Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Ctors](https://developer.android.com/reference/java/util/Random#pubctors) \| [Methods](https://developer.android.com/reference/java/util/Random#pubmethods) \| [Protected Methods](https://developer.android.com/reference/java/util/Random#promethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/Random#inhmethods)
# Random
` public class Random `
` extends https://developer.android.com/reference/java/lang/Object ` ` implements https://developer.android.com/reference/java/util/random/RandomGenerator, https://developer.android.com/reference/java/io/Serializable `
|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | java.util.Random |
Known direct subclasses [SecureRandom](https://developer.android.com/reference/java/security/SecureRandom), [ThreadLocalRandom](https://developer.android.com/reference/java/util/concurrent/ThreadLocalRandom) [SecureRandom](https://developer.android.com/reference/java/security/SecureRandom) This class provides a cryptographically strong random number generator (RNG). [ThreadLocalRandom](https://developer.android.com/reference/java/util/concurrent/ThreadLocalRandom) A random number generator (with period 2^64^) isolated to the current thread.
*** ** * ** ***
An instance of this class is used to generate a stream of pseudorandom numbers; its period is only 2^48^. The class uses a 48-bit seed, which is modified using a linear congruential formula. (See Donald E. Knuth, The Art of Computer Programming, Volume 2, Third edition: Seminumerical Algorithms, Section 3.2.1.)
If two instances of `Random` are created with the same seed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers. In order to guarantee this property, particular algorithms are specified for the class `Random`. Java implementations must use all the algorithms shown here for the class `Random`, for the sake of absolute portability of Java code. However, subclasses of class `Random` are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.
The algorithms implemented by class `Random` use a `protected` utility method that on each invocation can supply up to 32 pseudorandomly generated bits.
Many applications will find the method `https://developer.android.com/reference/java/lang/Math#random()` simpler to use.
Instances of `java.util.Random` are threadsafe. However, the concurrent use of the same `java.util.Random` instance across threads may encounter contention and consequent poor performance. Consider instead using `https://developer.android.com/reference/java/util/concurrent/ThreadLocalRandom` in multithreaded designs.
Instances of `java.util.Random` are not cryptographically secure. Consider instead using `https://developer.android.com/reference/java/security/SecureRandom` to get a cryptographically secure pseudo-random number generator for use by security-sensitive applications.
## Summary
| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/java/util/Random#Random()() ` Creates a new random number generator. |
| ` https://developer.android.com/reference/java/util/Random#Random(long)(long seed) ` Creates a new random number generator using a single `long` seed. |
| ### Public methods ||
|---|---|
| ` https://developer.android.com/reference/java/util/stream/DoubleStream` | ` https://developer.android.com/reference/java/util/Random#doubles(long)(long streamSize) ` Returns a stream producing the given `streamSize` number of pseudorandom `double` values, each between zero (inclusive) and one (exclusive). |
| ` https://developer.android.com/reference/java/util/stream/DoubleStream` | ` https://developer.android.com/reference/java/util/Random#doubles()() ` Returns an effectively unlimited stream of pseudorandom `double` values, each between zero (inclusive) and one (exclusive). |
| ` https://developer.android.com/reference/java/util/stream/DoubleStream` | ` https://developer.android.com/reference/java/util/Random#doubles(double,%20double)(double randomNumberOrigin, double randomNumberBound) ` Returns an effectively unlimited stream of pseudorandom `double` values, each conforming to the given origin (inclusive) and bound (exclusive). |
| ` https://developer.android.com/reference/java/util/stream/DoubleStream` | ` https://developer.android.com/reference/java/util/Random#doubles(long,%20double,%20double)(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). |
| ` static https://developer.android.com/reference/java/util/Random` | ` https://developer.android.com/reference/java/util/Random#from(java.util.random.RandomGenerator)(https://developer.android.com/reference/java/util/random/RandomGenerator generator) ` Returns an instance of `Random` that delegates method calls to the `https://developer.android.com/reference/java/util/random/RandomGenerator` argument. |
| ` https://developer.android.com/reference/java/util/stream/IntStream` | ` https://developer.android.com/reference/java/util/Random#ints(long)(long streamSize) ` Returns a stream producing the given `streamSize` number of pseudorandom `int` values. |
| ` https://developer.android.com/reference/java/util/stream/IntStream` | ` https://developer.android.com/reference/java/util/Random#ints(int,%20int)(int randomNumberOrigin, int randomNumberBound) ` Returns an effectively unlimited stream of pseudorandom `int` values, each conforming to the given origin (inclusive) and bound (exclusive). |
