Compilation types
IntelliJ IDEA suggests several ways of compiling and building applications. The corresponding commands are available in the menu.
Compile <compilation_scope>. All the source files in the specified scope are compiled. The scope in this case may be a file, a package, and so on. Refer to the section Compile and build for details.
Build Project. All the source files in the entire project modified since the last compilation, are compiled. Dependent source files, if appropriate, are also compiled. Additionally, the tasks tied to the compilation or build process on the modified sources are performed. For example, EJB validation is performed, if the corresponding option is enabled on the Validation page.
Build Module. Compiles recursively are all the source files which have been modified since the last compilation in the selected module, as well as in all the modules it depends on.
Rebuild Project. All the source files in the project are recompiled. This may be necessary when the classpath entries have changed, for example, SDKs or libraries being used added, removed or altered.