1Z0-819 Modules System 5

Question 1

What is the module name for the foundational Java SE module that all other modules implicitly depend on?

Accepted Answer

java.base

Answer

java.base is the foundational platform module containing java.lang, java.util, java.io, etc., and every module implicitly requires it.

Question 2

What command lists all observable modules in the current JDK installation?

Accepted Answer

java --list-modules

Answer

'java --list-modules' outputs all platform and observable modules available to the current JDK.

Question 3

A module-info.java declares 'opens com.example.data to com.google.gson;'. What capability does this grant?

Accepted Answer

com.google.gson can reflectively access all members including private ones in com.example.data

Answer

A qualified 'opens' directive allows the target module to use reflection on all members, including private ones, in the opened package.

Question 4

What is the key difference between placing a JAR on --class-path versus --module-path?

Accepted Answer

On --class-path it joins the unnamed module; on --module-path it becomes an automatic or named module

Answer

Classpath JARs are aggregated into the unnamed module, while module-path JARs become named or automatic modules with encapsulation enforced.

Question 5

Which @Deprecated attribute, added in Java 9 alongside the module system, marks an API slated for removal?

Accepted Answer

forRemoval=true

Answer

The 'forRemoval=true' attribute on @Deprecated was added in Java 9 to signal that an API is scheduled for removal in a future release.

(1Z0-819) Oracle Java SE 11 Developer Practice Test