| Constructor and Description |
|---|
WrappedRandom(java.util.Random wrapped) |
| Modifier and Type | Method and Description |
|---|---|
java.util.stream.DoubleStream |
doubles()
Returns an effectively unlimited stream of pseudorandom
double values, each between zero (inclusive) and one
(exclusive). |
java.util.stream.DoubleStream |
doubles(double randomNumberOrigin,
double randomNumberBound)
Returns an effectively unlimited stream of pseudorandom
double values, each conforming to the given origin (inclusive) and bound
(exclusive). |
java.util.stream.DoubleStream |
doubles(long streamSize)
Returns a stream producing the given
streamSize number of
pseudorandom double values, each between zero
(inclusive) and one (exclusive). |
java.util.stream.DoubleStream |
doubles(long streamSize,
double randomNumberOrigin,
double randomNumberBound)
Returns a stream producing the given
streamSize number of
pseudorandom double values, each conforming to the given origin
(inclusive) and bound (exclusive). |
long |
getSeed()
Returns the initial seed used to create this object.
|
java.util.stream.IntStream |
ints()
Returns an effectively unlimited stream of pseudorandom
int
values. |
java.util.stream.IntStream |
ints(int randomNumberOrigin,
int randomNumberBound)
Returns an effectively unlimited stream of pseudorandom
int values, each conforming to the given origin (inclusive) and bound
(exclusive). |
java.util.stream.IntStream |
ints(long streamSize)
Returns a stream producing the given
streamSize number of
pseudorandom int values. |
java.util.stream.IntStream |
ints(long streamSize,
int randomNumberOrigin,
int randomNumberBound)
Returns a stream producing the given
streamSize number
of pseudorandom int values, each conforming to the given
origin (inclusive) and bound (exclusive). |
java.util.stream.LongStream |
longs()
Returns an effectively unlimited stream of pseudorandom
long
values. |
java.util.stream.LongStream |
longs(long streamSize)
Returns a stream producing the given
streamSize number of
pseudorandom long values. |
java.util.stream.LongStream |
longs(long randomNumberOrigin,
long randomNumberBound)
Returns an effectively unlimited stream of pseudorandom
long values, each conforming to the given origin (inclusive) and bound
(exclusive). |
java.util.stream.LongStream |
longs(long streamSize,
long randomNumberOrigin,
long randomNumberBound)
Returns a stream producing the given
streamSize number of
pseudorandom long, each conforming to the given origin
(inclusive) and bound (exclusive). |
boolean |
nextBoolean()
Returns the next pseudorandom, uniformly distributed
boolean value from this random number generator's
sequence. |
void |
nextBytes(byte[] bytes)
Generates random bytes and places them into a user-supplied
byte array.
|
double |
nextDouble()
Returns the next pseudorandom, uniformly distributed
double value between 0.0 and
1.0 from this random number generator's sequence. |
float |
nextFloat()
Returns the next pseudorandom, uniformly distributed
float
value between 0.0 and 1.0 from this random
number generator's sequence. |
double |
nextGaussian()
Returns the next pseudorandom, Gaussian ("normally") distributed
double value with mean 0.0 and standard
deviation 1.0 from this random number generator's sequence. |
int |
nextInt()
Returns the next pseudorandom, uniformly distributed
int
value from this random number generator's sequence. |
int |
nextInt(int bound)
Returns a pseudorandom, uniformly distributed
int value
between 0 (inclusive) and the specified value (exclusive), drawn from
this random number generator's sequence. |
long |
nextLong()
Returns the next pseudorandom, uniformly distributed
long
value from this random number generator's sequence. |
void |
setSeed(long seed)
Sets the seed of this random number generator using a single
long seed. |
public java.util.stream.DoubleStream doubles(long streamSize)
streamSize number of
pseudorandom double values, each between zero
(inclusive) and one (exclusive).
A pseudorandom double value is generated as if it's the result
of calling the method nextDouble().
public java.util.stream.DoubleStream doubles()
double values, each between zero (inclusive) and one
(exclusive).
A pseudorandom double value is generated as if it's the result
of calling the method nextDouble().
public java.util.stream.DoubleStream doubles(long streamSize,
double randomNumberOrigin,
double randomNumberBound)
streamSize number of
pseudorandom double values, each conforming to the given origin
(inclusive) and bound (exclusive).
