src/java.base/share/classes/java/util/LeapableRng.java
branchJDK-8193209-branch
changeset 57436 b0c958c0e6c6
parent 57435 9a4184201823
child 57437 f02ffcb61dce
--- a/src/java.base/share/classes/java/util/LeapableRng.java	Thu Jun 27 16:46:44 2019 -0300
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,151 +0,0 @@
-/*
- * Copyright (c) 2013, 2019, 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.  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).
- *
- * 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;
-
-import java.math.BigInteger;
-import java.util.stream.Stream;
-
-/**
- * This interface is designed to provide a common protocol for objects
- * that generate sequences of pseudorandom numbers (or Boolean values)
- * and furthermore can easily not only jump but also <i>leap</i> to
- * a very distant point in the state cycle.
- *
- * Typically one will construct a series of {@code LeapableRng} objects
- * by iterative leaping from a single original {@code LeapableRng}
- * object, and then for each such object produce a subseries of objects
- * by iterative jumping.  There is little conceptual difference between
- * leaping and jumping, but typically a leap will be a very long jump
- * in the state cycle (perhaps distance 2<sup>128</sup> or so).
- *
- * <p>Ideally, all {@code LeapableRng} objects produced by iterative
- * leaping and jumping from a single original {@code LeapableRng} object
- * are statistically independent of one another and individually uniform.
- * In practice, one must settle for some approximation to independence
- * and uniformity.  In particular, a specific implementation may
- * assume that each generator in a stream produced by the {@code leaps}
- * method is used to produce (by jumping) a number of objects no larger
- * than 2<sup>64</sup>.  Implementors are advised to use algorithms
- * whose period is at least 2<sup>191</sup>.
- *
- * <p>Methods are provided to perform a single leap operation and also
- * to produce a stream of generators produced from the original by
- * iterative copying and leaping of internal state.  The generators
- * produced must implement the {@code JumpableRng} interface but need
- * not also implement the {@code LeapableRng} interface.  A typical
- * strategy for a multithreaded application is to create a single
- * {@code LeapableRng} object, calls its {@code leaps} method exactly
- * once, and then parcel out generators from the resulting stream, one
- * to each thread.  Then the {@code jumps} method of each such generator
- * be called to produce a substream of generator objects.
- *
- * <p>An implementation of the {@code LeapableRng} interface must provide
- * concrete definitions for the methods {@code nextInt()}, {@code nextLong},
- * {@code period()}, {@code copy()}, {@code jump()}, {@code defaultJumpDistance()},
- * {@code leap()}, and {@code defaultLeapDistance()}.
- * Default implementations are provided for all other methods.
- *
- * <p>Objects that implement {@code java.util.LeapableRng} are
- * typically not cryptographically secure.  Consider instead using
- * {@link java.security.SecureRandom} to get a cryptographically
- * secure pseudo-random number generator for use by
- * security-sensitive applications.
- *
- * @author  Guy Steele
- * @since   1.9
- */
-public interface LeapableRng extends JumpableRng {
-    /**
-     * Returns a new generator whose internal state is an exact copy
-     * of this generator (therefore their future behavior should be
-     * identical if subjected to the same series of operations).
-     *
-     * @return a new object that is a copy of this generator
-     */
-    LeapableRng copy();
-
-    /**
-     * Alter the state of this pseudorandom number generator so as to
-     * leap forward a large, fixed distance (typically 2<sup>96</sup>
-     * or more) within its state cycle.
-     */
-    void leap();
-    
-    /**
-     * Returns the distance by which the {@code leap()} method will leap
-     * forward within the state cycle of this generator object.
-     *
-     * @return the default leap distance (as a {@code double} value)
-     */
-    double defaultLeapDistance();
-
-    /**
-     * Returns an effectively unlimited stream of new pseudorandom
-     * number generators, each of which implements the {@code JumpableRng}
-     * interface.
-     *
-     * @implNote It is permitted to implement this method in a manner
-     * equivalent to {@code leaps(Long.MAX_VALUE)}.
-     *
-     * @implNote The default implementation produces a sequential stream
-     * that  repeatedly calls {@code copy()} and {@code leap()} on this generator,
-     * and the copies become the generators produced by the stream.
-     *
-     * @return a stream of objects that implement the {@code JumpableRng} interface
-     */
-    default Stream<JumpableRng> leaps() {
-	return Stream.generate(this::copyAndLeap).sequential();
-    }
-
-    /**
-     * Returns a stream producing the given {@code streamSize} number of
-     * new pseudorandom number generators, each of which implements the
-     * {@code JumpableRng} interface.
-     *
-     * @implNote The default implementation produces a sequential stream
-     * that  repeatedly calls {@code copy()} and {@code leap()} on this generator,
-     * and the copies become the generators produced by the stream.
-     *
-     * @param streamSize the number of generators to generate
-     * @return a stream of objects that implement the {@code JumpableRng} interface
-     * @throws IllegalArgumentException if {@code streamSize} is
-     *         less than zero
-     */
-    default Stream<JumpableRng> leaps(long streamSize) {
-        return leaps().limit(streamSize);
-    }
-        
-    /**
-     * Copy this generator, leap this generator forward, then return the copy.
-     *
-     * @return a copy of this generator object before the leap occurred
-     */
-    default JumpableRng copyAndLeap() {
-	JumpableRng result = copy();
-	leap();
-	return result;
-    }
-
-}