Java Math random() method

In this tutorial, we will learn everything about Java Math random() method. Java includes various library methods. The library methods or functions are the in-built methods provided to us which help us to perform our tasks easily, accurately, and quickly. These in-built functions are frequently used in Java. Math.random() method belongs to the in-built functions.

Math.random() in Java

Math random() method is included in the class Math under the package Java.lang. We can learn this in the form of cases:

First case:

It is the most general one. It is a method or function which returns a random number between 0 and 1 in a double data type value.

Syntax of the method:

<Return data type><variable>=<Function name()>;

In this way:

double d = Math.random();

This will return any random number generated between 0 and 1 to the variable d.

The complete code with user input using Scanner class:

import java.util.*;
public class Main
{
     public static void main(String args[])
     {
          Scanner in = new Scanner(System.in);
          double d;
          System.out.println("Random number between 0 and 1");
          d=Math.random();
          System.out.println(d);
     }
}

The output after executing the above code:

  Random number between 0 and 1

0.4402153460635767

Second case:

We can generate any random number between 1 and the upper limit provided by us. The upper limit is the value up to which the random number will be generated.

In this way:

double r = (double)(Math.random()*d)+1;

This will generate a random number between 1 and n and return the value to the variable r.

The complete code:

import java.util.*;
public class Main
{
     public static void main(String args[])
     {
          Scanner in = new Scanner(System.in);
          double d;
          System.out.println("Enter the upper limit");
          d=in.nextDouble();
          System.out.println("Random number between 0 and 1");
          double r = (double)(Math.random()*d)+1;
          System.out.println(r);
     }
}

The output after executing the above code:

  Enter the upper limit

6

Random number between 0 and 1

2.3983867459467447

Third case:

We can generate any random number between limits like m and n where m is the lower limit and n is the upper limit. Both the values can be provided by the user.

In this way:

double r = (double)(Math.random()*(n-m))+m;

This will generate a random number between m and n and will return the value to the variable r.

The complete code:

import java.util.*;
public class Main
{
     public static void main(String args[])
     {
          Scanner in = new Scanner(System.in);
          double m;
          System.out.println("Enter the lower limit");
          m=in.nextDouble();
          double n;
          System.out.println("Enter the upper limit");
          n=in.nextDouble();
          System.out.println("Random number between 0 and 1");
          double r = (double)(Math.random()*(n-m))+m;
          System.out.println(r);
     }
}

The output after executing the above code:

  Enter the lower limit

10

Enter the upper limit

20

Random number between 0 and 1

19.865869869904387

Hope this tutorial was useful.

Also read: Guess The Number Game Using Java with Source Code