A pseudorandom double value is generated as if it's the result
of calling the following method with the origin and bound:
double nextDouble(double origin, double bound) {
double r = nextDouble();
r = r * (bound - origin) + origin;
if (r >= bound) // correct for rounding
r = Math.nextDown(bound);
return r;
}doubles in interface IRandomstreamSize - the number of values to generaterandomNumberOrigin - the origin (inclusive) of each random valuerandomNumberBound - the bound (exclusive) of each random valuedouble values,
each with the given origin (inclusive) and bound (exclusive)java.lang.IllegalArgumentException - if streamSize is
less than zerojava.lang.IllegalArgumentException - if randomNumberOrigin
is greater than or equal to randomNumberBoundpublic java.util.stream.DoubleStream doubles(double randomNumberOrigin,
double randomNumberBound)
double values, each conforming to the given origin (inclusive) and bound
(exclusive).
A pseudorandom double value is generated as if it's the result
of calling the following method with the origin and bound:
double nextDouble(double origin, double bound) {
double r = nextDouble();
r = r * (bound - origin) + origin;
if (r >= bound) // correct for rounding
r = Math.nextDown(bound);
return r;
}doubles in interface IRandomrandomNumberOrigin - the origin (inclusive) of each random valuerandomNumberBound - the bound (exclusive) of each random valuedouble values,
each with the given origin (inclusive) and bound (exclusive)java.lang.IllegalArgumentException - if randomNumberOrigin
is greater than or equal to randomNumberBoundpublic long getSeed()
public void setSeed(long seed)
long seed. The general contract of setSeed is
that it alters the state of this random number generator object
so as to be in exactly the same state as if it had just been
created with the argument seed as a seed. The method
setSeed is implemented by class Random by
atomically updating the seed to
(seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)haveNextNextGaussian flag used by nextGaussian().
The implementation of setSeed by class Random
happens to use only 48 bits of the given seed. In general, however,
an overriding method may use all 64 bits of the long
argument as a seed value.
public java.util.stream.IntStream ints(long streamSize)
streamSize number of
pseudorandom int values.
A pseudorandom int value is generated as if it's the result of
calling the method nextInt().
public java.util.stream.IntStream ints()
int
values.
A pseudorandom int value is generated as if it's the result of
calling the method nextInt().
public java.util.stream.IntStream ints(long streamSize,
int randomNumberOrigin,
int randomNumberBound)
streamSize number
of pseudorandom int values, each conforming to the given
origin (inclusive) and bound (exclusive).
A pseudorandom int value is generated as if it's the result of
calling the following method with the origin and bound:
int nextInt(int origin, int bound) {
int n = bound - origin;
if (n > 0) {
return nextInt(n) + origin;
}
else { // range not representable as int
int r;
do {
r = nextInt();
} while (r < origin || r >= bound);
return r;
}
}ints in interface IRandomstreamSize - the number of values to generaterandomNumberOrigin - the origin (inclusive) of each random valuerandomNumberBound - the bound (exclusive) of each random valueint values,
each with the given origin (inclusive) and bound (exclusive)java.lang.IllegalArgumentException - if streamSize is
less than zero, or randomNumberOrigin
is greater than or equal to randomNumberBoundpublic java.util.stream.IntStream ints(int randomNumberOrigin,
int randomNumberBound)
int values, each conforming to the given origin (inclusive) and bound
(exclusive).
A pseudorandom int value is generated as if it's the result of
calling the following method with the origin and bound:
int nextInt(int origin, int bound) {
int n = bound - origin;
if (n > 0) {
return nextInt(n) + origin;
}
else { // range not representable as int
int r;
do {
r = nextInt();
} while (r < origin || r >= bound);
return r;
}
}ints in interface IRandomrandomNumberOrigin - the origin (inclusive) of each random valuerandomNumberBound - the bound (exclusive) of each random valueint values,
each with the given origin (inclusive) and bound (exclusive)java.lang.IllegalArgumentException - if randomNumberOrigin
is greater than or equal to randomNumberBoundpublic java.util.stream.LongStream longs(long streamSize)
streamSize number of
pseudorandom long values.
A pseudorandom long value is generated as if it's the result
of calling the method nextLong().
public java.util.stream.LongStream longs()
long
values.
A pseudorandom long value is generated as if it's the result
of calling the method nextLong().
public java.util.stream.LongStream longs(long streamSize,
long randomNumberOrigin,
long randomNumberBound)
streamSize number of
pseudorandom long, each conforming to the given origin
(inclusive) and bound (exclusive).
