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package java.util; |
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import java.security.SecureRandom; |
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import java.net.InetAddress; |
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import java.util.concurrent.atomic.AtomicLong; |
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import java.util.Spliterator; |
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import java.util.function.IntConsumer; |
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import java.util.function.LongConsumer; |
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import java.util.function.DoubleConsumer; |
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/** |
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* A generator of uniform pseudorandom values applicable for use in |
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* (among other contexts) isolated parallel computations that may |
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* generate subtasks. Class SplittableRandom supports methods for |
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* generate subtasks. Class {@code SplittableRandom} supports methods for |
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* producing pseudorandom numbers of type {@code int}, {@code long}, |
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* and {@code double} with similar usages as for class |
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* {@link java.util.Random} but differs in the following ways: |
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* |
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* </ul> |
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* |
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* <p>Instances of {@code SplittableRandom} are not cryptographically |
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* secure. Consider instead using {@link java.security.SecureRandom} |
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* in security-sensitive applications. Additionally, |
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* default-constructed instances do not use a cryptographically random |
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* seed unless the {@linkplain System#getProperty system property} |
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* {@code java.util.secureRandomSeed} is set to {@code true}. |
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* |
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* @author Guy Steele |
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* @author Doug Lea |
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* @since 1.8 |
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* cases, this split must be performed in a thread-safe manner, so |
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* we use an AtomicLong to represent the seed rather than use an |
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* explicit SplittableRandom. To bootstrap the seeder, we start |
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* off using a seed based on current time and host. This serves as |
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* a slimmed-down (and insecure) variant of SecureRandom that also |
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* off using a seed based on current time and host unless the |
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* java.util.secureRandomSeed property is set. This serves as a |
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* slimmed-down (and insecure) variant of SecureRandom that also |
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* avoids stalls that may occur when using /dev/random. |
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* |
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* It is a relatively simple matter to apply the basic design here |
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/** |
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* The seed generator for default constructors. |
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*/ |
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private static final AtomicLong seeder = |
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new AtomicLong(mix64((((long)hashedHostAddress()) << 32) ^ |
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System.currentTimeMillis()) ^ |
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mix64(System.nanoTime())); |
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> |
private static final AtomicLong seeder = new AtomicLong(initialSeed()); |
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|
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/** |
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* Returns hash of local host IP address, if available; else 0. |
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*/ |
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private static int hashedHostAddress() { |
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try { |
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return InetAddress.getLocalHost().hashCode(); |
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} catch (Exception ex) { |
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return 0; |
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} |
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> |
private static long initialSeed() { |
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> |
try { // ignore exceptions in accessing/parsing properties |
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> |
String pp = System.getProperty |
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("java.util.secureRandomSeed"); |
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> |
if (pp != null && pp.equalsIgnoreCase("true")) { |
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> |
byte[] seedBytes = java.security.SecureRandom.getSeed(8); |
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> |
long s = (long)(seedBytes[0]) & 0xffL; |
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for (int i = 1; i < 8; ++i) |
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> |
s = (s << 8) | ((long)(seedBytes[i]) & 0xffL); |
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return s; |
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> |
} |
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} catch (Exception ignore) { |
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} |
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> |
int hh = 0; // hashed host address |
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try { |
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> |
hh = InetAddress.getLocalHost().hashCode(); |
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> |
} catch (Exception ignore) { |
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> |
} |
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> |
return (mix64((((long)hh) << 32) ^ System.currentTimeMillis()) ^ |
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> |
mix64(System.nanoTime())); |
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} |
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// IllegalArgumentException messages |
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* Returns a pseudorandom {@code int} value between zero (inclusive) |
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* and the specified bound (exclusive). |
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* |
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* @param bound the bound on the random number to be returned. Must be |
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* positive. |
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> |
* @param bound the upper bound (exclusive). Must be positive. |
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* @return a pseudorandom {@code int} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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* Returns a pseudorandom {@code long} value between zero (inclusive) |
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* and the specified bound (exclusive). |
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* |
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* @param bound the bound on the random number to be returned. Must be |
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* positive. |
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* @param bound the upper bound (exclusive). Must be positive. |
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* @return a pseudorandom {@code long} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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* (inclusive) and one (exclusive). |
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* |
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* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive) |
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* (inclusive) and one (exclusive) |
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*/ |
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public double nextDouble() { |
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return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
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* Returns a pseudorandom {@code double} value between 0.0 |
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* (inclusive) and the specified bound (exclusive). |
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* |
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< |
* @param bound the bound on the random number to be returned. Must be |
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* positive. |
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> |
* @param bound the upper bound (exclusive). Must be positive. |
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* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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* origin (inclusive) and bound (exclusive). |
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* |
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* @param origin the least value returned |
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* @param bound the upper bound |
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> |
* @param bound the upper bound (exclusive) |
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* @return a pseudorandom {@code double} value between the origin |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code origin} is greater than |
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|
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/** |
