Java Random Number Generator

Upper bounds are exclusive in Java's random APIs, so add 1 to include the maximum.

import java.util.concurrent.ThreadLocalRandom;

int n = ThreadLocalRandom.current().nextInt(1, 11); // 1..10

import java.util.Random;

Random random = new Random();
int m = random.nextInt(10) + 1;                       // 1..10

nextDouble() returns a value in [0.0, 1.0).

double d = ThreadLocalRandom.current().nextDouble();          // 0.0 <= d < 1.0
double e = ThreadLocalRandom.current().nextDouble(1.5, 4.5);   // 1.5 <= e < 4.5

Pick by index, or shuffle a list with Collections.shuffle.

List<String> items = new ArrayList<>(List.of("red", "green", "blue"));
String pick = items.get(ThreadLocalRandom.current().nextInt(items.size()));
Collections.shuffle(items);                      // in place
Collections.shuffle(items, new SecureRandom());  // secure shuffle

java.util.Random is predictable. Use SecureRandom for passwords, tokens and draws - create it once and reuse it.

import java.security.SecureRandom;

SecureRandom secure = new SecureRandom();
int n = secure.nextInt(10) + 1;   // 1..10
byte[] token = new byte[16];
secure.nextBytes(token);

Math.abs(random.nextInt()) % n can return a negative number (the absolute value of Integer.MIN_VALUE is still negative) and is biased - use nextInt(n). Creating a new Random on every call wastes time; reuse one instance or use ThreadLocalRandom.