| ` https://developer.android.com/reference/java/util/stream/IntStream` | ` https://developer.android.com/reference/java/util/Random#ints(long,%20int,%20int)(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). |
| ` https://developer.android.com/reference/java/util/stream/IntStream` | ` https://developer.android.com/reference/java/util/Random#ints()() ` Returns an effectively unlimited stream of pseudorandom `int` values. |
| ` https://developer.android.com/reference/java/util/stream/LongStream` | ` https://developer.android.com/reference/java/util/Random#longs()() ` Returns an effectively unlimited stream of pseudorandom `long` values. |
| ` https://developer.android.com/reference/java/util/stream/LongStream` | ` https://developer.android.com/reference/java/util/Random#longs(long)(long streamSize) ` Returns a stream producing the given `streamSize` number of pseudorandom `long` values. |
| ` https://developer.android.com/reference/java/util/stream/LongStream` | ` https://developer.android.com/reference/java/util/Random#longs(long,%20long)(long randomNumberOrigin, long randomNumberBound) ` Returns an effectively unlimited stream of pseudorandom `long` values, each conforming to the given origin (inclusive) and bound (exclusive). |
| ` https://developer.android.com/reference/java/util/stream/LongStream` | ` https://developer.android.com/reference/java/util/Random#longs(long,%20long,%20long)(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` | ` https://developer.android.com/reference/java/util/Random#nextBoolean()() ` Returns the next pseudorandom, uniformly distributed `boolean` value from this random number generator's sequence. |
| ` void` | ` https://developer.android.com/reference/java/util/Random#nextBytes(byte[])(byte[] bytes) ` Generates random bytes and places them into a user-supplied byte array. |
| ` double` | ` https://developer.android.com/reference/java/util/Random#nextDouble()() ` Returns the next pseudorandom, uniformly distributed `double` value between `0.0` and `1.0` from this random number generator's sequence. |
| ` float` | ` https://developer.android.com/reference/java/util/Random#nextFloat()() ` Returns the next pseudorandom, uniformly distributed `float` value between `0.0` and `1.0` from this random number generator's sequence. |
| ` double` | ` https://developer.android.com/reference/java/util/Random#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` | ` https://developer.android.com/reference/java/util/Random#nextInt()() ` Returns the next pseudorandom, uniformly distributed `int` value from this random number generator's sequence. |
| ` int` | ` https://developer.android.com/reference/java/util/Random#nextInt(int)(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` | ` https://developer.android.com/reference/java/util/Random#nextLong()() ` Returns the next pseudorandom, uniformly distributed `long` value from this random number generator's sequence. |
| ` void` | ` https://developer.android.com/reference/java/util/Random#setSeed(long)(long seed) ` Sets or updates the seed of this random number generator using the provided `long` seed value (optional operation). |
| ### Protected methods ||
|---|---|
| ` int` | ` https://developer.android.com/reference/java/util/Random#next(int)(int bits) ` Generates the next pseudorandom number. |
### Inherited methods
From class ` https://developer.android.com/reference/java/lang/Object ` ` https://developer.android.com/reference/java/lang/Object` ` https://developer.android.com/reference/java/lang/Object#clone()() `
Creates and returns a copy of this object.
` boolean` ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) `
Indicates whether some other object is "equal to" this one.
` void` ` https://developer.android.com/reference/java/lang/Object#finalize()() `
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
` final https://developer.android.com/reference/java/lang/Class` ` https://developer.android.com/reference/java/lang/Object#getClass()() `
Returns the runtime class of this `Object`.
` int` ` https://developer.android.com/reference/java/lang/Object#hashCode()() `
Returns a hash code value for the object.
` final void` ` https://developer.android.com/reference/java/lang/Object#notify()() `
Wakes up a single thread that is waiting on this object's monitor.
` final void` ` https://developer.android.com/reference/java/lang/Object#notifyAll()() `
Wakes up all threads that are waiting on this object's monitor.
` https://developer.android.com/reference/java/lang/String` ` https://developer.android.com/reference/java/lang/Object#toString()() `
Returns a string representation of the object.
` final void` ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) `
Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed.
` final void` ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) `
Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed.
` final void` ` https://developer.android.com/reference/java/lang/Object#wait()() `
Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*.
