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Packages

Packages. Tonga Institute of Higher Education. Pre-Built Objects and Methods. Method Name. Java has many pre-built objects for us to use. Doorknob analogy We want to add a doorknob to a door. We could make our own. But it’s easier to use a pre-built doorknob.

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Packages

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  1. Packages Tonga Institute of Higher Education

  2. Pre-Built Objects and Methods Method Name • Java has many pre-built objects for us to use. • Doorknob analogy • We want to add a doorknob to a door. • We could make our own. • But it’s easier to use a pre-built doorknob. • We still need to do work to add the doorknob to our door. • You can find a list of pre-built objects in the Java Developer’s Kit documentation. System.out.println("We Miss Dave!"); Package Parameter

  3. Demonstration Java API Documentation

  4. Organizing Classes • Java comes with over 2,700 different classes for doing different things. • Sun needed a way to organize the classes into groups, they decided to use packages. • A package is a group of related classes.

  5. java awt lang security geom image ref reflect acl spec event Packages • Java contains 140 different packages. • These packages are arranged hierarchically (packages inside of packages).

  6. java awt lang security geom image ref reflect acl spec event Package Names • The name of the package is actually a list of names, separated by periods. java.awt.image;

  7. Using Packages • If you want to use a built-in Java class, first look it up in the Java Application Interface. (API) • You can find the Java API documentation on the course website page. • http://www.tihe.org/courses/it151 This is the API entry for the Graphics class. The package for this class is java.awt.

  8. Using Packages (cont.) • Once you know the package for a class, import it into your program. • To import all classes in a package, use the wild card (*). import java.awt.Graphics; import java.awt.*;

  9. Case Study: Problem • Michael wants to use the Socket class in his program for Networking. • Which package does he need to include in his program? • What is the line of code he needs to write?

  10. Case Study: Answer • Look up the Socket class in the Java API • Use the import command to include the package: or import java.net.Socket; import java.net.*;

  11. Defining a Package • If you want to make your own package to be used in other programs, define it. • Defining packages can lead to problems compiling your program. • If you have multiple files in your project, make sure they are all defined in the same package. package myprojects.helloworld;

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