1. 'javac' is not recognized as an internal or external command, operable program or batch file

If you receive this error, it means that Windows is not able to find the compiler (javac). Here's one way to tell Windows where to find javac. Set the PATH as follows on Microsoft Windows:

1. Click Start -> Control Panel -> System on Windows XP or Start -> Settings -> Control Panel -> System on Windows 2000.
2. Click Advanced -> Environment Variables.
3. Add the location of bin folder of JDK installation for PATH in User Variables and System Variables. A typical value for PATH is:

C:\Program Files\Java\jdk<version>\bin

Please note:

- PATH environment variable is a series of directories separated by semi-colons ( and is not case sensitive. Microsoft Windows looks for programs in the PATH directories in order, from left to right.
- You should only have one bin directory for a JDK in the path at a time. Those following the first instance are ignored. If one is already present, update it to jdk<version>\bin.
- If you are not sure where to add the path, add it to the right end of the PATH in the User Variables.
- The new path takes effect in each new command window you open after setting the PATH variable.
Or another way would be to go into notepad, and type: PATH=C:\Program Files\Java\jdk<version>\bin

Save that as Autoexec.bat (or modify an existing one), log-off and log-on again, them the binary path will be set so that windows can call javac straight from the cmd prompt rather than having to type in the full path .