Java Math random() Method

The Math.random() method in Java is used to generate a pseudorandom double value that is greater than or equal to 0.0 and less than 1.0. Internally, this method uses a single instance of java.util.Random to produce random values, making it suitable for basic random number generation tasks. It does not require object creation (static method.

class GFG {
    public static void main(String[] args) {

        double value = Math.random();
        System.out.println(value);
    }
}

0.4504830241585366

Explanation: Math.random() generates a decimal value between 0.0 (inclusive) and 1.0 (exclusive). The returned value is stored in value and printed directly.

Syntax of random()

public static double random()

Return Type: "double" a pseudorandom value ≥ 0.0 and < 1.0.

Example 1: Generate a Random Double Value

The Math.random() produces a different decimal value on each execution.

class Gfg{
    public static void main(String[] args) {
        double rand = Math.random();
        System.out.println("Random Number: " + rand);
    }
}

Random Number: 0.2338390927184536

Explanation: Math.random() returns a pseudorandom double. Since no seed is manually provided, the value changes on every execution.

Example 2: Generate Random Integers Within a Fixed Range

Now to get random integer numbers from a given fixed range, we take a min and max variable to define the range for our random numbers, both min and max are inclusive in the range.

class Gfg{
    public static void main(String[] args) {
        int min = 1;
        int max = 10;
        int range = max - min + 1;

        for (int i = 0; i < 10; i++) {
            int rand = (int)(Math.random() * range) + min;
            System.out.println(rand);
        }
    }
}

8
3
10
2
5
4
4
7
5
6

Explanation:

• Math.random() * range scales the random value to the required range size.
• Casting to int removes the decimal part.
• Adding min shifts the value to start from the desired minimum.

To generate random integers in a range: (int)(Math.random() * (max - min + 1)) + min

Note:

• Math.random() is not suitable for cryptographic purposes.
• For better randomness and control, use java.util.Random or SecureRandom.
• The method always returns values less than 1.0, never equal to 1.0.