Learn to get a **Stream of random numbers** in Java using the *Random* and *SecureRandom* classes.

## 1. The `Random`

API

Java 8 release has added several methods to the `Random`

class which can return **a sequential stream of random numbers** (*integers*, *longs* and *doubles*). The most widely used methods are:

*IntStream***ints()***LongStream***longs()***DoubleStream***doubles()**

All of the above methods have their overloaded forms. For example, `ints()`

method has these overloaded forms.

*IntStream ints()*– Returns an effectively unlimited stream of pseudorandom`int`

values.*IntStream ints(long streamSize)*– Returns a stream producing the given number of pseudorandom`int`

values.*IntStream ints(int origin, int bound)*– Returns an effectively unlimited stream of`int`

values, each conforming to the given origin (inclusive) and bound (exclusive).*IntStream ints(long streamSize, int origin, int bound)*– Returns a stream producing the given number of pseudorandom`int`

values, each conforming to the given origin (inclusive) and bound (exclusive).

## 2. Example of Stream of Random Numbers

Let’s learn to use the above-discussed methods to create a stream of random numbers.

Random random = new Random(); //1 IntStream randStream = random.ints(5); randStream.forEach(System.out::println); //2 DoubleStream doubleStream = random.doubles(5, 0, 0.5); doubleStream.forEach(System.out::println); //collect to list List<Long> longs = random.longs(5) .boxed() .collect(Collectors.toList());

## 3. Stream of Secure Random Numbers

To get the stream of secure random numbers (i.e. cryptographically strong random number), use the subclass `SecureRandom`

. **By default, SecureRandom uses the SHA1PRNG algorithm.** The default constructor also uses this algorithm.

CSPRNG (cryptographically strong pseudo-random* number generator*) uses entropy, which is nothing but an unpredictable input (true random source). It might be a hardware random number generator or possibly some unpredictable system process, such as the timings events, interrupts etc.

```
SecureRandom secureRandomGenerator = SecureRandom.getInstanceStrong();
//1. Get 128 random bytes
byte[] randomBytes = new byte[128];
secureRandomGenerator.nextBytes(randomBytes);
//2. Get random integer
int r = secureRandomGenerator.nextInt();
//3. Get random integer in range
int randInRange = secureRandomGenerator.nextInt(999999);
```

Please note that all the above-discussed methods (*ints(), longs(), doubles() and their overloads*) also work with the `SecureRandom`

class.

```
SecureRandom sRand = SecureRandom.getInstanceStrong();
IntStream randStream = sRand.ints(5);
randStream.forEach(System.out::println);
```

Happy Learning !!

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