Java Platform Module System Flashcards

Which of the following is NOT a valid module directive in module-info.java?

Answer: exports transitive

`exports transitive` is not valid syntax; `transitive` is a modifier for `requires`, not `exports`.

What does `requires static com.annotation;` mean in a module declaration?

Answer: The module requires com.annotation at compile time but it is optional at runtime

`requires static` is a compile-time-only dependency; the module can still run if com.annotation is absent from the module path at runtime.

When running `java --list-modules`, what does the output show?

Answer: All observable modules in the current JDK/JRE installation

`--list-modules` prints all observable platform and installed modules available in the current Java runtime.

Which of the following best describes an 'open module' declared as `open module com.app { }`?

Answer: All packages are open for deep reflection at runtime by any module

An `open module` implicitly opens all its packages for deep reflection at runtime, equivalent to adding `opens` for every package.

Which `javac` option is used to compile a module-info.java file along with other source files in the correct module source path layout?

Answer: --module-source-path

`--module-source-path` tells javac where to find source files for multiple modules in a modular project layout.

What is the effect of placing a JAR on the classpath (not module path) in a modular application?

Answer: It becomes part of the unnamed module

All JARs on the classpath are consolidated into a single unnamed module, which has no module-info and can access all exported packages.

Which `java` command-line option forces an additional module to be resolved even if it is not required by the root module?

Answer: --add-modules

`--add-modules` adds the specified modules to the default set of root modules during module resolution.