JSAPI HelloWorld NullPointerException Q

[Mahmoud Hadad]

hi all,
i have read the JSAPI programmer's Guide.anyway in the Synthesizers chapter there is a HelloWorld Example.When i try to run this example it compiles fine and in the run time it throws a NullPointerException and shows an error at the allocate().don't know i'm all new into this so i'm not using any implementations for JSAPI .
please advice what am i missing and what do i need to run the HelloWorld example.