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Language: Java
Expertise: Intermediate
Apr 9, 2020



Building the Right Environment to Support AI, Machine Learning and Deep Learning


Retrieving a File from a Jar File

A JAR file in Java is a compressed format and is used for packaging of the deliverables. At times, you may want to manipulate this file.

The example below indicates a scenario for this.

import java.util.jar.*;
import java.io.*;

public class RetrievingJarEntry
   public static void main(String args[])
      RetrievingJarEntry retrievingJarEntry = new RetrievingJarEntry();
   private void proceed()
      String sourceJarFile = "files/contacts.jar";
      String sourceFile = "2.txt";
      String destFile = "files/new2.txt";
         JarFile jarFile = new JarFile(sourceJarFile);
         JarEntry jarEntry = jarFile.getJarEntry(sourceFile);
         System.out.println("Found entry: " + jarEntry);
         if ( jarEntry != null)
            //Getting the jarEntry into the inputStream
            InputStream inputStream = jarFile.getInputStream(jarEntry); 
            //Creating a output stream to a new file of our choice
            FileOutputStream fileOutputStream = new java.io.FileOutputStream(destFile);
            System.out.println("Attempting to create file: " + destFile);
            while (inputStream.available()  0) 
            System.out.println("Created file: " + destFile);
      }catch(IOException ioe)
         System.out.println("Exception: " + ioe);


Expected output:

[root@mypc]# java RetrievingJarEntry
Found entry: 2.txt
Attempting to create file: files/new2.txt
Created file: files/new2.txt


Please note: You have to create a folder with the name files and a jar file contacts.jar that has files 1.txt, 2.txt and 3.txt.

M S Sridhar
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