Oracle Java SE 21 Developer Professional 認定 1z1-830 試験問題:

1. Given:
java
Object input = 42;
String result = switch (input) {
case String s -> "It's a string with value: " + s;
case Double d -> "It's a double with value: " + d;
case Integer i -> "It's an integer with value: " + i;
};
System.out.println(result);
What is printed?

A) Compilation fails.
B) It throws an exception at runtime.
C) null
D) It's a string with value: 42
E) It's an integer with value: 42
F) It's a double with value: 42

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

3. Which methods compile?

A) ```java public List<? super IOException> getListSuper() { return new ArrayList<Exception>(); } csharp
B) ```java
public List<? extends IOException> getListExtends() {
return new ArrayList<FileNotFoundException>();
}
C) ```java
public List<? super IOException> getListSuper() {
return new ArrayList<FileNotFoundException>();
}
D) ```java public List<? extends IOException> getListExtends() { return new ArrayList<Exception>(); } csharp

4. Given:
java
StringBuilder result = Stream.of("a", "b")
.collect(
() -> new StringBuilder("c"),
StringBuilder::append,
(a, b) -> b.append(a)
);
System.out.println(result);
What is the output of the given code fragment?

A) cacb
B) cbca
C) bac
D) abc
E) cba
F) bca
G) acb

5. Given:
java
List<String> frenchAuthors = new ArrayList<>();
frenchAuthors.add("Victor Hugo");
frenchAuthors.add("Gustave Flaubert");
Which compiles?

A) Map<String, List<String>> authorsMap4 = new HashMap<String, ArrayList<String>>(); java authorsMap4.put("FR", frenchAuthors);
B) Map<String, ArrayList<String>> authorsMap1 = new HashMap<>();
java
authorsMap1.put("FR", frenchAuthors);
C) var authorsMap3 = new HashMap<>();
java
authorsMap3.put("FR", frenchAuthors);
D) Map<String, ? extends List<String>> authorsMap2 = new HashMap<String, ArrayList<String>> (); java authorsMap2.put("FR", frenchAuthors);
E) Map<String, List<String>> authorsMap5 = new HashMap<String, List<String>>(); java authorsMap5.put("FR", frenchAuthors);

質問と回答：