Question

I’m currently learning Java and learning while loop right now. How could I used the random() method to generate random negative number? Also, how do I make the program print out value that fall only in a certain range? For example Let say Java choose 10 random numbers, how could I make it so it only display number between 0.6 and 0.8?

 double randomNumber;
    int counter = 0;

    while(counter <= 99)
    {
        randomNumber = Math.random();
        System.out.println(randomNumber);
         counter++;

Answer 1

To get a random number in that range:

double r = Math.random(); // -> [0, 1)
r = r * 0.2;              // scale     -> [0, 0.2)
r = r + 0.6;              // translate -> [0.6, 0.8)

(Similar math can be done to create negative numbers or map to an arbitrary range.)

To “only do something” with a number if it is already in that range:

double r = Math.random(); // -> [0, 1)
if (r >= 0.6 && r < 0.8) {
    // r -> [0.6, 0.8)
} else {
    // r -> not in above range
}