From interface ` https://developer.android.com/reference/java/util/random/RandomGenerator ` ` default https://developer.android.com/reference/java/util/stream/DoubleStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#doubles(long,%20double,%20double)(long streamSize, double randomNumberOrigin, double randomNumberBound) `
Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
` default https://developer.android.com/reference/java/util/stream/DoubleStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#doubles(long)(long streamSize) `
Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values.
` default https://developer.android.com/reference/java/util/stream/DoubleStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#doubles()() `
Returns an effectively unlimited stream of pseudorandomly chosen `double` values.
` default https://developer.android.com/reference/java/util/stream/DoubleStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#doubles(double,%20double)(double randomNumberOrigin, double randomNumberBound) `
Returns an effectively unlimited stream of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
` default https://developer.android.com/reference/java/util/stream/DoubleStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#equiDoubles(double,%20double,%20boolean,%20boolean)(double left, double right, boolean isLeftIncluded, boolean isRightIncluded) `
Returns an effectively unlimited stream of pseudorandomly chosen `double` values, where each value is between the specified `left` boundary and the specified `right` boundary.
` static https://developer.android.com/reference/java/util/random/RandomGenerator` ` https://developer.android.com/reference/java/util/random/RandomGenerator#getDefault()() `
Returns a `https://developer.android.com/reference/java/util/random/RandomGenerator` meeting the minimal requirement of having an [algorithm](https://developer.android.com/reference/java/util/package-summary#algorithms) whose state bits are greater than or equal 64.
` default https://developer.android.com/reference/java/util/stream/IntStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#ints(long)(long streamSize) `
Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values.
` default https://developer.android.com/reference/java/util/stream/IntStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#ints(int,%20int)(int randomNumberOrigin, int randomNumberBound) `
Returns an effectively unlimited stream of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
` default https://developer.android.com/reference/java/util/stream/IntStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#ints()() `
Returns an effectively unlimited stream of pseudorandomly chosen `int` values.
` default https://developer.android.com/reference/java/util/stream/IntStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#ints(long,%20int,%20int)(long streamSize, int randomNumberOrigin, int randomNumberBound) `
Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
` default boolean` ` https://developer.android.com/reference/java/util/random/RandomGenerator#isDeprecated()() `
Return true if the implementation of RandomGenerator (algorithm) has been marked for deprecation.
` default https://developer.android.com/reference/java/util/stream/LongStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#longs(long)(long streamSize) `
Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values.
` default https://developer.android.com/reference/java/util/stream/LongStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#longs()() `
Returns an effectively unlimited stream of pseudorandomly chosen `long` values.
` default https://developer.android.com/reference/java/util/stream/LongStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#longs(long,%20long)(long randomNumberOrigin, long randomNumberBound) `
Returns an effectively unlimited stream of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
` default https://developer.android.com/reference/java/util/stream/LongStream` ` https://developer.android.com/reference/java/util/random/RandomGenerator#longs(long,%20long,%20long)(long streamSize, long randomNumberOrigin, long randomNumberBound) `
Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
` default boolean` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextBoolean()() `
Returns a pseudorandomly chosen `boolean` value.
` default void` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextBytes(byte[])(byte[] bytes) `
Fills a user-supplied byte array with generated byte values pseudorandomly chosen uniformly from the range of values between -128 (inclusive) and 127 (inclusive).
` default double` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextDouble()() `
Returns a pseudorandom `double` value between zero (inclusive) and one (exclusive).
` default double` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextDouble(double)(double bound) `
Returns a pseudorandomly chosen `double` value between zero (inclusive) and the specified bound (exclusive).
` default double` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextDouble(double,%20double)(double origin, double bound) `
Returns a pseudorandomly chosen `double` value between the specified origin (inclusive) and the specified bound (exclusive).
` default double` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextExponential()() `
Returns a nonnegative `double` value pseudorandomly chosen from an exponential distribution whose mean is 1.
` default float` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextFloat(float,%20float)(float origin, float bound) `
Returns a pseudorandomly chosen `float` value between the specified origin (inclusive) and the specified bound (exclusive).
` default float` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextFloat()() `
Returns a pseudorandom `float` value between zero (inclusive) and one (exclusive).
` default float` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextFloat(float)(float bound) `
Returns a pseudorandomly chosen `float` value between zero (inclusive) and the specified bound (exclusive).
` default double` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextGaussian(double,%20double)(double mean, double stddev) `
Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution with a mean and standard deviation specified by the arguments.
` default double` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextGaussian()() `
Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution whose mean is 0 and whose standard deviation is 1.
