How to Unzip a File in Java

When you zip a file in Java there are different logic based on whether you are zipping a file or you are zipping a folder in Java where the whole directory structure is archived. But unzipping a file in Java doesn’t need such different functionalities. One Java program to unzip a file takes care of all the different functionalities.

Unzip a file – Java program

To unzip a file you need to follow the following steps-

Read the compressed file from the zipped archive. For that java.util.zip.ZipInputStream class is used.
From the ZipInputStream, zip entries for the files and directories are read using getNextEntry() method.
If the entry is for a directory then you just need to create the directory. If the entry is for file then read the content of the file and write it to the destination file.
Close the current entry using the closeEntry() method.
Once all the zip entries are iterated close the input and output streams.

public class UnzipFile {
  private static final int BUFFER = 2048;
  public static void main(String[] args) {
    final String SOURCE_ZIPDIR = "F:/knpcode/Parent.zip";
    // creating the destination dir using the zip file path
    // by truncating the ".zip" part
    String DESTINATION_DIR = SOURCE_ZIPDIR.substring(0, SOURCE_ZIPDIR.lastIndexOf('.'));
    //System.out.println("" + DESTINATION_DIR);
    extract(SOURCE_ZIPDIR, DESTINATION_DIR);
  }
	
  private static void extract(String source, String dest){
    try {
      File root = new File(dest);
      if(!root.exists()){
        root.mkdir();
      }
      BufferedOutputStream bos = null;
      // zipped input
      FileInputStream fis = new FileInputStream(source);
      ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
      ZipEntry entry;
      while((entry = zis.getNextEntry()) != null) {
        String fileName = entry.getName();
        File file = new File(dest + File.separator + fileName);
        if (!entry.isDirectory()) {
          extractFileContentFromArchive(file, zis);
        }
        else{
          if(!file.exists()){
            file.mkdirs();
          }
        }
        zis.closeEntry();
      }
      zis.close();
    } catch(Exception e) {
      e.printStackTrace();
    }
  }
	
  private static void extractFileContentFromArchive(File file, ZipInputStream zis) throws IOException{
    FileOutputStream fos = new FileOutputStream(file);
    BufferedOutputStream bos = new BufferedOutputStream(fos, BUFFER);
    int len = 0;
    byte data[] = new byte[BUFFER];
    while ((len = zis.read(data, 0, BUFFER)) != -1) {
      bos.write(data, 0, len);
    }
    bos.flush();
    bos.close();
  }
}

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KnpCode

February 5, 2024

How to Unzip a File in Java

Unzip a file – Java program

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