What you want to do is add libraries to your project build path (the class path that will be used during compilation). In Eclipse, you can do this by right-clicking on your project and selecting Properties(or clicking [Alt]+[Enter]when the project is selected in Project Explorer, Navigatoror Package Explorer), and then Java Build Pathfrom the sidebar and tab Librarieswhere you can add the JAR.
Note that the difference between Add JARsand External JARsis that it External JARswill add an external dependency to your project, since the absolute JAR path in your file system will be included in your project configuration. With, Add JARsyou can select a JAR from your workspace.
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