private static EllipticCurve getParameterSpecNistCurve(EciesParameters.CurveType curveType) {
    if (curveType == EciesParameters.CurveType.NIST_P256) {
      return EllipticCurves.getNistP256Params().getCurve();
    }
    if (curveType == EciesParameters.CurveType.NIST_P384) {
      return EllipticCurves.getNistP384Params().getCurve();
    }
    if (curveType == EciesParameters.CurveType.NIST_P521) {
      return EllipticCurves.getNistP521Params().getCurve();
    }
    throw new IllegalArgumentException("Unable to determine NIST curve type for " + curveType);
  }
Exactly one of nistPublicPoint and x25519PublicPointBytes is non-null.
java_src/src/main/java/com/google/crypto/tink/hybrid/EciesPublicKey.java