Random random = new Random();
    System.out.println(20+random.nextInt(80));

/*
 * 计算 min <= ，<= max 的随即整数，取到范围内各整数的概率相等。
 */

import java.util.Random;

public class MathTool {

    private static Random rnd = null;

    private MathTool() {}

    public static int getRandom(int min, int max) {
        if (min == max) return min;
        if (min > max) {
            int t = min;
            min = max;
            max = t;
        }
        if (rnd == null) rnd = new Random();
        return rnd.nextInt(max - min + 1) + min;
    }

}