How to Generate Random Number Within a Specified Range in Java

1. Generate Random Number Using the ThreadLocalRandom Class in Java
2. Generate Random Number Using the Math Class in Java
3. Generate Random Number Using the Random Class in Java
4. Generate Random Number Using the Random Class in Java
5. Generate Random Number Using the Random Class and IntStream in Java
6. Generate Random Number Using the nextFloat Method in Java
7. Generate Random Number Using the RandomData Class in Java
8. Generate Random Number Using SecureRandom Class in Java
9. Generate Random Number Using the RandomUtils Class in Java

This tutorial introduces how to generate a random number within a specified range in Java.

There are several ways to generate random number in Java, such as the nextInt() method of the ThreadLocalRandom class, the random() method of the Math class, the nextInt() method of the Random class, the ints() method of the Random class, the nextFloat() method of the Random class and the RandomUtil class, etc.

Generate Random Number Using the ThreadLocalRandom Class in Java

Java concurrent package provides a class ThreadLocalRandom that has the nextInt() method. This method can generate a random integer within the specified range. See the below example.

import java.util.concurrent.ThreadLocalRandom;

public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    ThreadLocalRandom tlr = ThreadLocalRandom.current();
    int randomNum = tlr.nextInt(min_val, max_val + 1);
    System.out.println("Random Number: " + randomNum);
  }
}

Output:

Value in double: 12.9
Value in int: 12

Generate Random Number Using the Math Class in Java

Java Math class can be used to generate a random number within the specified range. Here, we use the random() method of the Math class to get a random number. See the example below.

public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    double randomNum = Math.random() * (max_val - min_val);
    System.out.println("Random Number: " + randomNum);
  }
}

Output:

Id: 1212
Name: Samre

Generate Random Number Using the Random Class in Java

The Random class of Java can generate a random integer within the specified range by using the nextInt() method, which returns an integer value. See the example below.

import java.util.Random;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    Random ran = new Random();
    int x = ran.nextInt(max_val) + min_val;
    System.out.println("Random Number: " + x);
  }
}

Output:

Id: 1212
Name: Samre

Generate Random Number Using the Random Class in Java

This is another solution for getting a random integer within the specified range. Here, we use the nextInt() method of the Random class with different parameters. See the example below.

import java.util.Random;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    Random rand = new Random();
    int randomNum = min_val + rand.nextInt((max_val - min_val) + 1);
    System.out.println("Random Number: " + randomNum);
  }
}

Output:

Random Number: 75

Generate Random Number Using the Random Class and IntStream in Java

Here, we use the ints() method of the Random class that returns a stream of random numbers. We use the forEach() method to print all the random integers generated by the ints() method. See the below example.

import java.util.Random;
import java.util.stream.IntStream;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    Random rand = new Random();
    IntStream stream = rand.ints(5, min_val, max_val);
    stream.forEach(System.out::println);
  }
}

Output:

94
35
90
74
47

Generate Random Number Using the nextFloat Method in Java

The Random class provides a method nextFloat() to generate a float type random number. If we want to get a float-type random number, then this method is useful. See the below example.

import java.util.Random;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    Random rand = new Random();
    float rand_val = rand.nextFloat() * (max_val - min_val);
    System.out.println(rand_val);
  }
}

Output:

71.88764

Generate Random Number Using the RandomData Class in Java

If you are working with the apache commons library, then use the RandomData class. This class provides a method nextInt() that returns an integer value. We can use this method to generate random integers within the specified range. See the example below.

import org.apache.commons.math.random.RandomData;
import org.apache.commons.math.random.RandomDataImpl;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    RandomData randomData randomData = new RandomDataImpl();
    int number = randomData.nextInt(min_val, max_val);
    System.out.println(number);
  }
}

Output:

72

Generate Random Number Using SecureRandom Class in Java

The SecureRandom class belongs to the security package of Java that is used to create a secure random number. Here, we use the Date class to generate a seed and then the nextInt() method to generate a random integer. See the below example.

import java.security.SecureRandom;
import java.util.Date;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    SecureRandom rand = new SecureRandom();
    rand.setSeed(new Date().getTime());
    int randomNum = rand.nextInt((max_val - min_val) + 1) + min_val;
    System.out.println(randomNum);
  }
}

Output:

65

Generate Random Number Using the RandomUtils Class in Java

We can use the RandomUtil class of the apache commons library to generate random integers. The nextInt() method of this class returns an integer class. See the below example.

import org.apache.commons.lang3.RandomUtils;
public class SimpleTesting {
  public static void main(String[] args) {
    int min_val = 10;
    int max_val = 100;
    RandomUtils random = new RandomUtils();
    int randomNum = random.nextInt(min_val, max_val);
    System.out.println(randomNum);
  }
}

Output:

66