1z1-830問題集、Oracle実際の試験問題

質問 1

Given:
java
import java.io.*;
class A implements Serializable {
int number = 1;
}
class B implements Serializable {
int number = 2;
}
public class Test {
public static void main(String[] args) throws Exception {
File file = new File("o.ser");
A a = new A();
var oos = new ObjectOutputStream(new FileOutputStream(file));
oos.writeObject(a);
oos.close();
var ois = new ObjectInputStream(new FileInputStream(file));
B b = (B) ois.readObject();
ois.close();
System.out.println(b.number);
}
}
What is the given program's output?

A. NotSerializableException

B. ClassCastException

C. 1

D. Compilation fails

E. 2

正解: B

解説: (PassTest メンバーにのみ表示されます)

質問 2

Which of the following methods of java.util.function.Predicate aredefault methods?

A. isEqual(Object targetRef)

B. test(T t)

C. not(Predicate<? super T> target)

D. and(Predicate<? super T> other)

E. or(Predicate<? super T> other)

F. negate()

正解: D,E,F

解説: (PassTest メンバーにのみ表示されます)

質問 3

Given a properties file on the classpath named Person.properties with the content:
ini
name=James
And:
java
public class Person extends ListResourceBundle {
protected Object[][] getContents() {
return new Object[][]{
{"name", "Jeanne"}
};
}
}
And:
java
public class Test {
public static void main(String[] args) {
ResourceBundle bundle = ResourceBundle.getBundle("Person");
String name = bundle.getString("name");
System.out.println(name);
}
}
What is the given program's output?

A. JamesJeanne

B. Jeanne

C. JeanneJames

D. James

E. MissingResourceException

F. Compilation fails

正解: B

解説: (PassTest メンバーにのみ表示されます)

質問 4

Given:
java
package vehicule.parent;
public class Car {
protected String brand = "Peugeot";
}
and
java
package vehicule.child;
import vehicule.parent.Car;
public class MiniVan extends Car {
public static void main(String[] args) {
Car car = new Car();
car.brand = "Peugeot 807";
System.out.println(car.brand);
}
}
What is printed?

A. Compilation fails.

B. Peugeot 807

C. Peugeot

D. An exception is thrown at runtime.

正解: A

解説: (PassTest メンバーにのみ表示されます)

質問 5

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. [d, b]

B. [a, b]

C. [d]

D. An UnsupportedOperationException is thrown

E. An IndexOutOfBoundsException is thrown

F. [c, b]

正解: F

解説: (PassTest メンバーにのみ表示されます)

質問 6

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. The CopyOnWriteArrayList class does not allow null elements.

D. Element-changing operations on iterators of CopyOnWriteArrayList, such as remove, set, and add, are supported and do not throw UnsupportedOperationException.

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.

正解: E

解説: (PassTest メンバーにのみ表示されます)

質問 7

Given:
java
String s = " ";
System.out.print("[" + s.strip());
s = " hello ";
System.out.print("," + s.strip());
s = "h i ";
System.out.print("," + s.strip() + "]");
What is printed?

A. [,hello,hi]

B. [ , hello ,hi ]

C. [,hello,h i]

D. [ ,hello,h i]

正解: C

解説: (PassTest メンバーにのみ表示されます)

質問 8

What does the following code print?
java
import java.util.stream.Stream;
public class StreamReduce {
public static void main(String[] args) {
Stream<String> stream = Stream.of("J", "a", "v", "a");
System.out.print(stream.reduce(String::concat));
}
}

A. Java

B. null

C. Compilation fails

D. Optional[Java]

正解: D

解説: (PassTest メンバーにのみ表示されます)

質問 9

Given:
java
Integer frenchRevolution = 1789;
Object o1 = new String("1789");
Object o2 = frenchRevolution;
frenchRevolution = null;
Object o3 = o2.toString();
System.out.println(o1.equals(o3));
What is printed?

A. Compilation fails.

B. false

C. A NullPointerException is thrown.

D. true

E. A ClassCastException is thrown.

正解: D

解説: (PassTest メンバーにのみ表示されます)

Oracle Java SE 21 Developer Professional - 1z1-830 模擬練習