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Oracle 1z1-830 Exam Syllabus Topics:

Oracle Java SE 21 Developer Professional Sample Questions:

1. Given:
java
List<String> l1 = new ArrayList<>(List.of("a", "b"));
List<String> l2 = new ArrayList<>(Collections.singletonList("c"));
Collections.copy(l1, l2);
l2.set(0, "d");
System.out.println(l1);
What is the output of the given code fragment?

A) [c, b]
B) An IndexOutOfBoundsException is thrown
C) An UnsupportedOperationException is thrown
D) [a, b]
E) [d, b]
F) [d]

2. Given:
java
List<String> abc = List.of("a", "b", "c");
abc.stream()
.forEach(x -> {
x = x.toUpperCase();
});
abc.stream()
.forEach(System.out::print);
What is the output?

A) An exception is thrown.
B) ABC
C) abc
D) Compilation fails.

3. Given:
java
var sList = new CopyOnWriteArrayList<Customer>();
Which of the following statements is correct?

A) The CopyOnWriteArrayList class's iterator reflects all additions, removals, or changes to the list since the iterator was created.
B) The CopyOnWriteArrayList class is not thread-safe and does not prevent interference amongconcurrent threads.
C) Element-changing operations on iterators of CopyOnWriteArrayList, such as remove, set, and add, are supported and do not throw UnsupportedOperationException.
D) The CopyOnWriteArrayList class does not allow null elements.
E) The CopyOnWriteArrayList class is a thread-safe variant of ArrayList where all mutative operations are implemented by making a fresh copy of the underlying array.

4. 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"?

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

5. 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) [Lyon, Lille, Toulouse]
D) [Lille, Lyon]
E) [Paris]

Solutions: