Lesson - 15 : Eclipse IDE - Using JARs (libraries) in Eclipse

Adding a Java library to the project classpath:
You can store JAR files directly in your project, and add them to the classpath which the Java compiler of Eclipse is using. To manage the classpath for your Eclipse, right-click on your project and select Properties. Under Java Build Path ▸ Libraries you can review and change your current classpath as depicted in the following screenshot.

Using project dependencies:
You can define in Eclipse that a project is dependent on another project. If you do this, you can use its classes in the project defining the dependency. To do this select your project, right-click on it and select Properties. Select Java Build Path and the Projects tab.

Attach source code to a Java library:
You can open any class by positioning the cursor on the class in an editor and pressing F3. Alternatively, you can press Ctrl+Shift+T. This shows a dialog in which you can enter the class name to open it.