Just to clarify the most commont and annoying problem that newbie Java-developer faces is the inability to compile .java files on the fly from windows command line. So to fix this
- Open console (Windows-run "cmd")
- Type "set" - this will list all of windows global variables. We are interested in Path variables since it allows to run applications without specifying full path all the time - operating system simply tries all of these paths
- Now we'll append this path with path to Java Development Kit (don't confuse with Java Runtime Enviroment) and it should look like this:
C:\foo\bar\> set PATH=%PATH%;C:\j2sdk1.4.2_01\bin
C:\foo\bar\> javac Filename.java
Other ways you can do same thing is from GUI, but how you do it varies from OS — its Computer / Properties / Advanced settings in WindowsXP and Command panel / User Accounts / Change my enviroment variables in Vista