@CheckReturnValue
  public static boolean equal(@Nullable Object a, @Nullable Object b) {
    return a == b || (a != null && a.equals(b));
  }
Determines whether two possibly-null objects are equal. Returns:

<ul>
  <li>{@code true} if {@code a} and {@code b} are both null.
  <li>{@code true} if {@code a} and {@code b} are both non-null and they are equal according to
      {@link Object#equals(Object)}.
  <li>{@code false} in all other situations.
</ul>

<p>This assumes that any non-null objects passed to this function conform to the {@code
equals()} contract.
fbcore/src/main/java/com/facebook/common/internal/Objects.java