package test;
import java.lang.Math;
import java.util.Scanner;

public class test1 {
    public static void main(String[] args) {
        while (true) {
            Scanner input = new Scanner(System.in);
            System.out.print("請(qǐng)輸入一個(gè)整數(shù)：");
            double rand_num = (Math.random()*(input.nextInt()-1)+1);
            System.out.println(rand_num);
        }
    }
}
//has 1 warning:
//Resource leak: 'input' is never closed
//解析：倘若在while循環(huán)內(nèi)添加input.close();第二次循環(huán)報(bào)錯(cuò)，scanner在循環(huán)中不會(huì)重復(fù)初始化，僅重復(fù)賦值

//解決方法：使用do...while而非while(true)
package test;
import java.lang.Math;
import java.util.Scanner;

public class test1 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        do {
            System.out.print("請(qǐng)輸入一個(gè)整數(shù)：");
            double rand_num = (Math.random()*(input.nextInt()-1)+1);
            System.out.println(rand_num);
        } while (input.hasNextInt());
        input.close();
    }
}