` default int` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextInt(int,%20int)(int origin, int bound) `
Returns a pseudorandomly chosen `int` value between the specified origin (inclusive) and the specified bound (exclusive).
` default int` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextInt()() `
Returns a pseudorandomly chosen `int` value.
` default int` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextInt(int)(int bound) `
Returns a pseudorandomly chosen `int` value between zero (inclusive) and the specified bound (exclusive).
` default long` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextLong(long,%20long)(long origin, long bound) `
Returns a pseudorandomly chosen `long` value between the specified origin (inclusive) and the specified bound (exclusive).
` default long` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextLong(long)(long bound) `
Returns a pseudorandomly chosen `long` value between zero (inclusive) and the specified bound (exclusive).
` abstract long` ` https://developer.android.com/reference/java/util/random/RandomGenerator#nextLong()() `
Returns a pseudorandomly chosen `long` value.
` static https://developer.android.com/reference/java/util/random/RandomGenerator` ` https://developer.android.com/reference/java/util/random/RandomGenerator#of(java.lang.String)(https://developer.android.com/reference/java/lang/String name) `
Returns an instance of `https://developer.android.com/reference/java/util/random/RandomGenerator` that utilizes the `name` [algorithm](https://developer.android.com/reference/java/util/package-summary#algorithms).
## Public constructors
### Random
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public Random ()
```
Creates a new random number generator. This constructor sets the seed of the random number generator to a value very likely to be distinct from any other invocation of this constructor.
### Random
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public Random (long seed)
```
Creates a new random number generator using a single `long` seed. The seed is the initial value of the internal state of the pseudorandom number generator which is maintained by method `https://developer.android.com/reference/java/util/Random#next(int)`.
##### Implementation Requirements:
- The invocation `new Random(seed)` is equivalent to:
Random rnd = new Random();
rnd.setSeed(seed);
| Parameters ||
|---|---|
| `seed` | `long`: the initial seed
|
**See also:**
- `https://developer.android.com/reference/java/util/Random#setSeed(long)`
## Public methods
### doubles
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public DoubleStream doubles (long streamSize)
```
Returns a stream producing the given `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 `https://developer.android.com/reference/java/util/Random#nextDouble()`.
| Parameters ||
|---|---|
| `streamSize` | `long`: the number of values to generate
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/DoubleStream` | a stream of `double` values
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `streamSize` is less than zero |
### doubles
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public DoubleStream doubles ()
```
Returns an effectively unlimited stream 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 `https://developer.android.com/reference/java/util/Random#nextDouble()`.
##### Implementation Note:
- This method is implemented to be equivalent to `doubles(Long.MAX_VALUE)`.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/DoubleStream` | a stream of pseudorandom `double` values
|
### doubles
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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).
##### Implementation Note:
- This method is implemented to be equivalent to `doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)`.
| Parameters ||
|---|---|
| `randomNumberOrigin` | `double`: the origin (inclusive) of each random value
|
| `randomNumberBound` | `double`: the bound (exclusive) of each random value
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/DoubleStream` | a stream of pseudorandom `double` values, each with the given origin (inclusive) and bound (exclusive)
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | |
### doubles
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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).
| Parameters ||
|---|---|
| `streamSize` | `long`: the number of values to generate
|
| `randomNumberOrigin` | `double`: the origin (inclusive) of each random value
|
| `randomNumberBound` | `double`: the bound (exclusive) of each random value
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/DoubleStream` | a stream of pseudorandom `double` values, each with the given origin (inclusive) and bound (exclusive)
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | |
### from
Added in [API level 36](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public static Random from (RandomGenerator generator)
```
Returns an instance of `Random` that delegates method calls to the `https://developer.android.com/reference/java/util/random/RandomGenerator` argument. If the generator is an instance of `Random`, it is returned. Otherwise, this method returns an instance of `Random` that delegates all methods except `setSeed` to the generator. The returned instance's `setSeed` method always throws `https://developer.android.com/reference/java/lang/UnsupportedOperationException`. The returned instance is not serializable.
| Parameters ||
|---|---|
| `generator` | `RandomGenerator`: the `RandomGenerator` calls are delegated to
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Random` | the delegating `Random` instance
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if generator is null |
### ints
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public IntStream ints (long streamSize)
```
Returns a stream producing the given `streamSize` number of pseudorandom `int` values.
A pseudorandom `int` value is generated as if it's the result of calling the method `https://developer.android.com/reference/java/util/Random#nextInt()`.
| Parameters ||
|---|---|
| `streamSize` | `long`: the number of values to generate
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/IntStream` | a stream of pseudorandom `int` values
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `streamSize` is less than zero |
### ints
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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).
