Java Development and Deployment Flashcards

Which command compiles a Java source file named `Hello.java` and places the output in a directory called `out`?

Answer: javac -d out Hello.java

The `javac -d ` option specifies the destination directory for compiled `.class` files.

What is the result of running `java -jar app.jar` when the manifest file has no `Main-Class` attribute?

Answer: An error is thrown indicating no main manifest attribute

Without a `Main-Class` attribute in MANIFEST.MF, the JVM cannot determine the entry point and reports an error.

Which module directive is used to allow reflective access to all packages in a module by a specific other module?

Answer: opens to

The `opens` directive grants reflective access (e.g., for frameworks) while `exports` only grants compile/run-time API access.

What does the `javap -c` command display for a `.class` file?

Answer: Disassembled JVM bytecode instructions

`javap -c` disassembles and prints the bytecode instructions for each method in the class file.

In a multi-release JAR, where should Java 11-specific class files be placed?

Answer: META-INF/versions/11/

Multi-release JARs place version-specific classes under `META-INF/versions//` where N is the Java version.

Which `java` command-line option sets the module path?

Answer: --module-path

`--module-path` (or `-p`) specifies where the JVM looks for named modules, analogous to `-classpath` for the legacy class path.

What happens when you use `requires transitive com.example.util;` in a module descriptor?

Answer: Modules that require your module automatically also read com.example.util

`requires transitive` implies that any module depending on your module implicitly also depends on `com.example.util`, enabling implied readability.