Refactor multiple If' statements in Java-8

Question

I need to validate mandatory fields in my class

For example, 9 fields must not be null.

I need to check if they are all null but I

Answer 1

All the Object.isNull might be replaced with Optional object and its methods. Let's take example the line:

if (!Objects.isNull(excess.getLimit()) && Objects.isNull(excess.getLimit().getId())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[3]);
}

Would be simplified to (and squeezed on 1 line remains readable):

Optional.ofNullable(excess.getLimit())                                // check the Limit
        .map(limit -> limit.getId())                                  // if not null, getId
        .ifPresent(i -> builder.append(MANDATORY_EXCESS_FIELDS[3]));  // Append if present

And for the String.isEmpty(s) check, you have to create Optional in this way:

Optional.ofNullable(excess.getStatus()).filter(s -> !StringUtils.isEmpty(s))

---

A short way would be to pass those Optional object into the map and use the index to iterate through them and perform an action. int count is a number of checkings:

Map> map = new HashMap<>();
map.put(...);
map.put(1, Optional.ofNullable(excess.getStatus()).filter(s -> !StringUtils.isEmpty(s)));
map.put(...);
map.put(3, Optional.ofNullable(excess.getLimit()).map(limit -> limit.getId()));
map.put(...);

for (int index=0; index mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[index]));
}

And the for-cycle might be simplified as well:

IntStream.range(0, count).forEach(index -> 
    map.get(index)
       .ifPresent(any -> mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[index])));