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Oracle Java SE 21 Developer Professional Sample Questions:

1. Given:
java
List<String> frenchAuthors = new ArrayList<>();
frenchAuthors.add("Victor Hugo");
frenchAuthors.add("Gustave Flaubert");
Which compiles?

A) Map<String, ArrayList<String>> authorsMap1 = new HashMap<>();
java
authorsMap1.put("FR", frenchAuthors);
B) Map<String, ? extends List<String>> authorsMap2 = new HashMap<String, ArrayList<String>> (); java authorsMap2.put("FR", frenchAuthors);
C) Map<String, List<String>> authorsMap5 = new HashMap<String, List<String>>(); java authorsMap5.put("FR", frenchAuthors);
D) Map<String, List<String>> authorsMap4 = new HashMap<String, ArrayList<String>>(); java authorsMap4.put("FR", frenchAuthors);
E) var authorsMap3 = new HashMap<>();
java
authorsMap3.put("FR", frenchAuthors);

2. Which three of the following are correct about the Java module system?

A) If a package is defined in both a named module and the unnamed module, then the package in the unnamed module is ignored.
B) The unnamed module exports all of its packages.
C) The unnamed module can only access packages defined in the unnamed module.
D) We must add a module descriptor to make an application developed using a Java version prior to SE9 run on Java 11.
E) Code in an explicitly named module can access types in the unnamed module.
F) If a request is made to load a type whose package is not defined in any known module, then the module system will attempt to load it from the classpath.

3. Given:
java
record WithInstanceField(String foo, int bar) {
double fuz;
}
record WithStaticField(String foo, int bar) {
static double wiz;
}
record ExtendingClass(String foo) extends Exception {}
record ImplementingInterface(String foo) implements Cloneable {}
Which records compile? (Select 2)

A) ImplementingInterface
B) WithInstanceField
C) WithStaticField
D) ExtendingClass

4. Consider the following methods to load an implementation of MyService using ServiceLoader. Which of the methods are correct? (Choose all that apply)

A) MyService service = ServiceLoader.getService(MyService.class);
B) MyService service = ServiceLoader.load(MyService.class).findFirst().get();
C) MyService service = ServiceLoader.services(MyService.class).getFirstInstance();
D) MyService service = ServiceLoader.load(MyService.class).iterator().next();

5. Given:
java
public class ExceptionPropagation {
public static void main(String[] args) {
try {
thrower();
System.out.print("Dom Perignon, ");
} catch (Exception e) {
System.out.print("Chablis, ");
} finally {
System.out.print("Saint-Emilion");
}
}
static int thrower() {
try {
int i = 0;
return i / i;
} catch (NumberFormatException e) {
System.out.print("Rose");
return -1;
} finally {
System.out.print("Beaujolais Nouveau, ");
}
}
}
What is printed?

A) Rose
B) Beaujolais Nouveau, Chablis, Dom Perignon, Saint-Emilion
C) Saint-Emilion
D) Beaujolais Nouveau, Chablis, Saint-Emilion

Solutions: