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package java.util; |
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import java.security.SecureRandom; |
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import java.net.NetworkInterface; |
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import java.util.Enumeration; |
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import java.util.concurrent.atomic.AtomicLong; |
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import java.util.function.DoubleConsumer; |
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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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import java.util.stream.StreamSupport; |
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import java.util.stream.DoubleStream; |
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import java.util.stream.IntStream; |
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import java.util.stream.LongStream; |
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import java.util.stream.DoubleStream; |
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import java.util.stream.StreamSupport; |
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/** |
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* A generator of uniform pseudorandom values applicable for use in |
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* types and ranges, but similar properties are expected to hold, at |
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* least approximately, for others as well. The <em>period</em> |
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* (length of any series of generated values before it repeats) is at |
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* least 2<sup>64</sup>. </li> |
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* least 2<sup>64</sup>. |
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* |
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* <li> Method {@link #split} constructs and returns a new |
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* <li>Method {@link #split} constructs and returns a new |
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* SplittableRandom instance that shares no mutable state with the |
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* current instance. However, with very high probability, the |
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* values collectively generated by the two objects have the same |
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* statistical properties as if the same quantity of values were |
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* generated by a single thread using a single {@code |
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* SplittableRandom} object. </li> |
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* SplittableRandom} object. |
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* |
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* <li>Instances of SplittableRandom are <em>not</em> thread-safe. |
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* They are designed to be split, not shared, across threads. For |
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* |
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* <li>This class provides additional methods for generating random |
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* streams, that employ the above techniques when used in {@code |
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* stream.parallel()} mode.</li> |
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* stream.parallel()} mode. |
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* |
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* </ul> |
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* |
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* @author Doug Lea |
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* @since 1.8 |
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*/ |
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public class SplittableRandom { |
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> |
public final class SplittableRandom { |
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|
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/* |
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* Implementation Overview. |
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* For nextLong, the mix64 function is based on David Stafford's |
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* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html) |
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* "Mix13" variant of the "64-bit finalizer" function in Austin |
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* Appleby's MurmurHash3 algorithm See |
113 |
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* http://code.google.com/p/smhasher/wiki/MurmurHash3 . The mix32 |
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* Appleby's MurmurHash3 algorithm (see |
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* http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32 |
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* function is based on Stafford's Mix04 mix function, but returns |
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* the upper 32 bits cast as int. |
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* |
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* other cases, this split must be performed in a thread-safe |
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* manner, so we use an AtomicLong to represent the seed rather |
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* than use an explicit SplittableRandom. To bootstrap the |
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* defaultGen, we start off using a seed based on current time and |
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* network interface address unless the java.util.secureRandomSeed |
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* property is set. This serves as a slimmed-down (and insecure) |
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* variant of SecureRandom that also avoids stalls that may occur |
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* when using /dev/random. |
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* defaultGen, we start off using a seed based on current time |
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* unless the java.util.secureRandomSeed property is set. This |
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* serves as a slimmed-down (and insecure) variant of SecureRandom |
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* that also 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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* to use 128 bit seeds. However, emulating 128bit arithmetic and |
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* The least non-zero value returned by nextDouble(). This value |
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* is scaled by a random value of 53 bits to produce a result. |
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*/ |
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private static final double DOUBLE_ULP = 1.0 / (1L << 53); |
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> |
private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53); |
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/** |
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* The seed. Updated only via method nextSeed. |
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* Computes Stafford variant 13 of 64bit mix function. |
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*/ |
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private static long mix64(long z) { |
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z *= 0xbf58476d1ce4e5b9L; |
