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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

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

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

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

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package java.security.spec;

import java.math.BigInteger;

import java.util.Arrays;

/**

 * This immutable class defines an elliptic curve (EC) prime

 * finite field.

 *

 * @see ECField

 *

 * @author Valerie Peng

 *

 * @since 1.5

 */

public class ECFieldFp implements ECField {

    private BigInteger p;

    /**

     * Creates an elliptic curve prime finite field

     * with the specified prime {@code p}.

     * @param p the prime.

     * @throws    NullPointerException if {@code p} is null.

     * @throws    IllegalArgumentException if {@code p}

     * is not positive.

     */

    public ECFieldFp(BigInteger p) {

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

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

        }

        this.p = p;

    }

    /**

     * Returns the field size in bits which is size of prime p

     * for this prime finite field.

     * @return the field size in bits.

     */

    public int getFieldSize() {

        return p.bitLength();

    };

    /**

     * Returns the prime {@code p} of this prime finite field.

     * @return the prime.

     */

    public BigInteger getP() {

        return p;

    }

    /**

     * Compares this prime finite field for equality with the

     * specified object.

     * @param obj the object to be compared.

     * @return true if {@code obj} is an instance

     * of ECFieldFp and the prime value match, false otherwise.

     */

    public boolean equals(Object obj) {

        if (this == obj)  return true;

        return obj instanceof ECFieldFp other

                && p.equals(other.p);

    }

    /**

     * Returns a hash code value for this prime finite field.

     * @return a hash code value.

     */

    public int hashCode() {

        return p.hashCode();

    }

}