Java Program to Print Random Number

On this page, we are going to learn how to write a Java programme to print a random number.

We will use three different approaches to print a random number in Java as given below.

Program 1: Print random number using Random class

We need to create an instance of the java.util.Random class first and then call methods such as nextInt(), nextDouble(), nextLong(), etc. with the help of that instance. We can pass parameters to the methods for placing an upper bound on the range of the numbers to be generated. For example, nextInt(5) will generate numbers in the range of 0 to 4, both inclusive.

  
  import java.util.Random;
  public class RandomNumber {
    public static void main(String[] args) {
      Random rnum = new Random();
      
      // Generate 5 random numbers between 0 to 1000
      System.out.println("5 Random Numbers are:");
      System.out.println("===================");
      for (int i = 1; i <= 5; i++) {
        // Print random number
        System.out.println(rnum.nextInt(1000));
      }
    }
  }

Program 2: Print random number using Math.random() method

The Math class is a class of the lang package. It contains many methods to perform different operations. It has a method that prints the random number. That method's name is the random() method. This method returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0. The returned values are chosen pseudorandomly.

  public class RandomNumber2 {
    public static void main(String[] args) {
      // Generating random number
          System.out.println("Random number: " + Math.random());
    }
  }

Program 3: Print random number using ThreadLocalRandom class

The ThreadLocalRandom class was introduced in the Java 1.7 version and placed in the java.util.concurrent package. This class can generate random numbers of types such as integers, doubles, booleans, etc.

  
  import java.util.concurrent.ThreadLocalRandom;
  public class RandomNumber3 {
    public static void main(String[] args) {
      
      // Generate random integer number
      System.out.println("Random Integer 1: " + ThreadLocalRandom.current().nextInt());
      System.out.println("Random Integer 2: " + ThreadLocalRandom.current().nextInt());
      System.out.println("Random Integer 3: " + ThreadLocalRandom.current().nextInt());
      
      // Generate random double number
      System.out.println("\nRandom Double 1: " + ThreadLocalRandom.current().nextDouble());
      System.out.println("Random Double 2: " + ThreadLocalRandom.current().nextDouble());
      System.out.println("Random Double 3: " + ThreadLocalRandom.current().nextDouble());
      
      // Generate random booleans
      System.out.println("\nRandom Boolean 1: " + ThreadLocalRandom.current().nextBoolean());
      System.out.println("Random Boolean 2: " + ThreadLocalRandom.current().nextBoolean());
      System.out.println("Random Boolean 3: " + ThreadLocalRandom.current().nextBoolean());
    }
  }

Random Integer 1: -1503823616
Random Integer 2: -1345710525
Random Integer 3: -1818189431

Random Double 1: 0.5139741611423724
Random Double 2: 0.0833277782528794
Random Double 3: 0.5313404603108741

Random Boolean 1: true
Random Boolean 2: false
Random Boolean 3: false