStream zipOutputStream) throws IOException {

        for (File file : listFiles) {
            String filePath = file.getCanonicalPath();
            int lengthDirectoryPath = inputDirectory.getCanonicalPath().length();
            int lengthFilePath = file.getCanonicalPath().length();

            //Get path of files relative to input directory.
            String zipFilePath = filePath.substring(lengthDirectoryPath + 1, lengthFilePath);

            ZipEntry zipEntry = new ZipEntry(zipFilePath);
            zipOutputStream.putNextEntry(zipEntry);

            FileInputStream inputStream = new FileInputStream(file);
            byte[] bytes = new byte[1024];
            int length;
            while ((length = inputStream.read(bytes)) >= 0) {
                zipOutputStream.write(bytes, 0, length);
            }
            zipOutputStream.closeEntry();
            System.out.println("Zipped file:"+filePath);
        }
        zipOutputStream.close();
    }

    //Get list of all files recursively by iterating through sub directories
    private static List listFiles(List listFiles, File inputDirectory)
            throws IOException {

        File[] allFiles = inputDirectory.listFiles();
        for (File file : allFiles) {
            if (file.isDirectory()) {
                listFiles(listFiles, file);
            } else {
                System.out.println(file.getCanonicalPath());
                listFiles.add(file);
            }
        }
        return listFiles;
    }
}

3. Output – zipped input directory – ZipOutputStream in java

4. Output – zipped input directory – ZipOutputStream in java

1. Input directory C:\InputDirectory has following files:
C:\InputDirectory\Dir1\Dir11\Dir11_F1.txt
C:\InputDirectory\Dir1\Dir11\Dir11_F2.txt
C:\InputDirectory\Dir1\Dir1_F1.txt
C:\InputDirectory\Dir1\Dir1_F2.txt
C:\InputDirectory\Dir2\Dir21\Dir21_F1.txt
C:\InputDirectory\Dir2\Dir21\Dir21_F2.txt
C:\InputDirectory\Dir2\Dir2_F1.txt
C:\InputDirectory\Dir2\Dir2_F2.txt
C:\InputDirectory\FirstFile.txt
C:\InputDirectory\SecondFile.txt
C:\InputDirectory\ThirdFile.txt

2. Output Zipped file at location:C:\output\zipDirectory.zip
Zipped file:C:\InputDirectory\Dir1\Dir11\Dir11_F1.txt
Zipped file:C:\InputDirectory\Dir1\Dir11\Dir11_F2.txt
Zipped file:C:\InputDirectory\Dir1\Dir1_F1.txt
Zipped file:C:\InputDirectory\Dir1\Dir1_F2.txt
Zipped file:C:\InputDirectory\Dir2\Dir21\Dir21_F1.txt
Zipped file:C:\InputDirectory\Dir2\Dir21\Dir21_F2.txt
Zipped file:C:\InputDirectory\Dir2\Dir2_F1.txt
Zipped file:C:\InputDirectory\Dir2\Dir2_F2.txt
Zipped file:C:\InputDirectory\FirstFile.txt
Zipped file:C:\InputDirectory\SecondFile.txt
Zipped file:C:\InputDirectory\ThirdFile.txt