@Override
    public int hashCode() {
        // see Map.Entry API specification
        return (getKey() == null ? 0 : getKey().hashCode()) ^
                (getValue() == null ? 0 : getValue().hashCode());
    }
<p>Returns a suitable hash code.
The hash code follows the definition in {@code Map.Entry}.</p>

@return the hash code
android/android_framework/base/src/main/java/lang3/tuple/Pair.java