About Oracle 1z0-830 Exam Guide

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Oracle Java SE 21 Developer Professional Sample Questions:

1. Given:
var cabarets = new TreeMap<>();
cabarets.put(1, "Moulin Rouge");
cabarets.put(2, "Crazy Horse");
cabarets.put(3, "Paradis Latin");
cabarets.put(4, "Le Lido");
cabarets.put(5, "Folies Bergere");
System.out.println(cabarets.subMap(2, true, 5, false));
What is printed?

A) An exception is thrown at runtime.
B) {2=Crazy Horse, 3=Paradis Latin, 4=Le Lido}
C) Compilation fails.
D) CopyEdit{2=Crazy Horse, 3=Paradis Latin, 4=Le Lido, 5=Folies Bergere}
E) {}

2. Which methods compile?

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

3. Given:
java
Stream<String> strings = Stream.of("United", "States");
BinaryOperator<String> operator = (s1, s2) -> s1.concat(s2.toUpperCase()); String result = strings.reduce("-", operator); System.out.println(result); What is the output of this code fragment?

A) -UnitedSTATES
B) United-STATES
C) United-States
D) UnitedStates
E) -UNITEDSTATES
F) UNITED-STATES
G) -UnitedStates

4. How would you create a ConcurrentHashMap configured to allow a maximum of 10 concurrent writer threads and an initial capacity of 42?
Which of the following options meets this requirement?

A) var concurrentHashMap = new ConcurrentHashMap(42, 0.88f, 10);
B) var concurrentHashMap = new ConcurrentHashMap(42);
C) var concurrentHashMap = new ConcurrentHashMap();
D) None of the suggestions.
E) var concurrentHashMap = new ConcurrentHashMap(42, 10);

5. What do the following print?
java
public class DefaultAndStaticMethods {
public static void main(String[] args) {
WithStaticMethod.print();
}
}
interface WithDefaultMethod {
default void print() {
System.out.print("default");
}
}
interface WithStaticMethod extends WithDefaultMethod {
static void print() {
System.out.print("static");
}
}