Java Development and Deployment Flashcards

Which `jar` command option lists the contents of an existing JAR file?

Answer: jar --list --file app.jar

`jar --list` (or `jar -tf`) lists all entries in the specified JAR archive.

When module-info.java contains `uses com.example.Printer;`, what does this indicate?

Answer: The module is a consumer of the Printer service via ServiceLoader

The `uses` directive registers the module as a consumer of a service type, allowing `ServiceLoader` to discover implementations at runtime.

Which Java 11 feature allows running a single-file source program without explicitly compiling it first?

Answer: java Hello.java

Java 11 added the ability to launch single-file source-code programs directly with `java SourceFile.java`, which compiles in memory.

What does the `--show-module-resolution` JVM flag output during startup?

Answer: A trace of which modules are being resolved and in what order

`--show-module-resolution` prints resolution steps at startup, useful for diagnosing module graph problems.

Which directory inside a module source tree conventionally holds the `module-info.java` file?

Answer: The root of the module's source directory

`module-info.java` is placed at the root of the module's source tree, at the same level as the top-level package directories.

What is the role of the `java.base` module in the Java module system?

Answer: It is the foundational module that every other module implicitly requires

`java.base` defines the core JDK APIs and is implicitly required by all modules; you never need to declare `requires java.base`.

Which option passed to `javac` enables preview features in Java 11?

Answer: --enable-preview combined with --release 11

Preview features require both `--enable-preview` and `--release ` (or `-source` / `-target`) so the compiler knows the exact release context.