Eclipse includes a wide assortment of configuration options that control project compilation or enhance productivity. Don't get overwhelmed by the number of choices, but get started and gradually expand the customizations to suit your personal style and team development standards.
Each Java project includes a builder that compiles its resources from source into output folders. A simple project has no builders, and other project types can add relevant builders that apply appropriate compilers or transformation utilities to the files.
A project is built automatically; that is, the builder is applied automatically whenever a file is saved. For Java projects, the builder uses the Java compiler settings configured in the workspace preferences or overridden in a project.
A Java project's Java build path defines which projects from the workspace and which JAR archive files are included in the class path when building or running the project.
User libraries provide a convenient mechanism to define named collections of related JAR files that are used in combination. For example, J2EE standard APIs or the Apache Axis Web Services toolkit are good candidates for user libraries.
A hybrid configuration is possible where third-party JAR files are collected in an external directory. Some of these archives are packaged in one or more named user libraries, and all are easily accessible from within Eclipse using a simple project and linked file location.