A pseudorandom long value is generated as if it's the result
of calling the following method with the origin and bound:
long nextLong(long origin, long bound) {
long r = nextLong();
long n = bound - origin, m = n - 1;
if ((n & m) == 0L) // power of two
r = (r & m) + origin;
else if (n > 0L) { // reject over-represented candidates
for (long u = r >>> 1; // ensure nonnegative
u + m - (r = u % n) < 0L; // rejection check
u = nextLong() >>> 1) // retry
;
r += origin;
}
else { // range not representable as long
while (r < origin || r >= bound)
r = nextLong();
}
return r;
}longs in interface IRandomstreamSize - the number of values to generaterandomNumberOrigin - the origin (inclusive) of each random valuerandomNumberBound - the bound (exclusive) of each random valuelong values,
each with the given origin (inclusive) and bound (exclusive)java.lang.IllegalArgumentException - if streamSize is
less than zero, or randomNumberOrigin
is greater than or equal to randomNumberBoundpublic java.util.stream.LongStream longs(long randomNumberOrigin,
long randomNumberBound)
long values, each conforming to the given origin (inclusive) and bound
(exclusive).
A pseudorandom long value is generated as if it's the result
of calling the following method with the origin and bound:
long nextLong(long origin, long bound) {
long r = nextLong();
long n = bound - origin, m = n - 1;
if ((n & m) == 0L) // power of two
r = (r & m) + origin;
else if (n > 0L) { // reject over-represented candidates
for (long u = r >>> 1; // ensure nonnegative
u + m - (r = u % n) < 0L; // rejection check
u = nextLong() >>> 1) // retry
;
r += origin;
}
else { // range not representable as long
while (r < origin || r >= bound)
r = nextLong();
}
return r;
}longs in interface IRandomrandomNumberOrigin - the origin (inclusive) of each random valuerandomNumberBound - the bound (exclusive) of each random valuelong values,
each with the given origin (inclusive) and bound (exclusive)java.lang.IllegalArgumentException - if randomNumberOrigin
is greater than or equal to randomNumberBoundpublic boolean nextBoolean()
boolean value from this random number generator's
sequence. The general contract of nextBoolean is that one
boolean value is pseudorandomly generated and returned. The
values true and false are produced with
(approximately) equal probability.
The method nextBoolean is implemented by class Random
as if by:
public boolean nextBoolean() {
return next(1) != 0;
}nextBoolean in interface IRandomboolean value from this random number generator's
sequencepublic void nextBytes(byte[] bytes)
The method nextBytes is implemented by class Random
as if by:
public void nextBytes(byte[] bytes) {
for (int i = 0; i < bytes.length; )
for (int rnd = nextInt(), n = Math.min(bytes.length - i, 4);
n-- > 0; rnd >>= 8)
bytes[i++] = (byte)rnd;
}public double nextDouble()
double value between 0.0 and
1.0 from this random number generator's sequence.
The general contract of nextDouble is that one
double value, chosen (approximately) uniformly from the
range 0.0d (inclusive) to 1.0d (exclusive), is
pseudorandomly generated and returned.
The method nextDouble is implemented by class Random
as if by:
public double nextDouble() {
return (((long)next(26) << 27) + next(27))
/ (double)(1L << 53);
}
The hedge "approximately" is used in the foregoing description only
because the next method is only approximately an unbiased
source of independently chosen bits. If it were a perfect source of
randomly chosen bits, then the algorithm shown would choose
double values from the stated range with perfect uniformity.
[In early versions of Java, the result was incorrectly calculated as:
return (((long)next(27) << 27) + next(27))
/ (double)(1L << 54);
This might seem to be equivalent, if not better, but in fact it
introduced a large nonuniformity because of the bias in the rounding
of floating-point numbers: it was three times as likely that the
low-order bit of the significand would be 0 than that it would be 1!
This nonuniformity probably doesn't matter much in practice, but we
strive for perfection.]nextDouble in interface IRandomdouble
value between 0.0 and 1.0 from this
random number generator's sequenceMath.random()public float nextFloat()
float
value between 0.0 and 1.0 from this random
number generator's sequence.
The general contract of nextFloat is that one
float value, chosen (approximately) uniformly from the
range 0.0f (inclusive) to 1.0f (exclusive), is
pseudorandomly generated and returned. All 224 possible
float values of the form m x 2-24,
where m is a positive integer less than 224, are
produced with (approximately) equal probability.