196 |
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z = (z ^ (z >>> 32)) * 0x94d049bb133111ebL; |
197 |
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return z ^ (z >>> 32); |
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} |
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|
200 |
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private static long xmix64(long z) { |
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z *= 0xbf58476d1ce4e5b9L; |
191 |
> |
z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; |
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z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; |
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return z ^ (z >>> 31); |
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} |
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* Returns the 32 high bits of Stafford variant 4 mix64 function as int. |
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*/ |
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private static int mix32(long z) { |
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< |
z *= 0x62a9d9ed799705f5L; |
200 |
> |
z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L; |
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return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); |
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} |
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* Returns the gamma value to use for a new split instance. |
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*/ |
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private static long mixGamma(long z) { |
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z *= 0xff51afd7ed558ccdL; // MurmurHash3 mix constants |
208 |
> |
z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants |
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z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
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z = (z ^ (z >>> 33)) | 1L; // force to be odd |
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int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions |
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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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long h = 0L; |
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try { |
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Enumeration<NetworkInterface> ifcs = |
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NetworkInterface.getNetworkInterfaces(); |
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boolean retry = false; // retry once if getHardwareAddress is null |
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while (ifcs.hasMoreElements()) { |
254 |
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NetworkInterface ifc = ifcs.nextElement(); |
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if (!ifc.isVirtual()) { // skip fake addresses |
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byte[] bs = ifc.getHardwareAddress(); |
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if (bs != null) { |
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int n = bs.length; |
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int m = Math.min(n >>> 1, 4); |
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for (int i = 0; i < m; ++i) |
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h = (h << 16) ^ (bs[i] << 8) ^ bs[n-1-i]; |
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if (m < 4) |
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h = (h << 8) ^ bs[n-1-m]; |
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h = mix64(h); |
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break; |
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} |
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else if (!retry) |
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retry = true; |
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else |
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break; |
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} |
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} |
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} catch (Exception ignore) { |
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} |
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return (h ^ mix64(System.currentTimeMillis()) ^ |
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return (mix64(System.currentTimeMillis()) ^ |
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mix64(System.nanoTime())); |
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} |
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// IllegalArgumentException messages |
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< |
static final String BadBound = "bound must be positive"; |
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static final String BadRange = "bound must be greater than origin"; |
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static final String BadSize = "size must be non-negative"; |
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> |
static final String BAD_BOUND = "bound must be positive"; |
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> |
static final String BAD_RANGE = "bound must be greater than origin"; |
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> |
static final String BAD_SIZE = "size must be non-negative"; |
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|
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/* |
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* Internal versions of nextX methods used by streams, as well as |
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* @return a pseudorandom value |
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*/ |
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final double internalNextDouble(double origin, double bound) { |
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< |
double r = (nextLong() >>> 11) * DOUBLE_ULP; |
347 |
> |
double r = (nextLong() >>> 11) * DOUBLE_UNIT; |
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if (origin < bound) { |
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r = r * (bound - origin) + origin; |
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if (r >= bound) // correct for rounding |
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* may, and typically does, vary across program invocations. |
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*/ |
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public SplittableRandom() { // emulate defaultGen.split() |
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< |
long s = defaultGen.getAndAdd(2*GOLDEN_GAMMA); |
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> |
long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA); |
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this.seed = mix64(s); |
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this.gamma = mixGamma(s + GOLDEN_GAMMA); |
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} |
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*/ |
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public int nextInt(int bound) { |
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if (bound <= 0) |
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< |
throw new IllegalArgumentException(BadBound); |
419 |
> |
throw new IllegalArgumentException(BAD_BOUND); |
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// Specialize internalNextInt for origin 0 |
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int r = mix32(nextSeed()); |
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int m = bound - 1; |
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*/ |
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public int nextInt(int origin, int bound) { |
