Given the code fragments:
class Employee {
Optional<Address> address;
Employee (Optional<Address> address) {
this.address = address;
}
public Optional<Address> getAddress() { return address; }
}
class Address {
String city = "New York";
public String getCity { return city: }
public String toString() {
return city;
}
}
and
Address address = null;
Optional<Address> addrs1 = Optional.ofNullable (address);
Employee e1 = new Employee (addrs1);
String eAddress = (addrs1.isPresent()) ? addrs1.get().getCity() : "City Not available";
What is the result?

Given:

Your design requires that:
fuelLevel of Engine must be greater than zero when the start()method is invoked.

The code must terminate if fuelLevelof Engineis less than or equal to zero.

Which code fragment should be added at line n1to express this invariant condition?

Given:
class Student {
String course, name, city;
public Student (String name, String course, String city) {
this.course = course; this.name = name; this.city = city;
}
public String toString() {
return course + ":" + name + ":" + city;
}
public String getCourse() {return course;}
public String getName() {return name;}
public String getCity() {return city;}
and the code fragment:
List<Student> stds = Arrays.asList(
new Student ("Jessy", "Java ME", "Chicago"),
new Student ("Helen", "Java EE", "Houston"),
new Student ("Mark", "Java ME", "Chicago"));
stds.stream()
. collect(Collectors.groupingBy(Student::getCourse))
. forEach(src, res) -> System.out.println(scr));
What is the result?

Given the code fragment:
public class FileThread implements Runnable {
String fName;
public FileThread(String fName) { this.fName = fName; }
public void run () System.out.println(fName);}
public static void main (String[] args) throws IOException, InterruptedException {
ExecutorService executor = Executors.newCachedThreadPool();
Stream<Path> listOfFiles = Files.walk(Paths.get("Java Projects"));
listOfFiles.forEach(line -> {
executor.execute(new FileThread(line.getFileName().toString())); //
line n1
});
executor.shutdown();
executor.awaitTermination(5, TimeUnit.DAYS);//
line n2
}
}
The Java Projects directory exists and contains a list of files.
What is the result?

Which two reasons should you use interfaces instead of abstract classes? (Choose two.)