Oracle 1z0-830

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Oracle Java SE 21 Developer Professional Sample Questions:

1. Which three of the following are correct about the Java module system?

A) The unnamed module exports all of its packages.
B) We must add a module descriptor to make an application developed using a Java version prior to SE9 run on Java 11.
C) The unnamed module can only access packages defined in the unnamed module.
D) If a package is defined in both a named module and the unnamed module, then the package in the unnamed module is ignored.
E) If a request is made to load a type whose package is not defined in any known module, then the module system will attempt to load it from the classpath.
F) Code in an explicitly named module can access types in the unnamed module.

2. Given:
java
Object myVar = 0;
String print = switch (myVar) {
case int i -> "integer";
case long l -> "long";
case String s -> "string";
default -> "";
};
System.out.println(print);
What is printed?

A) Compilation fails.
B) string
C) integer
D) long
E) nothing
F) It throws an exception at runtime.

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

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

5. Given:
java
Deque<Integer> deque = new ArrayDeque<>();
deque.offer(1);
deque.offer(2);
var i1 = deque.peek();
var i2 = deque.poll();
var i3 = deque.peek();
System.out.println(i1 + " " + i2 + " " + i3);
What is the output of the given code fragment?

A) 1 1 1
B) 1 2 2
C) An exception is thrown.
D) 2 1 1
E) 1 2 1
F) 2 1 2
G) 2 2 1
H) 1 1 2
I) 2 2 2

Solutions: