guava/src/com/google/common/collect/StandardTable.java
@Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    return rowKey != null && columnKey != null && super.contains(rowKey, columnKey);
  }
@Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    return rowKey != null && columnKey != null && super.contains(rowKey, columnKey);
  }
Accessors