@Nonnull Path directory) {
        MavenProject prj = getMavenProject(requireNonNull(project, "project" + " cannot be null"));
        prj.addSourceRoot(
                requireNonNull(scope, "scope" + " cannot be null"),
                requireNonNull(language, "language" + " cannot be null"),
                requireNonNull(directory, "directory" + " cannot be null"));
    }

    @Override
    @Nonnull

### Best Practices

**Null Safety:**
```java
public Suggester(final Client client, final SuggestSettings settings) {
    this.client = Objects.requireNonNull(client, "client must not be null");
    this.settings = Objects.requireNonNull(settings, "settings must not be null");
}
```

**Logging with Context:**
```java
if (logger.isInfoEnabled()) {

      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    Builder<E> combine(Builder<E> other) {
      requireNonNull(impl);
      requireNonNull(other.impl);
      /*
       * For discussion of requireNonNull, see the comment on the field.
       *
       * (And I don't believe there's any situation in which we call x.combine(y) when x is a plain

            @Nullable List<RemoteRepository> repositories,
            @Nullable Nature nature) {
        return builder()
                .session(requireNonNull(session, "session cannot be null"))
                .artifactCoordinates(requireNonNull(artifactCoordinates, "artifactCoordinates cannot be null"))
                .repositories(repositories)
                .nature(nature)
                .build();
    }

      switch (balanceFactor()) {
        case -2:
          // requireNonNull is safe because right must exist in order to get a negative factor.
          requireNonNull(right);
          if (right.balanceFactor() > 0) {
            right = right.rotateRight();
          }
          return rotateLeft();
        case 2:
          // requireNonNull is safe because left must exist in order to get a positive factor.

        out.append(format.normalizeFirstWord(s.substring(i, j)));
      } else {
        requireNonNull(out).append(format.normalizeWord(s.substring(i, j)));
      }
      out.append(format.wordSeparator);
      i = j + wordSeparator.length();
    }
    return (i == 0)
        ? format.normalizeFirstWord(s)
        : requireNonNull(out).append(format.normalizeWord(s.substring(i))).toString();
  }

  /**

            VersionScheme versionScheme) {
        this.metadataResolver = Objects.requireNonNull(metadataResolver, "metadataResolver cannot be null");
        this.syncContextFactory = Objects.requireNonNull(syncContextFactory, "syncContextFactory cannot be null");
        this.repositoryEventDispatcher =
                Objects.requireNonNull(repositoryEventDispatcher, "repositoryEventDispatcher cannot be null");

      switch (balanceFactor()) {
        case -2:
          // requireNonNull is safe because right must exist in order to get a negative factor.
          requireNonNull(right);
          if (right.balanceFactor() > 0) {
            right = right.rotateRight();
          }
          return rotateLeft();
        case 2:
          // requireNonNull is safe because left must exist in order to get a positive factor.

        out.append(format.normalizeFirstWord(s.substring(i, j)));
      } else {
        requireNonNull(out).append(format.normalizeWord(s.substring(i, j)));
      }
      out.append(format.wordSeparator);
      i = j + wordSeparator.length();
    }
    return (i == 0)
        ? format.normalizeFirstWord(s)
        : requireNonNull(out).append(format.normalizeWord(s.substring(i))).toString();
  }

  /**

            final ExecutorService threadPool) {
        this.client = Objects.requireNonNull(client, "client must not be null");
        suggestSettings = Objects.requireNonNull(settings, "settings must not be null");
        this.readingConverter = Objects.requireNonNull(readingConverter, "readingConverter must not be null");
        this.contentsReadingConverter = Objects.requireNonNull(contentsReadingConverter, "contentsReadingConverter must not be null");