When you work with Java, you work either within a vendor-specific development environment or within a general-purpose editor, with which you write your program, and a compiler, with which you translate your program into a form with which your Java virtual machine can work.
If you try to learn Java using a vendor-specific development environment, you learn a great deal about the vendor-specific development environment, but not enough about Java itself. Accordingly, this book introduces Java in the expectation that you will use a traditional editor and compiler.