Ajd chapter6

ajd chapter 6
In future, instead of doing this, try writing a unit test. It makes it easier to read in future as you don't have to run it to see what it does (see my [StackTest.java](https://github.com/SandyThomson/Java-Training/blob/sdt_chapter6/test/com/selftest/StackTest.java) for an example).

Import JUnit4 into your classpath (it comes with Eclipse), and then you can