The method nextFloat is implemented by class Random
as if by:
public float nextFloat() {
return next(24) / ((float)(1 << 24));
}
The hedge "approximately" is used in the foregoing description only
because the next method is only approximately an unbiased source of
independently chosen bits. If it were a perfect source of randomly
chosen bits, then the algorithm shown would choose float
values from the stated range with perfect uniformity.
[In early versions of Java, the result was incorrectly calculated as:
return next(30) / ((float)(1 << 30));
This might seem to be equivalent, if not better, but in fact it
introduced a slight nonuniformity because of the bias in the rounding
of floating-point numbers: it was slightly more likely that the
low-order bit of the significand would be 0 than that it would be 1.]public double nextGaussian()
double value with mean 0.0 and standard
deviation 1.0 from this random number generator's sequence.
The general contract of nextGaussian is that one
double value, chosen from (approximately) the usual
normal distribution with mean 0.0 and standard deviation
1.0, is pseudorandomly generated and returned.
The method nextGaussian is implemented by class
Random as if by a threadsafe version of the following:
private double nextNextGaussian;
private boolean haveNextNextGaussian = false;
public double nextGaussian() {
if (haveNextNextGaussian) {
haveNextNextGaussian = false;
return nextNextGaussian;
} else {
double v1, v2, s;
do {
v1 = 2 * nextDouble() - 1; // between -1.0 and 1.0
v2 = 2 * nextDouble() - 1; // between -1.0 and 1.0
s = v1 * v1 + v2 * v2;
} while (s >= 1 || s == 0);
double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
nextNextGaussian = v2 * multiplier;
haveNextNextGaussian = true;
return v1 * multiplier;
}
}
This uses the polar method of G. E. P. Box, M. E. Muller, and
G. Marsaglia, as described by Donald E. Knuth in The Art of
Computer Programming, Volume 3: Seminumerical Algorithms,
section 3.4.1, subsection C, algorithm P. Note that it generates two
independent values at the cost of only one call to StrictMath.log
and one call to StrictMath.sqrt.nextGaussian in interface IRandomdouble value with mean 0.0 and
standard deviation 1.0 from this random number
generator's sequencepublic int nextInt()
int
value from this random number generator's sequence. The general
contract of nextInt is that one int value is
pseudorandomly generated and returned. All 232 possible
int values are produced with (approximately) equal probability.
The method nextInt is implemented by class Random
as if by:
public int nextInt() {
return next(32);
}public int nextInt(int bound)
int value
between 0 (inclusive) and the specified value (exclusive), drawn from
this random number generator's sequence. The general contract of
nextInt is that one int value in the specified range
is pseudorandomly generated and returned. All bound possible
int values are produced with (approximately) equal
probability. The method nextInt(int bound) is implemented by
class Random as if by:
public int nextInt(int bound) {
if (bound <= 0)
throw new IllegalArgumentException("bound must be positive");
if ((bound & -bound) == bound) // i.e., bound is a power of 2
return (int)((bound * (long)next(31)) >> 31);
int bits, val;
do {
bits = next(31);
val = bits % bound;
} while (bits - val + (bound-1) < 0);
return val;
}
The hedge "approximately" is used in the foregoing description only
because the next method is only approximately an unbiased source of
independently chosen bits. If it were a perfect source of randomly
chosen bits, then the algorithm shown would choose int
values from the stated range with perfect uniformity.
The algorithm is slightly tricky. It rejects values that would result in an uneven distribution (due to the fact that 2^31 is not divisible by n). The probability of a value being rejected depends on n. The worst case is n=2^30+1, for which the probability of a reject is 1/2, and the expected number of iterations before the loop terminates is 2.
The algorithm treats the case where n is a power of two specially: it returns the correct number of high-order bits from the underlying pseudo-random number generator. In the absence of special treatment, the correct number of low-order bits would be returned. Linear congruential pseudo-random number generators such as the one implemented by this class are known to have short periods in the sequence of values of their low-order bits. Thus, this special case greatly increases the length of the sequence of values returned by successive calls to this method if n is a small power of two.
nextInt in interface IRandombound - the upper bound (exclusive). Must be positive.int
value between zero (inclusive) and bound (exclusive)
from this random number generator's sequencejava.lang.IllegalArgumentException - if bound is not positivepublic long nextLong()
long
value from this random number generator's sequence. The general
contract of nextLong is that one long value is
pseudorandomly generated and returned.
The method nextLong is implemented by class Random
as if by:
public long nextLong() {
return ((long)next(32) << 32) + next(32);
}
Because class Random uses a seed with only 48 bits,
this algorithm will not return all possible long values.