public static int fieldSizeInBits(EllipticCurve curve) throws GeneralSecurityException {
    return getModulus(curve).subtract(BigInteger.ONE).bitLength();
  }
Returns the size of an element of the field over which the curve is defined.

@param curve must be a prime order elliptic curve
@return the size of an element in bits
java_src/src/main/java/com/google/crypto/tink/subtle/EllipticCurves.java