充分利用switch-case 中break的特性，更方便的求出天數。

要點： 月份倒著寫，並且每個case 不要新增break；那麼，程式就會一直往下執行，直到month=1，進而求出了總的天數。

以下是原始碼：

package third;

import java.util.Scanner;

public class dataRequire {

static int  require(int month, int day, boolean f){
    int sum=0;

    switch (month-1) {

        case 11:
            sum = sum +30;
        case 10:
            sum = sum +31;
        case 9:
            sum = sum +30;
        case 8:
            sum = sum +31;
        case 7:
            sum = sum +31;
        case 6:
            sum = sum +30;
        case 5:
            sum = sum +31;
        case 4:
            sum = sum +30;
        case 3:
            sum = sum +31;
        case 2:
            {if ( f)
                sum = sum +28;
            else 
                sum = sum +29;
            }
        case 1:
            sum = sum +31;
            break;
    }
    return sum+day ;


}
public static void main(String[] args) {
    // TODO Auto-generated method stub

    int year, day, month;
    boolean f =false;
    System.out.println("請輸入年月日：");
    Scanner sc = new Scanner(System.in);
    year = sc.nextInt();
    month = sc.nextInt();
    day = sc.nextInt();


    if ( year %4 ==0 && year%100!=0 || year%400 ==0)
        f = true;


    int sum = require(month,day, f);
    System.out.println("是第"+sum+"天");

}
 

}