Free 1z0-830: Java SE 21 Developer Professional Exam Questions and Answers

Last updated: September 19, 2026

Provider

Oracle

Questions in our bank

1000+

Free to read

First 10, with answers

Our test mode duration & pass mark

130 mins · 70%

Verified answers

Reviewed weekly

Practice format

Multiple choice

Recommended: Switch to Test Mode to start a practice test that simulates the real exam experience.

1. Question #1

   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. MissingResourceException
   • B. Compilation fails
   • C. James
   • D. JeanneJames
   • E. JamesJeanne
   • F. Jeanne
   Reveal Answer

2. Question #2

   Given: java public class Versailles { int mirrorsCount; int gardensHectares; void Versailles() { // n1 this.mirrorsCount = 17; this.gardensHectares = 800; System.out.println("Hall of Mirrors has " + mirrorsCount + " mirrors."); System.out.println("The gardens cover " + gardensHectares + " hectares."); } public static void main(String[] args) { var castle = new Versailles(); // n2 } } What is printed?

   • A. nginxHall of Mirrors has 17 mirror
   • B. The gardens cover 800 hectares.
   • C. Nothing
   • D. An exception is thrown at runtime.
   • E. Compilation fails at line n1.
   • F. Compilation fails at line n2.
   Reveal Answer

3. Question #3

   Given: java String s = " "; System.out.print("[" + s.strip()); s = " hello "; System.out.print("," + s.strip()); s = "h i "; System.out.print("," + s.strip() + "]"); What is printed?

   • A. [ ,hello,h i]
   • B. [,hello,h i]
   • C. [,hello,hi]
   • D. [ , hello ,hi ]
   Reveal Answer

4. Question #4

   Given: java StringBuffer us = new StringBuffer("US"); StringBuffer uk = new StringBuffer("UK"); Stream<StringBuffer> stream = Stream.of(us, uk); String output = stream.collect(Collectors.joining("-", "=", "")); System.out.println(output); What is the given code fragment's output?

   • A. US-UK
   • B. An exception is thrown.
   • C. -US=UK
   • D. =US-UK
   • E. Compilation fails.
   • F. US=UK
   Reveal Answer

5. Question #5

   Given: java Runnable task1 = () -> System.out.println("Executing Task-1"); Callable<String> task2 = () -> { System.out.println("Executing Task-2"); return "Task-2 Finish."; }; ExecutorService execService = Executors.newCachedThreadPool(); // INSERT CODE HERE execService.awaitTermination(3, TimeUnit.SECONDS); execService.shutdownNow(); Which of the following statements, inserted in the code above, printsboth: "Executing Task-2" and "Executing Task-1"?

   Select 2 answers.

   • A. execService.call(task1);
   • B. execService.call(task2);
   • C. execService.execute(task1);
   • D. execService.execute(task2);
   • E. execService.run(task1);
   • F. execService.run(task2);
   • G. execService.submit(task1);
   • H. execService.submit(task2);
   Reveal Answer

6. Question #6

   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? true; Is Car sealed? true; Is Bike sealed? true
   • B. Is Vehicle sealed? false; Is Car sealed? false; Is Bike sealed? false
   • C. Is Vehicle sealed? true; Is Car sealed? false; Is Bike sealed? false
   • D. Is Vehicle sealed? false; Is Car sealed? true; Is Bike sealed? true
   Reveal Answer

7. Question #7

   Which of the following statements are correct?

   • A. You can use 'private' access modifier with all kinds of classes
   • B. You can use 'protected' access modifier with all kinds of classes
   • C. You can use 'public' access modifier with all kinds of classes
   • D. You can use 'final' modifier with all kinds of classes
   • E. None
   Reveal Answer

8. Question #8

   Given: java Period p = Period.between( LocalDate.of(2023, Month.MAY, 4), LocalDate.of(2024, Month.MAY, 4)); System.out.println(p); Duration d = Duration.between( LocalDate.of(2023, Month.MAY, 4), LocalDate.of(2024, Month.MAY, 4)); System.out.println(d); What is the output?

   • A. P1Y PT8784H
   • B. PT8784H P1Y
   • C. UnsupportedTemporalTypeException
   • D. P1YUnsupportedTemporalTypeException
   Reveal Answer

9. Question #9

   A module com.eiffeltower.shop with the related sources in the src directory. That module requires com.eiffeltower.membership, available in a JAR located in the lib directory. What is the command to compile the module com.eiffeltower.shop?

   • A. bashCopyEditjavac -source src -p lib/com.eiffel.membership.jar -d out -m com.eiffeltower.shop
   • B. css CopyEditjavac --module-source-path src -p lib/com.eiffel.membership.jar -d out -m com.eiffeltower.shop
   • C. css CopyEditjavac --module-source-path src -p lib/com.eiffel.membership.jar -s out -m com.eiffeltower.shop
   • D. css CopyEditjavac -path src -p lib/com.eiffel.membership.jar -d out -m com.eiffeltower.shop
   Reveal Answer

10. Question #10

    Given: java var hauteCouture = new String[]{ "Chanel", "Dior", "Louis Vuitton" }; var i = 0; do { System.out.print(hauteCouture[i] + " "); } while (i++ > 0); What is printed?

    • A. Chanel
    • B. Chanel Dior Louis Vuitton
    • C. An ArrayIndexOutOfBoundsException is thrown at runtime.
    • D. Compilation fails.
    Reveal Answer