This chapter introduces Java application programming 
We begin with examples of programs that display output 
messages on the screen We then present a program that
obtains inputs two numbers from a user calculates 
their sum and displays the result You'll learn how to 
instruct the computer to perform arithmetic calculations 
and save their results for later use The last example 
demonstrates how to make decisions The application 
compares two numbers then displays messages that show 
the comparison results You'll use the JDK commandline 
tools to compile and run this chapter's programs