The Random class in java.util provides methods to generate pseudo-random numbers of different types (int, long, float, double, boolean). Java also offers ThreadLocalRandom and SecureRandom for different use cases.
Scenarios
- Simulating games, lottery, or test data.
- Randomizing list items or shuffling arrays.
- Generating random IDs or temporary passwords.
- Using reproducible sequences of numbers with seeded randomness.
Sample Usage
import java.util.Random;
public class RandomExample {
public static void main(String[] args) {
Random rand = new Random(); // or new Random(seed)
int randomInt = rand.nextInt(100); // 0 to 99
double randomDouble = rand.nextDouble(); // 0.0 to 1.0
boolean randomBool = rand.nextBoolean();
System.out.println(randomInt);
System.out.println(randomDouble);
System.out.println(randomBool);
}
}
Better for concurrent use (Java 7+):
import java.util.concurrent.ThreadLocalRandom;
int randomInRange = ThreadLocalRandom.current().nextInt(10, 50); // 10 to 49
For cryptographically secure values:
import java.security.SecureRandom;
SecureRandom secure = new SecureRandom();
byte[] seed = new byte[16];
secure.nextBytes(seed); // fills the byte array with secure random values
Use Random for general purposes, ThreadLocalRandom for concurrent performance, and SecureRandom when security matters.