Java Programming/Basic Arithmetic/Random Numbers
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To generate random numbers the Math.random() method can be used, which returns a double, greater than or equal to 0.0 and less than 1.0.
The following code returns a random integer between n and m (where n <= randomNumber < m):
int randomNumber = n + (int)(Math.random() * ( m - n ));
Alternatively, the java.util.Random class provides methods for generating random booleans, bytes, floats, ints, longs and 'Gaussians' (doubles from a normal distribution with mean 0.0 and standard deviation 1.0). For example, the following code is equivalent to that above:
Random random = new Random(); int randomNumber = n + random.nextInt(m - n);
Or:
Random random = new Random(); int randomNumber = random.nextInt(500); // this will return a pseudorandom int between 0 and 499
As an example using random numbers, we can make a program that uses a Random object to simulate flipping a coin 20 times:
import java.util.Random; public class CoinFlipper { public static void main(String[] args) { final int TIMES_TO_FLIP = 20; // The number of times to flip the coin int heads = 0; int tails = 0; Random random = new Random(); // create a Random object for (int i = 0; i < TIMES_TO_FLIP; i++) { int result = random.nextInt(2); // 0 or 1 if (result == 1) { System.out.println("Heads"); heads++; } else { System.out.println("Tails"); tails++; } } System.out.println("There were " + heads + " heads and " + tails + " tails"); } }
which could create this output:
Heads Tails Tails Tails Heads Tails Heads Heads Heads Heads Heads Heads Tails Tails Tails Tails Heads Tails Tails Tails There were 9 heads and 11 tails
Of course, if you run the program you will probably get different results.
