Java - Math random() method

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Description

The Java Math random() returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0.

Returned values are chosen pseudorandomly with (approximately) uniform distribution from that range. When this method is first called, it creates a single new pseudorandom-number generator, exactly as if by the expression new java.util.Random

This new pseudorandom-number generator is used thereafter for all calls to this method and is used nowhere else. This method is properly synchronized to allow correct use by more than one thread. However, if many threads need to generate pseudorandom numbers at a great rate, it may reduce contention for each thread to have its own pseudorandom-number generator.

Declaration

Following is the declaration for java.lang.Math.random() method

public static double random()

Parameters

NA

Return Value

This method returns a pseudorandom double greater than or equal to 0.0 and less than 1.0.

Exception

NA

Example: Getting Random Number between 0.0 and 1.0

The following example shows the usage of Math random() method to get a random number between 0.0 and 1.0.

package com.tutorialspoint;
public class MathDemo {
   public static void main(String[] args) {

      // get two random double numbers
      double x = Math.random();
      double y = Math.random();
   
      // print the numbers and print the higher one
      System.out.println("Random number 1:" + x);
      System.out.println("Random number 2:" + y);
      System.out.println("Highest number:" + Math.max(x, y));
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Random number 1:0.5016301836409477
Random number 2:0.591827364722481
Highest number:0.591827364722481

Example: Getting Random Number between 0.0 and 5.0

The following example shows the usage of Math random() method to get a random number between 0.0 and 5.0.

package com.tutorialspoint;
public class MathDemo {
   public static void main(String[] args) {

      // get two random double numbers
      double x = Math.random() * 5.0;
      double y = Math.random() * 5.0;
   
      // print the numbers and print the higher one
      System.out.println("Random number 1:" + x);
      System.out.println("Random number 2:" + y);
      System.out.println("Highest number:" + Math.max(x, y));
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Random number 1:2.9497714055410174
Random number 2:1.1016708521940748
Highest number:2.9497714055410174

Example: Getting Random Number between 0.0 and -5.0

The following example shows the usage of Math random() method to get a random number between 0.0 and -5.0.

package com.tutorialspoint;
public class MathDemo {
   public static void main(String[] args) {

      // get two random double numbers
      double x = Math.random() * -5.0;
      double y = Math.random() * -5.0;
   
      // print the numbers and print the higher one
      System.out.println("Random number 1:" + x);
      System.out.println("Random number 2:" + y);
      System.out.println("Highest number:" + Math.max(x, y));
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Random number 1:-4.597468918068065
Random number 2:-1.1033485127978726
Highest number:-1.1033485127978726