modify a file that is inside a jar [closed]

Because a .jar file is considered a compressed file similar to a .zip, you can use the zip package provided by Java:

  

Provides classes to read and write the standard ZIP and GZIP file formats.

link

  

This example contains two methods:

• Write (Enter the file fichero.jar % of the file archivo.txt )

• Read (Read the name of the files within fichero.jar )

  public class Clase {
  
  public static void main(String[] args) throws FileNotFoundException, IOException {
  
      Escribir();
      Leer();
  
  }
  
  public static void Escribir() throws IOException {
      ZipOutputStream os = new ZipOutputStream(new FileOutputStream("fichero.jar"));
  
      os.setLevel(Deflater.DEFAULT_COMPRESSION);
      os.setMethod(Deflater.DEFLATED);
  
      ZipEntry entrada = new ZipEntry("archivo.txt");
      os.putNextEntry(entrada);
  
      FileInputStream fis = new FileInputStream("archivo.txt");
      byte[] buffer = new byte[1024];
      int leido = 0;
      while (0 < (leido = fis.read(buffer))) {
          os.write(buffer, 0, leido);
      }
  
      fis.close();
      os.closeEntry();
  
      os.close();
  }
  
  public static void Leer() throws IOException {
  
      @SuppressWarnings("resource")
      ZipInputStream zis = new ZipInputStream(new FileInputStream("fichero.jar"));
  
      ZipEntry entrada;
      while (null != (entrada = zis.getNextEntry())) {
          System.out.println(entrada.getName());
  
          FileOutputStream fos = new FileOutputStream(entrada.getName());
          int leido;
          byte[] buffer = new byte[1024];
          while (0 < (leido = zis.read(buffer))) {
              fos.write(buffer, 0, leido);
          }
          fos.close();
          zis.closeEntry();
      }
  
  }
  

  }

  

With this class, you may be able to read and modify the .txt files you need. Feel free to make the adjustments you consider relevant.