FAQ Why doesn't my program start when I click the Run button?
Eclipse is not only a Java development environment. To deal with everything that can be launched with it—Java programs, JUnit tests, Enterprise JavaBeans™ (EJBs), even Eclipse itself—Eclipse defines the concept of launch configurations. When you click the Run button, click on Java Application, fill out the details, and click Run. The next time, your program will be launched automatically when you click the Run button (or press Ctrl+F11). To alter your launch configuration or to create a new one, select the Run... menu option, in the Run button drop-down menu. Alternatively, you can edit a launch configuration by holding down Ctrl and clicking on the launch you want to edit in the Run or Debug button drop-down list.
The other Run button—the one with the toolbox—is for launching external development tools and scripts, such as Ant, from within Eclipse. Generally, this
icon is for launching tools that operate on the resources in your workspace rather than for launching programs you are building in your workspace.