烦请老师指正和提出改进意见～

老师我写了两种，但是不知道哪个更符合作业要求，我猜测作业应该有个隐含条件：每人三次抽奖机会，但是一旦抽中了，剩余的抽奖机会就作废了。

第一种代码：

package imooc_redo_exercise;

import java.util.Scanner;

public class Exerccise8_2 {

	public static void main(String[] args) {
		System.out.println("Please enter the customer's total amount of spending:");
		Scanner sc = new Scanner(System.in);
		float sum = sc.nextFloat();
		if(sum >= 100.0) {
			System.out.println("Congratulations! You got the chance to win a prize!");
			for(int i = 1; i <= 3; i++) {
				int num = (int) (Math.random()*3 + 1);
				System.out.println("num=" + num);
				if (num == 1) {
					System.out.println("Congratulations! You got a keyboard!");break;
				}else if(num ==2) {
					System.out.println("Congratulations! You got a kettle!");break;
				}else if(num ==3) {
					System.out.println("Congratulations! You got a souvenir!");break;
				}else {
					System.out.println("You got nothing! Wish you good luck next time");
				}
			}
		}else {
			System.out.println("Sorry! You are unqualified to participate in the activity!");

		}

	}

}

第二种代码：

​package imooc_redo_exercise;

import java.util.Scanner;

public class Exercise8_2_2 {

	public static void main(String[] args) {
		System.out.println("Please enter the customer's total amount of spending:");
		Scanner sc = new Scanner(System.in);
		float sum = sc.nextFloat();
		int i = 1;
		int num;
		if (sum >= 100.0) {
			System.out.println("Congratulations! You got the chance to win a prize!");

			do {
				num = (int) (Math.random() * 3 + 1);
				System.out.println("num=" + num);

				switch (num) {
				case 1:
					System.out.println("Congratulations! You got a keyboard!");

					break;
				case 2:
					System.out.println("Congratulations! You got a kettle!");

					break;
				case 3:
					System.out.println("Congratulations! You got a souvenir!");

					break;
				default:
					System.out.println("Congratulations! You got a souvenir!");

					break;
				}
				i++;
			} while ((i <= 3) && (num == 0));
		} else {
			System.out.println("Sorry! You are unqualified to participate in the activity!");

		}

	}

}