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;
}
}
##### Implementation Note:
- This method is implemented to be equivalent to `ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)`.
| Parameters ||
|---|---|
| `randomNumberOrigin` | `int`: the origin (inclusive) of each random value
|
| `randomNumberBound` | `int`: the bound (exclusive) of each random value
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/IntStream` | a stream of pseudorandom `int` values, each with the given origin (inclusive) and bound (exclusive)
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `randomNumberOrigin` is greater than or equal to `randomNumberBound` |
### ints
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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).
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;
}
}
| Parameters ||
|---|---|
| `streamSize` | `long`: the number of values to generate
|
| `randomNumberOrigin` | `int`: the origin (inclusive) of each random value
|
| `randomNumberBound` | `int`: the bound (exclusive) of each random value
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/IntStream` | a stream of pseudorandom `int` values, each with the given origin (inclusive) and bound (exclusive)
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `streamSize` is less than zero, or `randomNumberOrigin` is greater than or equal to `randomNumberBound` |
### ints
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public IntStream ints ()
```
Returns an effectively unlimited stream of pseudorandom `int` values.
A pseudorandom `int` value is generated as if it's the result of calling the method `https://developer.android.com/reference/java/util/Random#nextInt()`.
##### Implementation Note:
- This method is implemented to be equivalent to `ints(Long.MAX_VALUE)`.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/IntStream` | a stream of pseudorandom `int` values
|
### longs
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public LongStream longs ()
```
Returns an effectively unlimited stream of pseudorandom `long` values.
A pseudorandom `long` value is generated as if it's the result of calling the method `https://developer.android.com/reference/java/util/Random#nextLong()`.
##### Implementation Note:
- This method is implemented to be equivalent to `longs(Long.MAX_VALUE)`.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/LongStream` | a stream of pseudorandom `long` values
|
### longs
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public LongStream longs (long streamSize)
```
Returns a stream producing the given `streamSize` number of pseudorandom `long` values.
A pseudorandom `long` value is generated as if it's the result of calling the method `https://developer.android.com/reference/java/util/Random#nextLong()`.
| Parameters ||
|---|---|
| `streamSize` | `long`: the number of values to generate
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/LongStream` | a stream of pseudorandom `long` values
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `streamSize` is less than zero |
### longs
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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).
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;
}
##### Implementation Note:
- This method is implemented to be equivalent to `longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)`.
| Parameters ||
|---|---|
| `randomNumberOrigin` | `long`: the origin (inclusive) of each random value
|
| `randomNumberBound` | `long`: the bound (exclusive) of each random value
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/LongStream` | a stream of pseudorandom `long` values, each with the given origin (inclusive) and bound (exclusive)
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `randomNumberOrigin` is greater than or equal to `randomNumberBound` |
### longs
Added in [API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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).
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;
}
| Parameters ||
|---|---|
| `streamSize` | `long`: the number of values to generate
|
| `randomNumberOrigin` | `long`: the origin (inclusive) of each random value
|
| `randomNumberBound` | `long`: the bound (exclusive) of each random value
|
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/stream/LongStream` | a stream of pseudorandom `long` values, each with the given origin (inclusive) and bound (exclusive)
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if `streamSize` is less than zero, or `randomNumberOrigin` is greater than or equal to `randomNumberBound` |
### nextBoolean
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public boolean nextBoolean ()
```
Returns the next pseudorandom, uniformly distributed `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.
##### Implementation Requirements:
- The method `nextBoolean` is implemented by class `Random` as if by:
public boolean nextBoolean() {
return next(1) != 0;
}
| Returns ||
|---|---|
| `boolean` | the next pseudorandom, uniformly distributed `boolean` value from this random number generator's sequence
|
### nextBytes
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public void nextBytes (byte[] bytes)
```
Generates random bytes and places them into a user-supplied byte array. The number of random bytes produced is equal to the length of the byte array.
##### Implementation Requirements:
- 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;
}
| Parameters ||
|---|---|
| `bytes` | `byte`: the byte array to fill with random bytes
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the byte array is null |
### nextDouble
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public double nextDouble ()
```
Returns the next pseudorandom, uniformly distributed `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.
