Java Security

Hello all,

I have problem with Jar File On Java Lenguage.
I has created the Program with Java and i has compile to Jar File.

but i have problem about this package.
i can extract the JAR file with winrar, and i found my class.
so i open my class file with java editor i get the .java file again.

why the java jar file can be DeCompiler again ?
can halp me the solution for this problem.

How to create the Java's JAR File can not be Decompiler ?

for your answer thank you vary mutch