Using "Library" Classes and Methods 

In Unit 5, we spent our time developing and creating our own methods to streamline our programs. The methods that we create can be saved and used, when needed, in other programs to save time and eliminate repetition of efforts.

Now, not only do we have access to methods that we previously created, but we also have access to methods created by other programmers. The Java Development Kit (JDK) includes "built-in" classes and methods to make programming easier. The number and type of methods available depends upon the compiler being used. These methods that are already written and come with the JDK are referred to as "built-in" library methods.

Library methods are just like the methods that you create and are used in a similar fashion. The only difference is that the source code (definition) for a library method does NOT appear in your program. Your program will simply access these existing methods by importing the package where they are stored (if necessary) and by referencing the method by name.

There are dozens of libraries of methods available for your use. We will only be scratching the surface with our use of the most common library methods.

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