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How to use the Math.random() method in Java

Educative Answers Team

The Math.random() method returns a pseudorandom number of data type double. The range of this random number is given by the following limit:

0.0x<1.00.0\leq x <1.0
where xx is the random number.

This method belongs to the java.lang.Math class, so you need to import this class before implementing​ this method.

Using the code snippet below we can generate a random number of type double. Give it a try!

import java.lang.Math; //importing Math class in Java

class MyClass { 
  public static void main(String args[]) 
  { 
    double rand = Math.random(); // generating random number 
    System.out.println("Random Number: " + rand);  // Output is different everytime this code is executed 
  } 
} 
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Using random() method for a range

Mostly the random() method is used to generate random numbers between a specific range. Using this method, we define a method named randomWithRange, that returns an integer with a user-defined range.

int randomWithRange(int min, int max){
   int range = (max - min) + 1;     
   return (int)(Math.random() * range) + min;
}

Since the random() method produces a double number, we need to cast it in an integer, just as shown in the example below:

class MyClass {
  int randomWithRange(int min, int max){   //defining method for a random number generator

    int range = (max - min) + 1;     
    return (int)(Math.random() * range) + min;
  }  
  public static void main( String args[] ) {
    MyClass obj1=new MyClass();       // creating an object of MyClass
    int rand=obj1.randomWithRange(1,100); // range is from 1 to 100 
    System.out.println(rand);
  }
}

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random
java
math.random
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