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 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

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 * accompanied this code).

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package java.security.spec;

import java.math.BigInteger;

/**

 * This immutable class specifies the set of domain parameters

 * used with elliptic curve cryptography (ECC).

 *

 * @see AlgorithmParameterSpec

 *

 * @author Valerie Peng

 *

 * @since 1.5

 */

public class ECParameterSpec implements AlgorithmParameterSpec {

    private final EllipticCurve curve;

    private final ECPoint g;

    private final BigInteger n;

    private final int h;

    /**

     * Creates elliptic curve domain parameters based on the

     * specified values.

     * @param curve the elliptic curve which this parameter

     * defines.

     * @param g the generator which is also known as the base point.

     * @param n the order of the generator {@code g}.

     * @param h the cofactor.

     * @throws    NullPointerException if {@code curve},

     * {@code g}, or {@code n} is null.

     * @throws    IllegalArgumentException if {@code n}

     * or {@code h} is not positive.

     */

    public ECParameterSpec(EllipticCurve curve, ECPoint g,

                           BigInteger n, int h) {

        if (curve == null) {

            throw new NullPointerException("curve is null");

        }

        if (g == null) {

            throw new NullPointerException("g is null");

        }

        if (n == null) {

            throw new NullPointerException("n is null");

        }

        if (n.signum() != 1) {

            throw new IllegalArgumentException("n is not positive");

        }

        if (h <= 0) {

            throw new IllegalArgumentException("h is not positive");

        }

        this.curve = curve;

        this.g = g;

        this.n = n;

        this.h = h;

    }

    /**

     * Returns the elliptic curve that this parameter defines.

     * @return the elliptic curve that this parameter defines.

     */

    public EllipticCurve getCurve() {

        return curve;

    }

    /**

     * Returns the generator which is also known as the base point.

     * @return the generator which is also known as the base point.

     */

    public ECPoint getGenerator() {

        return g;

    }

    /**

     * Returns the order of the generator.

     * @return the order of the generator.

     */

    public BigInteger getOrder() {

        return n;

    }

    /**

     * Returns the cofactor.

     * @return the cofactor.

     */

    public int getCofactor() {

        return h;

    }

}