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* Returns a stream producing the given {@code streamSize} number |
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< |
* of pseudorandom {@code int} values, each conforming to the |
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< |
* given origin and bound. |
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> |
* of pseudorandom {@code int} values from this generator and/or one split |
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> |
* from it; each value conforms to the given origin (inclusive) and bound |
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> |
* (exclusive). |
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* |
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* @param streamSize the number of values to generate |
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* @param randomNumberOrigin the origin of each random value |
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* @param randomNumberBound the bound of each random value |
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> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
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> |
* @param randomNumberBound the bound (exclusive) of each random value |
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* @return a stream of pseudorandom {@code int} values, |
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< |
* each with the given origin and bound |
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> |
* each with the given origin (inclusive) and bound (exclusive) |
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* @throws IllegalArgumentException if {@code streamSize} is |
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* less than zero, or {@code randomNumberOrigin} |
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* is greater than or equal to {@code randomNumberBound} |
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|
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/** |
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* Returns an effectively unlimited stream of pseudorandom {@code |
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< |
* int} values, each conforming to the given origin and bound. |
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> |
* int} values from this generator and/or one split from it; each value |
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> |
* conforms to the given origin (inclusive) and bound (exclusive). |
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* |
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* @implNote This method is implemented to be equivalent to {@code |
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* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
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* |
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< |
* @param randomNumberOrigin the origin of each random value |
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< |
* @param randomNumberBound the bound of each random value |
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> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
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> |
* @param randomNumberBound the bound (exclusive) of each random value |
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* @return a stream of pseudorandom {@code int} values, |
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< |
* each with the given origin and bound |
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> |
* each with the given origin (inclusive) and bound (exclusive) |
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* @throws IllegalArgumentException if {@code randomNumberOrigin} |
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* is greater than or equal to {@code randomNumberBound} |
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*/ |
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|
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/** |
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* Returns a stream producing the given {@code streamSize} number of |
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< |
* pseudorandom {@code long} values, each conforming to the |
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< |
* given origin and bound. |
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> |
* pseudorandom {@code long} values from this generator and/or one split |
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> |
* from it; each value conforms to the given origin (inclusive) and bound |
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> |
* (exclusive). |
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* |
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* @param streamSize the number of values to generate |
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< |
* @param randomNumberOrigin the origin of each random value |
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< |
* @param randomNumberBound the bound of each random value |
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> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
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> |
* @param randomNumberBound the bound (exclusive) of each random value |
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* @return a stream of pseudorandom {@code long} values, |
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< |
* each with the given origin and bound |
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> |
* each with the given origin (inclusive) and bound (exclusive) |
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* @throws IllegalArgumentException if {@code streamSize} is |
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* less than zero, or {@code randomNumberOrigin} |
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* is greater than or equal to {@code randomNumberBound} |
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|
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/** |
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* Returns an effectively unlimited stream of pseudorandom {@code |
| 723 |
< |
* long} values, each conforming to the given origin and bound. |
| 723 |
> |
* long} values from this generator and/or one split from it; each value |
| 724 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
| 725 |
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* |
| 726 |
|
* @implNote This method is implemented to be equivalent to {@code |
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* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
| 728 |
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* |
| 729 |
< |
* @param randomNumberOrigin the origin of each random value |
| 730 |
< |
* @param randomNumberBound the bound of each random value |
| 729 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
| 730 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
| 731 |
|
* @return a stream of pseudorandom {@code long} values, |
| 732 |
< |
* each with the given origin and bound |
| 732 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
| 733 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
| 734 |
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* is greater than or equal to {@code randomNumberBound} |
| 735 |
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*/ |
| 744 |
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|
| 745 |
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/** |
| 746 |
|
* Returns a stream producing the given {@code streamSize} number of |
| 747 |
< |
* pseudorandom {@code double} values, each between zero |
| 748 |
< |
* (inclusive) and one (exclusive). |
| 747 |
> |
* pseudorandom {@code double} values from this generator and/or one split |
| 748 |
> |
* from it; each value is between zero (inclusive) and one (exclusive). |
| 749 |
|
* |
| 750 |
|
* @param streamSize the number of values to generate |
| 751 |
|
* @return a stream of {@code double} values |
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|
| 764 |
|
/** |
| 765 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
| 766 |
< |
* double} values, each between zero (inclusive) and one |
| 767 |
< |
* (exclusive). |
| 766 |
> |
* double} values from this generator and/or one split from it; each value |
| 767 |
> |
* is between zero (inclusive) and one (exclusive). |
| 768 |
|
* |
| 769 |
|
* @implNote This method is implemented to be equivalent to {@code |
| 770 |
|
* doubles(Long.MAX_VALUE)}. |
| 780 |
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|
| 781 |
|
/** |
| 782 |
|
* Returns a stream producing the given {@code streamSize} number of |
| 783 |
< |
* pseudorandom {@code double} values, each conforming to the |
| 784 |
< |
* given origin and bound. |
| 783 |
> |
* pseudorandom {@code double} values from this generator and/or one split |
| 784 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
| 785 |
> |
* (exclusive). |
| 786 |
|
* |
| 787 |
|
* @param streamSize the number of values to generate |
| 788 |
< |
* @param randomNumberOrigin the origin of each random value |
| 789 |
< |
* @param randomNumberBound the bound of each random value |
| 788 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
| 789 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
| 790 |
|
* @return a stream of pseudorandom {@code double} values, |
| 791 |
< |
* each with the given origin and bound |
| 791 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
| 792 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
| 793 |
< |
* less than zero |
| 793 |
> |
* less than zero |
| 794 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
| 795 |
|
* is greater than or equal to {@code randomNumberBound} |
| 796 |
|
*/ |
| 808 |
|
|
| 809 |
|
/** |
| 810 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
| 811 |
< |
* double} values, each conforming to the given origin and bound. |
| 811 |
> |
* double} values from this generator and/or one split from it; each value |
| 812 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
| 813 |
|
* |
| 814 |
|
* @implNote This method is implemented to be equivalent to {@code |
| 815 |
|
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
| 816 |
|
* |
| 817 |
< |
* @param randomNumberOrigin the origin of each random value |
| 818 |
< |
* @param randomNumberBound the bound of each random value |
| 817 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
| 818 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
| 819 |
|
* @return a stream of pseudorandom {@code double} values, |
| 820 |
< |
* each with the given origin and bound |
| 820 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
| 821 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
| 822 |
|
* is greater than or equal to {@code randomNumberBound} |
| 823 |
|
*/ |
