난수 만들기

1. Random 클래스
2. java.lang.Math 클래스
3. System.currentTimeMillis()

1. Random 클래스

import java.util.Random;

public class Solution {

		public static void main(String[] args) {
			
			
			Random r = new Random();
			int n=r.nextInt()%10;
			System.out.println(n);
			
			boolean f = r.nextBoolean();
			System.out.println(f);
			
			int n = r.nextInt();
			System.out.println(n);
			
			int n2 =r.nextInt(10)+1; //1~10
			System.out.println(n2);
		}
}

2. java.lang.Math 클래스

public class Solution {
	public static void main(String[] args) {
		double a =Math.random();
		System.out.println(a);
		int b = (int)(a*10);
		System.out.println(b);
	}
}

3. System.currentTimeMillis()

public class RandomTest {
	public static void main(String[] args) {
		long a =System.currentTimeMillis();
		System.out.println(a);
		long b = (int)(a%10);
		System.out.println(b);
	}
}