Java Programming:Oracle JDK not Working.

[Gatts]

Hello everyone.
 Im a total newbie to ubuntu and wanna use it to learn Java Programming. I have recently upgraded to Ubuntu 11.10 from 11.04.
Then i installed Oracle JDK 7.However when i try to compile a Java Program,it does not work though the JDK is properly installed.
So i need the problem solved so than to i can continue to learn Java.
 I have included details for the javac version,java version and what i see when i try to compile the problem.
  Please help me fix it.All the help is welcome.

javac -version
                      javac 1.7.0_02
 java -version
                      java version "1.7.0_147-icedtea"

OpenJDK Runtime Environment (IcedTea7 2.0) (7~b147-2.0-0ubuntu0.11.10.1)

OpenJDK Server VM (build 21.0-b17, mixed mode)

javac hello.java

javac: file not found: hello.java

Usage: javac <options> <source files>

use -help for a list of possible options