一.迴圈結構
1.while迴圈結構:

while( 迴圈條件 ){
迴圈操作內容
}

2. do while 迴圈結構:
   跟while 結構反過來，先寫操作內容，再寫迴圈條件

do{
迴圈操作內容
}
while( 迴圈條件 )

二.課後作業
1.計算100以內的偶數之和
package zyl;

public class Demo {
public static void main(String[] args) {
int num = 2;
int num2 = 0;
while(num<=100){
num2=num2+num;
num=num+2;

        	System.out.println("偶數的總數和是:"+num2);
        	
        } 
 

}}

2.升級購物結算
package ZYL;

import java.util.Scanner;

public class Demo {
public static void main(String[] args) {
int bianhao = 0;
int shuliang = 0;
String name ="";
double je = 0.0;
double hj = 0.0;
String a =“y”;

	System.out.println("MyShopping管理系統>購物結算");
	System.out.println("***************************************************");
    System.out.println("請選擇購買的商品編號:");
    System.out.println("1.T恤      2.網球鞋    3.網球拍");
    System.out.println("***************************************************");
    
    Scanner scanner = new Scanner(System.in);
      
    while("y".equals(a)){
    	System.out.print("請輸入產品編號:");
    	   bianhao = scanner.nextInt();
    	   
    	   switch(bianhao){
    	   case 1:
    		  name = "T恤";
    		  je = 245.0;
    		break;
    	   
    	   case 2:
    		  name = "網球鞋";
    		  je =455.0;
    		break;
    		
    	   case 3:
    		   name = "網球拍";
    		   je = 635.0;
    		break;
    		default:
    			System.out.println("沒有此選項");
    	   
    	   }    System.out.print("請輸入產品數量:");
    	      shuliang = scanner.nextInt();
    	      
    	      System.out.println(name+je+"                  "+"數量"+shuliang+"                       "+shuliang*je);
    	      hj = hj+shuliang*je;
    	     
    	   System.out.print("是否繼續(y/n)");
    	      a = scanner.next();
    	      while("y".equals(a)){System.out.print("請輸入產品編號:");
	    	   bianhao = scanner.nextInt();
	    	   
	    	   switch(bianhao){
	    	   case 1:
	    		  name = "T恤";
	    		  je = 245.0;
	    		break;
	    	   
	    	   case 2:
	    		  name = "網球鞋";
	    		  je =455.0;
	    		break;
	    		
	    	   case 3:
	    		   name = "網球拍";
	    		   je = 635.0;
	    		break;
	    		default:
	    			System.out.println("沒有此選項");   }    
	    	   
	    	   System.out.print("請輸入產品數量:");
	    	      shuliang = scanner.nextInt();
	    	      
	    	      System.out.println(name+je+"                  "+"數量"+shuliang+"                       "+shuliang*je);
	    	      hj = hj+shuliang*je;
	    	     
	    	   System.out.print("是否繼續(y/n)");
	    	      a = scanner.next();     }     }
               

            System.out.println("折扣0.8");

            System.out.println("應付金額:"+hj*0.8);
            
            System.out.print("實付金額:");
             double yingfu = scanner.nextDouble();
            
            
            System.out.println("找錢:"+(yingfu-hj*0.8));
}
}
 

3.攝氏度和華氏度
package ZYL;

public class Demo2 {
public static void main(String[] args) {
double centigrade = 0;
double fahrenheit = 0;
int tiaomu = 1;

          do{   centigrade = centigrade+20;
        	    fahrenheit = centigrade*9/5.0+32;
          
                System.out.println("攝氏度是:"+centigrade+"等於華氏度:"+fahrenheit);  
                tiaomu++;}  
          while(tiaomu<=10&&centigrade<=250);    }
 

}

4.升級選單切換
package ZYL;

import java.util.Scanner;

public class Demo3 {

public static void main(String[] args) {
	     System.out.println("歡迎使用Myshopping管理系統");
	     System.out.println("");
	     System.out.println("*********************************************************");
	     System.out.println("1.客戶資訊管理");
         System.out.println("2.購物結算");
         System.out.println("3.真情回饋");
         System.out.println("4.登出");
         System.out.println("*********************************************************");
         System.out.println("");
	Scanner scanner = new Scanner(System.in);
	    System.out.println("請選擇，輸入數字:");
	     int figure= scanner.nextInt();
	        do{
	        	System.out.println("輸入錯誤，請重新輸入:");
	        	 figure=scanner.nextInt();
	        } while(figure>4);
	        
	        System.out.println("執行購物結算");
	        System.out.println("");
	        System.out.println("程式結束");

5.教材第三章習題
1.package ZYL;

import java.util.Scanner;

public class Demo4 {
public static void main(String[] args) {
int figure;
Scanner scanner = new Scanner(System.in);

	  do{  
		   System.out.print("請輸入一個整數(輸入0結束):");
		    figure = scanner.nextInt();
		   
	   } while(figure>0);
	
	System.out.print("最大值是:");
	    int a =scanner.nextInt();
	System.out.print("最小值是:");
	    int b =scanner.nextInt();
}

}

package ZYL;

import java.util.Scanner;

public class Demo5 {
public static void main(String[] args) {
int figure;
Scanner scanner =new Scanner(System.in);
do {
System.out.print(“請輸入數字1-7(輸入0結束):”);
figure = scanner.nextInt();

	    	   switch(figure){
	    	   case 1:
	    		   System.out.println("今天表示MON");
	    		   break;
	    	   case 2:
	    		   System.out.println("今天表示TUE");
	    		   break;
	    	   case 3:
	    		   System.out.println("今天表示WED");
	    	       break;
	    	   case 4:
	    		   System.out.println("今天表示THU");
	    		   break;
	    	   case 5:
	    		   System.out.println("今天表示FRI");
	    		   break;
	    	   case 6:
	    		   System.out.println("今天表示SAT");
	    		   break;
	    	   case 7:
	    		   System.out.println("今天表示SUN");
	    		   
	    	   }  } while(figure>0) ;
	    	 
	    	System.out.println("程式結束");
}

}
3.
package ZYL;

import java.util.Scanner;

public class Demo6 {
public static void main(String[] args) {

	Scanner scanner = new Scanner(System.in);
	System.out.print("請輸入您出行的身份:1-12:");
	int time = scanner.nextInt();

	if (time <= 12 && time > 10) {
		System.out.print("請選擇您選擇頭等艙還是經濟艙？頭等艙輸入1，經濟艙輸入2:");
		int room = scanner.nextInt();
		if (room == 1) {
			System.out.println("您的機票價格為:" + 5000 * 0.5);
		}
		if (room == 2) {
			System.out.println("您的機票價格為:" + 5000 * 0.4);
		}
	}

	if (time <= 10 && time >= 4) {
		System.out.print("請選擇您選擇頭等艙還是經濟艙？頭等艙輸入1，經濟艙輸入2:");
		int room = scanner.nextInt();
		if (room == 1) {
			System.out.println("您的機票價格為:" + 5000 * 0.9);
		}
		if (room == 2) {
			System.out.println("您的機票價格為:" + 5000 * 0.6);
		}
	}
	if (time < 4) {
		System.out.print("請選擇您選擇頭等艙還是經濟艙？頭等艙輸入1，經濟艙輸入2:");
		int room = scanner.nextInt();
		if (room == 1) {
			System.out.println("您的機票價格為:" + 5000 * 0.5);
		}
		if (room == 2) {
			System.out.println("您的機票價格為:" + 5000 * 0.4);
		}
	}

}

}