Optional usage in java to save chain-invocation

Code optimization: chain-invokation saver - Optional

Chain-invokation presents normally in our code, which looks like

company.getLeaderDepartment().getLeader().getName() // unsafe

codes like above may easy to cause NPE (Null Pointer Exception)

To solve this problem:

if (company != null) {
	if (compnay.getLeaderDepartment() != null) {
		if (company.getLeaderDepartment().getLeader() != null) {
			String name = company.getLeaderDepartment().getLeader().getName(); // safe now
		}
	}
}

But how to make the code more elegant?

Use Library Optional

Source Code:

Optional has an empty object:

private static final Optional<?> EMPTY = new Optional<>();

Optional has two methods:

of: // must not be null, or throws exception
public static <T> Optional<T> of(T value) {
	return new Optional<>(value);
}
ofNullable: // can be null
public static <T> Optional<T> ofNullable(T value) {
	return value == null ? empty() : of(value);
}

using provided map api, we can try to convert one type to another type

public<U> Optional<U> map(Function<? super T, ? extends U> mapper) {
  Objects.requireNonNull(mapper);
  if (!isPresent())
    return empty();
  else {
    return Optional.ofNullable(mapper.apply(value));
  }
}

we also have two methods to get value

public T orElse(T other) {
  return value != null ? value : other; // get a default value
}
public T orElseGet(Supplier<? extends T> other) {
  return value != null ? value : other.get(); // invoke a passing functional supplier interface[1]
}

finally, our code should look like

Optional.ofNullable(company)
  .map(Company::getLeaderDepartment)
  .map(Department::getLeader)
  .map(People::getName)
  .orElse(StringUtils.EMPTY);

[1].

functional supplier interface:

() -> return T;

functional consumer interface:

(T t) -> void();