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

Given: Deque<Integer> dq = new ArrayDeque<>(); dq.offerFirst(1); dq.offerLast(2); dq.push(3); dq.addLast(4); dq.pollLast(); dq.removeFirst(); System.out.println(dq); What is the result?

• AA. [1, 2]
• BB. [1, 2, 4]
• CC. [3, 1, 2]
• DD. [3, 1]

Given: int total = 0; outer: for (int i = 1; i <= 4; i++) { for (int j = 1; j <= 4; j++) { if (j == 3) continue outer; if (i == 3) break outer; total += i * j; } } System.out.println(total); Which two statements are true? (Choose two.)

Select 2 answers.

• AA. The inner loop completes all four iterations when i is 1.
• BB. The continue outer statement ends the outer loop immediately.
• CC. The variable i is never 4 when the body of the inner loop runs.
• DD. The program prints 9.

Given: List<String> words = List.of("kiwi", "fig", "plum", "apple", "pear"); String result = words.stream() .filter(w -> w.length() > 3) .sorted(Comparator.comparing(String::length) .thenComparing(Comparator.reverseOrder())) .collect(Collectors.joining("|")); System.out.println(result); What is the result?

• AA. fig|plum|pear|kiwi|apple
• BB. apple|plum|pear|kiwi
• CC. kiwi|pear|plum|apple
• DD. plum|pear|kiwi|apple

Given: String a = "java"; String b = a.concat(""); String c = new StringBuilder("ja").append("va").toString(); String x = "ja"; String d = x + "va"; System.out.println(a == b); // line 1 System.out.println(a == c); // line 2 System.out.println(a == d); // line 3 System.out.println(a == c.intern()); // line 4 Which two lines print true? (Choose two.)

Select 2 answers.

• AA. Line 1
• BB. Line 2
• CC. Line 3
• DD. Line 4

Given: class DataException extends Exception { } static void load() throws IOException, DataException { } Which two code fragments compile when placed in a main method that has no throws clause? (Choose two.)

Select 2 answers.

• AA. try { load(); } catch (IOException | DataException e) { System.out.println(e.getMessage()); }
• BB. try { load(); } catch (IOException | DataException e) { e = null; }
• CC. try { load(); } catch (IOException e) { } catch (Exception e) { }
• DD. try { load(); } catch (DataException | Exception e) { System.out.println(e); }

Given: NumberFormat pf = NumberFormat.getPercentInstance(Locale.US); pf.setMinimumFractionDigits(1); System.out.println(pf.format(0.0724) + " " + pf.format(1.5)); What is the output?

• AA. 7% 150%
• BB. 7.2% 150%
• CC. 7.2% 150.0%
• DD. 7.24% 150.0%

Given the following module declarations: module com.app.util { exports com.app.util.text; } module com.app.core { requires transitive com.app.util; exports com.app.core.api; opens com.app.core.model to com.app.json; } module com.app.web { requires com.app.core; } Which statement is true about code in module com.app.web?

• AA. It can use public types from com.app.util.text without declaring a requires directive for com.app.util.
• BB. It can compile against public types in com.app.core.model because that package is opened.
• CC. It must declare requires com.app.util before it can use public types from com.app.util.text.
• DD. It can use reflection to read private fields of classes in com.app.core.api.

Which two statements are true? (Choose two.)

Select 2 answers.

• AA. A pool created by Executors.newFixedThreadPool(2) stops its worker threads once all submitted tasks have finished.
• BB. A thread created with Thread.ofVirtual().unstarted(task) remains in the NEW state until start() is called.
• CC. The JVM waits for all running virtual threads to finish before it exits when the main thread ends.
• DD. An exception thrown by a Callable submitted to an ExecutorService is rethrown from Future.get() wrapped in an ExecutionException.

Which statement about a record class declared in Java 21 is true?

• AA. A record can declare additional instance fields in its body if they are private and final.
• BB. A record can declare an instance initializer block that runs before the canonical constructor.
• CC. A record can declare static fields and static initializer blocks in its body.
• DD. A record can extend an abstract class that declares a no-argument constructor.

Given: var parts = Stream.of("kiwi", "fig", "plum", "pear", "apple") .collect(Collectors.partitioningBy( s -> s.length() > 3, Collectors.mapping(s -> s.substring(0, 1), Collectors.joining()))); System.out.println(parts); What is the output?

• AA. {false=fig, true=kiwiplumpearapple}
• BB. {false=[f], true=[k, p, p, a]}
• CC. {false=f, true=kppa}
• DD. {true=kppa, false=f}