Computer scienceProgramming languagesJavaCode organizationFunctional programmingFunctions

Optional

Theory

Sum up optional values

Report a typo

The method getValues of the ValueProvider class returns a List<Optional<Integer>> result.

class ValueProvider {
    public List<Optional<Integer>> getValues() {
        // hidden code
    }
}

Write a code in the Main class that sums up all values and prints the result. If Optional object is empty, just skip it.

Sample Input 1: 

3
1
2
3

Sample Output 1: 

6

Sample Input 2: 

5
1
2
null
4
5

Sample Output 2: 

12
Write a program in Java 17
import java.util.List;
import java.util.Optional;

class Main {
public static void main(String[] args) {
ValueProvider provider = new ValueProvider();
// use provider.getValues() to get List<Optional<Integer>>
}
}

class ValueProvider {
private List<Optional<Integer>> opts; // cache to provide reproducing method invocation

public List<Optional<Integer>> getValues() {
if (opts != null) {
return opts;
}

java.util.Scanner scanner = new java.util.Scanner(System.in);
int number = scanner.nextInt();
opts = java.util.stream.IntStream
.rangeClosed(1, number)
.mapToObj(n -> {
String val = scanner.next();
return "null".equals(val) ?
Optional.<Integer>empty() :
Optional.of(Integer.valueOf(val));
})
.collect(java.util.stream.Collectors.toList());

return opts;
}
}
___

Create a free account to access the full topic