##### Implementation Requirements:
- 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.
\[In early versions of Java, the result was incorrectly calculated as:
return (((long)next(27) << 27) + next(27)) / (double)(1L << 54);
This might seem to be equivalent, if not better, but in fact it introduced a large nonuniformity because of the bias in the rounding of floating-point numbers: it was three times as likely that the low-order bit of the significand would be 0 than that it would be 1! This nonuniformity probably doesn't matter much in practice, but we strive for perfection.\]
| Returns ||
|---|---|
| `double` | the next pseudorandom, uniformly distributed `double` value between `0.0` and `1.0` from this random number generator's sequence
|
**See also:**
- `https://developer.android.com/reference/java/lang/Math#random()`
### nextFloat
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public float nextFloat ()
```
Returns the next pseudorandom, uniformly distributed `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 2^24^ possible `float` values of the form *m x *2^-24^, where *m* is a positive integer less than 2^24^, are produced with (approximately) equal probability.
##### Implementation Requirements:
- 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.
\[In early versions of Java, the result was incorrectly calculated as:
return next(30) / ((float)(1 << 30));
This might seem to be equivalent, if not better, but in fact it introduced a slight nonuniformity because of the bias in the rounding of floating-point numbers: it was slightly more likely that the low-order bit of the significand would be 0 than that it would be 1.\]
| Returns ||
|---|---|
| `float` | the next pseudorandom, uniformly distributed `float` value between `0.0f` and `1.0f` from this random number generator's sequence
|
### nextGaussian
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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.
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.
##### Implementation Requirements:
- 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 2, third edition: 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`.
| Returns ||
|---|---|
| `double` | the next pseudorandom, Gaussian ("normally") distributed `double` value with mean `0.0` and standard deviation `1.0` from this random number generator's sequence
|
### nextInt
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public int nextInt ()
```
Returns the next pseudorandom, uniformly distributed `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 2^32^ possible `int` values are produced with (approximately) equal probability.
##### Implementation Requirements:
- The method `nextInt` is implemented by class `Random` as if by:
public int nextInt() {
return next(32);
}
| Returns ||
|---|---|
| `int` | the next pseudorandom, uniformly distributed `int` value from this random number generator's sequence
|
### nextInt
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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. 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.
##### Implementation Requirements:
- 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.
| Parameters ||
|---|---|
| `bound` | `int`: the upper bound (exclusive). Must be positive.
|
| Returns ||
|---|---|
| `int` | the next pseudorandom, uniformly distributed `int` value between zero (inclusive) and `bound` (exclusive) from this random number generator's sequence
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if bound is not positive |
### nextLong
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public long nextLong ()
```
Returns the next pseudorandom, uniformly distributed `long` value from this random number generator's sequence. The general contract of `nextLong` is that one `long` value is pseudorandomly generated and returned.
##### Implementation Requirements:
- 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.
| Returns ||
|---|---|
| `long` | the next pseudorandom, uniformly distributed `long` value from this random number generator's sequence
|
### setSeed
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public void setSeed (long seed)
```
Sets or updates the seed of this random number generator using the provided `long` seed value (optional operation).
##### Implementation Requirements:
- The implementation in this class alters the state of this random number generator so that it is in the same state as if it had just been created with `https://developer.android.com/reference/java/util/Random#Random(long)`. It atomically updates the seed to
(seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)
and clears the `haveNextNextGaussian` flag used by `https://developer.android.com/reference/java/util/Random#nextGaussian()`. Note that this uses only 48 bits of the given seed value.
| Parameters ||
|---|---|
| `seed` | `long`: the seed value
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if the `setSeed` operation is not supported by this random number generator |
## Protected methods
### next
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected int next (int bits)
```
Generates the next pseudorandom number. This method returns an `int` value such that, if the argument `bits` is between `1` and `32` (inclusive), then that many low-order bits of the returned value will be (approximately) independently chosen bit values, each of which is (approximately) equally likely to be `0` or `1`.
##### API Note:
- The other random-producing methods in this class are implemented in terms of this method, so subclasses can override just this method to provide a different source of pseudorandom numbers for the entire class.
##### Implementation Requirements:
- The implementation in this class atomically updates the seed to
(seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)
and returns
(int)(seed >>> (48 - bits)).
This is a linear congruential pseudorandom number generator, as defined by D. H. Lehmer and described by Donald E. Knuth in The Art of Computer Programming, Volume 2, Third edition: Seminumerical Algorithms, section 3.2.1.
| Parameters ||
|---|---|
| `bits` | `int`: random bits
|
| Returns ||
|---|---|
| `int` | the next pseudorandom value from this random number generator's sequence
|