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Oracle 1z0-830 Exam Syllabus Topics:

Oracle Java SE 21 Developer Professional Sample Questions:

Question 1

Given:
java
sealed class Vehicle permits Car, Bike {
}
non-sealed class Car extends Vehicle {
}
final class Bike extends Vehicle {
}
public class SealedClassTest {
public static void main(String[] args) {
Class<?> vehicleClass = Vehicle.class;
Class<?> carClass = Car.class;
Class<?> bikeClass = Bike.class;
System.out.print("Is Vehicle sealed? " + vehicleClass.isSealed() +
"; Is Car sealed? " + carClass.isSealed() +
"; Is Bike sealed? " + bikeClass.isSealed());
}
}
What is printed?

A. Is Vehicle sealed? false; Is Car sealed? false; Is Bike sealed? false
B. Is Vehicle sealed? true; Is Car sealed? true; Is Bike sealed? true
C. Is Vehicle sealed? false; Is Car sealed? true; Is Bike sealed? true
D. Is Vehicle sealed? true; Is Car sealed? false; Is Bike sealed? false

Question 2

Given:
java
var frenchCities = new TreeSet<String>();
frenchCities.add("Paris");
frenchCities.add("Marseille");
frenchCities.add("Lyon");
frenchCities.add("Lille");
frenchCities.add("Toulouse");
System.out.println(frenchCities.headSet("Marseille"));
What will be printed?

A. Compilation fails
B. [Paris, Toulouse]
C. [Paris]
D. [Lille, Lyon]
E. [Lyon, Lille, Toulouse]

Question 3

Given:
java
public class Test {
public static void main(String[] args) throws IOException {
Path p1 = Path.of("f1.txt");
Path p2 = Path.of("f2.txt");
Files.move(p1, p2);
Files.delete(p1);
}
}
In which case does the given program throw an exception?

A. File f2.txt exists while file f1.txt doesn't
B. An exception is always thrown
C. File f1.txt exists while file f2.txt doesn't
D. Neither files f1.txt nor f2.txt exist
E. Both files f1.txt and f2.txt exist

Question 4

Given:
java
Optional<String> optionalName = Optional.ofNullable(null);
String bread = optionalName.orElse("Baguette");
System.out.print("bread:" + bread);
String dish = optionalName.orElseGet(() -> "Frog legs");
System.out.print(", dish:" + dish);
try {
String cheese = optionalName.orElseThrow(() -> new Exception());
System.out.println(", cheese:" + cheese);
} catch (Exception exc) {
System.out.println(", no cheese.");
}
What is printed?

A. bread:bread, dish:dish, cheese.
B. Compilation fails.
C. bread:Baguette, dish:Frog legs, no cheese.
D. bread:Baguette, dish:Frog legs, cheese.

Question 5

Given a properties file on the classpath named Person.properties with the content:
ini
name=James
And:
java
public class Person extends ListResourceBundle {
protected Object[][] getContents() {
return new Object[][]{
{"name", "Jeanne"}
};
}
}
And:
java
public class Test {
public static void main(String[] args) {
ResourceBundle bundle = ResourceBundle.getBundle("Person");
String name = bundle.getString("name");
System.out.println(name);
}
}
What is the given program's output?

A. Compilation fails
B. JeanneJames
C. JamesJeanne
D. Jeanne
E. MissingResourceException
F. James

Solutions: