Short Notes on Java Archive(JAR) file

JAR:

The Java Archive (JAR) file format enables you to bundle multiple files into a single archive file. Typically a JAR file contains the class files and auxiliary resources associated with applets and applications

Advantages:

• Security, A jar file can be digitally signed enabling users to verify the signature and then grant the program security privileges.

• Decreased download time, since the archive is compressed it takes less time to download than it would to download each individual file.

• Package Versioning, A Jar file may contain vendor and version information about the files it contains.

• Portability, all Java Runtime Environments know how to handle Jar files.

Example:

1. Making javafile and compile that

   package amir;
   public class Hello
   {
   public static void main(String arg[])
   {
   System.out.println("Hello its form Hello.java inside amir package");
   }
   }
   

javac Hello.java

then amir directory have amir->Hello.java

->Hello.class

2. Creating mainclass file:
   mainclass contains below line
   Main-Class: amir.Hello

3. Making jar files:
   jar cmf mainclass myfirst.jar amir/Hello.class
   then u will get myfirst.jar

4. Viewing jar files:
   jar tf myfirst.jar
   then it will show as below
   META-INF/
   META-INF/MANIFEST.MF
   amir/Hello.class
   

5. Running jar file:
   java -jar myfirst.jar
   output:
   Hello its form Hello.java inside amir package