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if (origin >= bound) |
447 |
< |
throw new IllegalArgumentException(BadRange); |
447 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
448 |
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return internalNextInt(origin, bound); |
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} |
450 |
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|
468 |
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*/ |
469 |
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public long nextLong(long bound) { |
470 |
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if (bound <= 0) |
471 |
< |
throw new IllegalArgumentException(BadBound); |
471 |
> |
throw new IllegalArgumentException(BAD_BOUND); |
472 |
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// Specialize internalNextLong for origin 0 |
473 |
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long r = mix64(nextSeed()); |
474 |
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long m = bound - 1; |
496 |
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*/ |
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public long nextLong(long origin, long bound) { |
498 |
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if (origin >= bound) |
499 |
< |
throw new IllegalArgumentException(BadRange); |
499 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
500 |
|
return internalNextLong(origin, bound); |
501 |
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} |
502 |
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|
508 |
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* (inclusive) and one (exclusive) |
509 |
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*/ |
510 |
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public double nextDouble() { |
511 |
< |
return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP; |
511 |
> |
return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
512 |
|
} |
513 |
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|
514 |
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/** |
522 |
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*/ |
523 |
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public double nextDouble(double bound) { |
524 |
|
if (!(bound > 0.0)) |
525 |
< |
throw new IllegalArgumentException(BadBound); |
526 |
< |
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound; |
525 |
> |
throw new IllegalArgumentException(BAD_BOUND); |
526 |
> |
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; |
527 |
|
return (result < bound) ? result : // correct for rounding |
528 |
|
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
529 |
|
} |
541 |
|
*/ |
542 |
|
public double nextDouble(double origin, double bound) { |
543 |
|
if (!(origin < bound)) |
544 |
< |
throw new IllegalArgumentException(BadRange); |
544 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
545 |
|
return internalNextDouble(origin, bound); |
546 |
|
} |
547 |
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|
569 |
|
*/ |
570 |
|
public IntStream ints(long streamSize) { |
571 |
|
if (streamSize < 0L) |
572 |
< |
throw new IllegalArgumentException(BadSize); |
572 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
573 |
|
return StreamSupport.intStream |
574 |
|
(new RandomIntsSpliterator |
575 |
|
(this, 0L, streamSize, Integer.MAX_VALUE, 0), |
610 |
|
public IntStream ints(long streamSize, int randomNumberOrigin, |
611 |
|
int randomNumberBound) { |
612 |
|
if (streamSize < 0L) |
613 |
< |
throw new IllegalArgumentException(BadSize); |
613 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
614 |
|
if (randomNumberOrigin >= randomNumberBound) |
615 |
< |
throw new IllegalArgumentException(BadRange); |
615 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
616 |
|
return StreamSupport.intStream |
617 |
|
(new RandomIntsSpliterator |
618 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
636 |
|
*/ |
637 |
|
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
638 |
|
if (randomNumberOrigin >= randomNumberBound) |
639 |
< |
throw new IllegalArgumentException(BadRange); |
639 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
640 |
|
return StreamSupport.intStream |
641 |
|
(new RandomIntsSpliterator |
642 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
655 |
|
*/ |
656 |
|
public LongStream longs(long streamSize) { |
657 |
|
if (streamSize < 0L) |
658 |
< |
throw new IllegalArgumentException(BadSize); |
658 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
659 |
|
return StreamSupport.longStream |
660 |
|
(new RandomLongsSpliterator |
661 |
|
(this, 0L, streamSize, Long.MAX_VALUE, 0L), |
696 |
|
public LongStream longs(long streamSize, long randomNumberOrigin, |
697 |
|
long randomNumberBound) { |
698 |
|
if (streamSize < 0L) |
699 |
< |
throw new IllegalArgumentException(BadSize); |
699 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
700 |
|
if (randomNumberOrigin >= randomNumberBound) |
701 |
< |
throw new IllegalArgumentException(BadRange); |
701 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
702 |
|
return StreamSupport.longStream |
703 |
|
(new RandomLongsSpliterator |
704 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
722 |
|
*/ |
723 |
|
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
724 |
|
if (randomNumberOrigin >= randomNumberBound) |
725 |
< |
throw new IllegalArgumentException(BadRange); |
725 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
726 |
|
return StreamSupport.longStream |
727 |
|
(new RandomLongsSpliterator |
728 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
741 |
|
*/ |
742 |
|
public DoubleStream doubles(long streamSize) { |
743 |
|
if (streamSize < 0L) |
744 |
< |
throw new IllegalArgumentException(BadSize); |
744 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
745 |
|
return StreamSupport.doubleStream |
746 |
|
(new RandomDoublesSpliterator |
747 |
|
(this, 0L, streamSize, Double.MAX_VALUE, 0.0), |
784 |
|
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
785 |
|
double randomNumberBound) { |
786 |
|
if (streamSize < 0L) |
787 |
< |
throw new IllegalArgumentException(BadSize); |
787 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
788 |
|
if (!(randomNumberOrigin < randomNumberBound)) |
789 |
< |
throw new IllegalArgumentException(BadRange); |
789 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
790 |
|
return StreamSupport.doubleStream |
791 |
|
(new RandomDoublesSpliterator |
792 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
810 |
|
*/ |
811 |
|
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
812 |
|
if (!(randomNumberOrigin < randomNumberBound)) |
813 |
< |
throw new IllegalArgumentException(BadRange); |
813 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
814 |
|
return StreamSupport.doubleStream |
815 |
|
(new RandomDoublesSpliterator |
816 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
825 |
|
* approach. The long and double versions of this class are |
826 |
|
* identical except for types. |
827 |
|
*/ |
828 |
< |
static final class RandomIntsSpliterator implements Spliterator.OfInt { |
828 |
> |
private static final class RandomIntsSpliterator |
829 |
> |
implements Spliterator.OfInt { |
830 |
|
final SplittableRandom rng; |
831 |
|
long index; |
832 |
|
final long fence; |
881 |
|
/** |
882 |
|
* Spliterator for long streams. |
883 |
|
*/ |
884 |
< |
static final class RandomLongsSpliterator implements Spliterator.OfLong { |
884 |
> |
private static final class RandomLongsSpliterator |
885 |
> |
implements Spliterator.OfLong { |
886 |
|
final SplittableRandom rng; |
887 |
|
long index; |
888 |
|
final long fence; |
938 |
|
/** |
939 |
|
* Spliterator for double streams. |
940 |
|
*/ |
941 |
< |
static final class RandomDoublesSpliterator implements Spliterator.OfDouble { |
941 |
> |
private static final class RandomDoublesSpliterator |
942 |
> |
implements Spliterator.OfDouble { |
943 |
|
final SplittableRandom rng; |
944 |
|
long index; |
945 |
|
final long fence; |