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In this chapter you learned about how a Java program is structured. You learned what the major parts of the Java source files are for. You were also introduced to variables. Variables allow the program to hold values while it processes data. Variables are very important to programming, and it is very important that you understand how they work.

You learned the difference between strings and numbers. You saw that strings hold text data and numbers can perform mathematical operations. You can also convert between Strings and numbers. Java supports many different types of variables. Some can hold bigger numbers than others.

You learned about comments and how they can make your program easier to understand. Java supports both single-line and multi-line comments. Single line comments begin with a //. Multi line comments are between a beginning /* and an ending */.