To create the JAR file in Microsoft Windows we will need to go to the command prompt.

Put all the files that are to be archived in some directory , say c:\test ( say files are b.txt and a)

Go to start menu and select run program. Go to the path where the files are there, here to c:\test

Check where SDK is located in machine.  Check for the jar.exe in bin folder into SDK folder package name. It can be like C:\j2sdk1.4.1_05\bin. Type the path of jar as shown below. Then type the jar command as

jar options xxx.jar file_names

Here,  options here shown are
c -> to create an new archive
v -> It gives the verbose output on standard output. It will give whole details of all the file being added and how much they are deflated.
f -> it specifies the file name of the created JAR

xxx.jar means the name of jar file you want to give for e.g. test.jar

file_names are the input files that are to be archived. Since we want all the files to be archived we have given below the parameter as asterisk (*).

When you run the command you see the following output ( because of –v option)

The jar file test.jar in created in test directory itself.

To unjar  the jar file back to original files you just need to give the following command in the jar file directory, in this example c:\test

C:\java\j2re1.4.1_02\bin\jar -xvf test.jar

Where x is the option to extract files from archive and C:\java\j2re1.4.1_02\bin\ is the JDK installation path.