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Monday, April 6, 2026

10 1Z0–830 Sample Questions for Java 21 Certification Exam Practice

Without any further ado, here are the 10 sample questions for Java 21 certification exam, also known 1Z0–830 exam. I will also share solution and explanation at the end of the article for you very soon but before that I would like you to solve this question and paste your answer in comments.

You are given the following code snippet:

String[] letters = {"x", "y", "z", "w", "v", "u"};
String output = "Sequence:";
for (String ch : letters) {
 output += "-" + ch;
}

Which of the following code fragments produces the same result as the above loop using Java Streams?

String output = Arrays.stream(letters)
 .reduce("Sequence:", (s1, s2) -> s1 + "-" + s2);

String output = "Sequence:";
output += Arrays.stream(letters).parallel()
 .reduce((s1, s2) -> s1 + "-" + s2).get();

String output = Arrays.stream(letters).parallel()
 .reduce("Sequence:", (s1, s2) -> s1 + "-" + s2);

String output = "Sequence:";
output += Arrays.stream(letters).parallel()
 .reduce("", (s1, s2) -> s1 + "-" + s2);

2. Given the code fragment:

String[] txt = {"AB", "CD"};
x:
for (String value : txt) {
 var values = value.toCharArray();
 for (int i = values.length - 1; i >= 0; i--) {
 if (i < 1) continue x;
 else if (values[i] == 'C') break;
 System.out.println(txt[i]);
 }
}

What is the result?

A) A
B) ABD
C) AD
D) AB
E) CDCD
F) ABAB
G) No output is produced.

3. Which local variable initialization statement is correct?

A) var 24H = Duration.ofHours(24);
B) var backslashChar = '\\';
C) var doubleSlash = "\\\\";
D) var underscoreIndex = "A_Z".indexOf("_"); E) None of the above

4. Given following code, what would be the result?

int[] values = {-1,-2,0,2,1};
Deque<Integer> numbers = new ArrayDeque<>();
for (int i = 0; i < values.length; i++) {
 if (i%2 == 0) {
 numbers.offerFirst(Integer.valueOf(values[i]));
 }else{
 numbers.offerLast(Integer.valueOf(values[i]));
 }
}
System.out.println(numbers);

Options are:

A. [1, 0, -1, -2, 2]

B. [-1, 0, -1, -2, 2]

C. [-1, 0, 1, -2, 2]

D. [-1, -2, -0, 1, 2]

E. None of the Above

5. What is the output of this program?

public class Test {
 public static String test(Number value) {
 return switch(value) {
 case Double num when num > 0 -> "Positive";
 case Double num when num < 0 -> "Negative";
 case Double num when num == 0 -> "Zero";
 default -> "Invalid";
 };
 }

 public static void main(String[] args) {
 try {
  Number num = Integer.valueOf(1);
 System.out.println(test(num));
 num = null;
 System.out.println(test(num));
 } catch(Exception e) {
 System.out.println("Error");
 }
 }
}

A.
Error
Error

B.
Invalid
Error

C.
Positive
Invalid

D.
Invalid
Invalid

E.
Positive
Error

F. None of the above

6. What is the output of this code?

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("CM");
var x = LocalDate.of(2001, 2, 5);
var y = Period.ofMonths(3).plusDays(1);
var z = x.plus(y);
System.out.println(fmt.format(z));

A. 56

B. 83

C. 38

D. 65

E. None of the above

7. Given:

IntStream.concat(IntStream.range(0,3), IntStream.range(3,7))
 .parallel()
 .sorted()
 .filter(i -> i < 5 && i > 1)
 .mapToObj(i -> String.valueOf(i))
 .forEach(s -> Logger.getLogger("test").log(Level.INFO, String.valueOf(s)));

What is the result?

Options:

A. Values of 2 3 4 are logged in unpredictable order

B. Values of 6 5 1 0 are logged in this order

C. Values of 0 1 5 6 are logged in unpredictable order

D. Values of 4 3 2 are logged in this order

E. Values of 2 3 4 are logged in this order

F. Values of 0 1 5 6 are logged in this order

G. None of the above

8. Given the code fragment:

List<Integer> nums = Collections.synchronizedList(new ArrayList<>());
Callable<String> c = () -> {
 for (int i = 0; i < 5; i++) {
 nums.add(i);
 }
 return null;
};
Collection<Callable<String>> tasks = List.of(c, c, c); // Three identical Callable instances
ExecutorService es = Executors.newFixedThreadPool(2);
try {
 List<Future<String>> results = es.invokeAll(tasks);
 es.shutdown();
 nums.stream().forEach(i -> System.out.print(i));
} catch (InterruptedException e) {
 System.out.println("error");
}

What is the result?

