Oracle 1z0-830

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Oracle Java SE 21 Developer Professional Sample Questions:

1. Given:
java
void verifyNotNull(Object input) {
boolean enabled = false;
assert enabled = true;
assert enabled;
System.out.println(input.toString());
assert input != null;
}
When does the given method throw a NullPointerException?

A) Only if assertions are disabled and the input argument isn't null
B) Only if assertions are disabled and the input argument is null
C) A NullPointerException is never thrown
D) Only if assertions are enabled and the input argument isn't null
E) Only if assertions are enabled and the input argument is null

2. Given:
java
var ceo = new HashMap<>();
ceo.put("Sundar Pichai", "Google");
ceo.put("Tim Cook", "Apple");
ceo.put("Mark Zuckerberg", "Meta");
ceo.put("Andy Jassy", "Amazon");
Does the code compile?

A) False
B) True

3. 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) 1
B) ClassCastException
C) 2
D) Compilation fails
E) NotSerializableException

4. Given:
java
Period p = Period.between(
LocalDate.of(2023, Month.MAY, 4),
LocalDate.of(2024, Month.MAY, 4));
System.out.println(p);
Duration d = Duration.between(
LocalDate.of(2023, Month.MAY, 4),
LocalDate.of(2024, Month.MAY, 4));
System.out.println(d);
What is the output?

A) P1Y
UnsupportedTemporalTypeException
B) P1Y
PT8784H
C) UnsupportedTemporalTypeException
D) PT8784H
P1Y

5. Given:
java
public class Test {
class A {
}
static class B {
}
public static void main(String[] args) {
// Insert here
}
}
Which three of the following are valid statements when inserted into the given program?

A) B b = new B();
B) A a = new Test.A();
C) A a = new Test().new A();
D) B b = new Test.B();
E) B b = new Test().new B();
F) A a = new A();

Solutions: