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Advanced Java Programming

Using wildcards in generic programming

From the course: Advanced Java Programming

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  • Course details

    Want to get more out of the Java language and platform? In this platform- and framework-neutral course, instructor Bethan Palmer digs into some of the language’s more advanced features, helping you expand your programming skills as she equips you with techniques you can use when building applications anywhere Java is used: in web, mobile, and desktop applications. Bethan covers a variety of topics, including generics, working with the Collections Framework, and functional programming. Plus, learn about I/O in Java, working with files and directories, and structuring applications using the modular system available in Java.


    • Click here to view Bethan Palmer’s instructor page

      Bethan Palmer

      Software Developer and Java Champion

      Bethan Palmer is a developer who loves technology and has a master's degree in computer science.

      For her day job, Bethan is a Java programmer and the product manager for a Java PDF library at IDRsolutions. She gets to spend a lot of time writing and refactoring code, as well as deciding on product strategy and road maps.

      She also spends much of her time attending conferences and is a regular speaker at Oracle Code One and NetBeans Days. She manages and writes articles about Java, technology, the books she's reading, and conferences she's attending on the Java PDF blog.

    Skills covered in this course

  • Learn advanced Java programming

    - Wildcards in Java can be useful in a variety of different situations. A wildcard is essentially an unknown type, and can give you more flexibility when writing methods. In this example, I have four classes. There is a class called building, a class called office, which extends building, a class called house, which also extends the building class, and finally a Main class. In the main class, I have a method called printBuildings. That takes a list of buildings as a parameter, and prints them to the terminal. In the main method, I also have a list of offices and a list of houses. However, I cannot pass either of these lists into the printBuilding methods. Because the list of type office is not a subtype of a list of type building. And nor is a list of type house. When I try and do this, I get a compile time error. One solution would be to create a new method for each different subtype of building. But a quicker and simpler solution is to use wildcards. In the list of arguments in the…

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