Options:

A. Some of the integers in the range 0 to 4 in the ascending order are printed.

B. Some of the integers in the range 0 to 4 in the descending order are printed.

C. All of the integers in the range 0 to 4 in the ascending order are printed. Each integer appears 3 times the result.

D. None of the above

9. Given

List<Integer> nums = Collections.synchronizedList(new ArrayList<>());

Callable<String> c = () -> {
 for (int i = 0; i < 5; i++) {
 nums.add(i);
 }
 return null;
};
Collection<Callable<String>> tasks = List.of(c, c, c);
ExecutorService es = Executors.newFixedThreadPool(2);
try {
 List<Future<String>> results = es.invokeAll(tasks);
 es.shutdown();
 nums.stream().forEach(i -> System.out.print(i));
} catch (InterruptedException e) {
 System.out.println("error");
}

What is the result?

Options:

A. Some of the integers in the range 0 to 4 in ascending order are printed.

B. Some of the integers in the range 0 to 4 in descending order are printed.

C. All of the integers in the range 0 to 4 in ascending order are printed. Each integer appears 3 times in the result.

D. All of the integers in the range 0 to 4 in stochastic (random) order are printed. Each integer appears 3 times in the result.

E. Some of the integers in the range 0 to 4 in stochastic (random) order are printed.

F. All of the integers in the range 0 to 4 in descending order are printed. Each integer appears 3 times in the result.

G. The word “error” is printed.

H. None of the above

10. Given

public record Food(String name, int calories) {}

public class Test {
 public static void main(String[] args) {
 Food[] foods = {new Food("Apple", 200),
 new Food("Banana", 400),
 new Food("Cake", 800),
 new Food("Donut", 700)};
 // Line n1
 }
}

Which code fragment, when inserted at Line n1, finds a Food object with the lowest number of calories from a stream of randomly selected Food objects?

Options:

Food food = IntStream.generate(() -> ThreadLocalRandom.current().nextInt(foods.length-1))
 .limit(10)
 .mapToObj(i -> foods[i])
 .max((f1, f2) -> f1.calories() - f2.calories())
 .get();

Food food = IntStream.generate(() -> ThreadLocalRandom.current().nextInt(foods.length-1))
 .mapToObj(i -> foods[i])
 .sorted((f1, f2) -> f1.calories() - f2.calories())
 .findFirst()
 .get();

Food food = IntStream.generate(() -> ThreadLocalRandom.current().nextInt(foods.length))
 .mapToObj(i -> foods[i])
 .sorted((f1, f2) -> f1.calories() - f2.calories())
 .findFirst()
 .get();

D. Both of them

E. None of the above

Top Java 21 Certification 1Z0–830 Resources (Books, Courses, and Practice Tests)

As many of you also asked for Java 21 certification resources to crack the 1Z0–830 exam like books, online courses, and practice tests so here they are

Books

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2. Courses

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3. Practice Tests

Here are the practice tests courses you can take on Udemy. These contains multiple choice and multi-selection questions for you to practice in exam like environment.

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That’s all on these Java 21 Certification Sample question post guys. I hope you like these questions. Try to solve them today and I will update the post with answers tomorrow or day after tomorrow.

And, in case you need. have also shared more than 266+ questions on my Udemy course“1Z0–830 Java SE 21 Developer Professional Exam Practice Test” and you can use coupon code JAVA21FANS to get it for just $9.9.

Other Java 21 Exam related articles which I have shared earlier

Thank for reading this article, if you like this article then please share with you friends and colleagues, if you got any questions then feel free to ask.

P.S. — If you are looking for a course to prepare for Java SE 17 certification then Oracle Java Certification — Java 17 Practice Testfrom Udemy is the right place to start it. It explains about new features of Java17 required for OCAJP 17 exam.