/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.util;

/**
 * An interface to operating system provided cryptographically secure
 * pseudo random number generator.
 */
public abstract class SystemRandom implements AutoCloseable {

    /**
     * Only internal implementations are allowed.
     */
    SystemRandom() {
    }

    /**
     * Constructs and returns new instance of cryptographically secure
     * pseudo random number generator. The instance should be {@link #close closed}
     * when not needed any more, since it may hold a system resource.
     *
     * @return new instance of SystemRandom
     * @throws java.lang.UnsupportedOperationException if system does not
     *                                                 provide cryptographically
     *                                                 secure pseudo random
     *                                                 number generator
     */
    public static SystemRandom newInstance() {
        return new SystemRandomImpl();
    }

    /**
     * Fills the provided array with random bytes.
     *
     * @param bytes the array of bytes to be filled with random values.
     * @throws java.lang.IllegalStateException if this SystemRandom
     *                                         instance is already closed.
     * @throws java.lang.NullPointerException  if provided bytes array is null
     */
    public abstract void getBytes(byte[] bytes);

    /**
     * Closes this SystemRandom instance, releasing any system resource
     * it may hold.
     */
    @Override
    public abstract void close();
}