You could start with the almost-obligatory "HelloWorld.java" program that teaches basic program structure and the elements required. You can find a tutorial using an appropriate Google search that either shows how to create and run the program using a basic text editor at the command line (recommended) or using Eclipse. If you've decided on Eclipse as your IDE, construct and run the HelloWorld program using both the command line and IDE approaches so that you see what Eclipse does for you and have an idea what you'll have to do without Eclipse.
Learning Java using Eclipse on OpenSUSE 11.2
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