Best way to generate Random numbers in Java | Beginners Guide
Math.random() - Quick & Simple, Random class - More control and performance, ThreadLocalRandom Class - For multi threaded applications
Getting straight to the point, to generate a random number in Java, you can use the java.util.Random class. Given below are some detailed methods which you can choose according to your application's complexity.
Using Random Class
Here's an example:
Random random = new Random(); //Instance of the Random class
int randomNumber = random.nextInt(100);
// Generates a random integer between 0 and 99
You can change the bound (Parameter of nextInt method, 100 in this example) to generate random numbers within a different range, and you can also use other methods provided by the
Random class to generate different types of random values, such as nextDouble(), nextFloat().
To generate a random integer between min and max(inclusive), you can use the following code:
random.nextInt(max - min) + min;
For example :
Random random = new Random();
int randomNumber = random.nextInt(100) + 1;
Math.random() is a simple way to generate a random double between 0 (inclusive) and 1 (exclusive).
int a = (int)Math.random() * (max - min + 1) + min
//to get int, use type casting
java.util.Random provides a more flexible and powerful way to generate random numbers. Here are a few reasons why
java.util.Random might be preferred over
java.util.Randomallows you to customize your random number generation by specifying a seed, which can be useful for testing and debugging. It also provides methods for generating random numbers of different data types (e.g., integers, longs, floats, and doubles).
Reproducibility: If you want to generate the same sequence of random numbers repeatedly, you can use the
java.util.Randomto specify a seed value. (See more on seed value below)
java.util.Randomis designed to be thread-safe, meaning that multiple threads can use the same instance of
Randomwithout interfering with each other.
Performance: In some cases, the
Randomclass can be faster than
Math.random()method uses an instance of
Randominternally, but it also does some additional calculations to scale the result to the desired range.
Using ThreadLocalRandom Class
It is a sub-class of the Random class. It has its seed, which cannot be changed.
The ThreadLocalRandom class provides better performance in multi-threaded applications it makes it easier for threads to access different random number generators and avoid getting in each other's way.
Note: Here I have not focused much on how to use Math.Random and ThreadLocalRandom.
A pseudorandom number is a number that appears to be random but is generated using a deterministic algorithm. It's not truly random because it doesn't depend on a random physical process, but for all practical purposes, it's unpredictable and appears random.
All the above-discussed methods generate pseudorandom numbers and not truly random numbers.
Math.random() vs Random Class vs ThreadLocalRandom Class
If you just need a quick and simple way to generate a random number,
Math.random() is likely enough. However, if you need more control over the generation process or a large number of random numbers for use in a performance-critical application,
java.util.Random is the better option and is suitable for both single-threaded and multi-threaded applications, and
ThreadLocalRandom class is recommended for use in multi-threaded applications due to its better performance.
Seed value :
In the context of random number generation, a seed value is an initial value used to initialize the random number generator. The seed value is used to determine the sequence of numbers generated by the random number generator.
The sequence of random numbers generated by a random number generator is a deterministic sequence of numbers, meaning that given the same seed value, the same sequence of random numbers will be generated every time.
The seed value can be any integer value. If you do not specify a seed value when you create a new instance of a random number generator, Java will use the current time as the default seed value, so you will get a different sequence of random numbers each time you run the program.