该程序的目的是显示笔记本电脑列表，并要求用户购买列出的一台或多台笔记本电脑。
我对在哪里以及如何循环使用此方法感到困惑。如果会做一会儿吗？
A）使用while循环处理给定购买的多台笔记本电脑。使用哨兵控制的循环变量。1）否则将找出笔记本电脑的名称/价格或打印“无效的选择！请重试”消息。3）如果是，则在笔记本电脑选择有效时嵌套，以继续进行其余的处理。
B]如果，则嵌套以仅在实际购买笔记本电脑时打印订单摘要。
C）将printf（）与格式说明符一起使用。
D）orderSummary是您已经声明并填充标头信息的String变量。现在，您将购买的每台笔记本电脑（订单项）添加到该标题信息中。使用+ =添加orderSummary中已经存在的内容。
到目前为止，除了使所有用户正确输入所需的循环外，我基本上拥有的所有代码。如果是我的第一个卡住的地方。
import java.util.Calendar;
import java.util.Scanner;
public class RamosS006PA1 {
public static void main(String[] args) {
char cont='Y';
int qty=0;
int trigger;
double total=0;
double subtotal=0;
double tax=0;
double price;
double lineItem;
String orderSummary=" ";
String laptop;
Scanner input = new Scanner(System.in);
Calendar dateTime = Calendar.getInstance();
//Displays a list of laptops with prices and asked user for their choice. Prompt #1
System.out.printf("%nTHE TOP LAPTOPS OF %tY"
+ "%n%n1. %-23s %7s $%,9.2f"
+ "%n2. %-23s %8s %,9.2f"
+ "%n3. %-23s %8s %,9.2f"
+ "%n4. %-23s %8s %,9.2f"
+ "%n5. %-23s %8s %,9.2f"
+ "%n%nEnter your choice: ",
dateTime,
"HP Envy 13", " ", 799.99,
"Asus ZenBook 13 UX333FA", " ", 849.99,
"Dell XPS 13", " ", 989.99,
"Alienware Area 51-m", " ", 1999.99,
"Razer Blade Stealth", " ", 1299.00);
int choice = input.nextInt();
if (choice < 1 || choice > 5) {
System.out.printf("Invalid choice! Try again.%n%n"); //Prompt #2
System.out.printf("Enter 'Y' to add a laptop to your purchase or 'N' to exit: "); //Prompt #3
cont = input.nextLine().charAt(0);
}
//The following if-else prints a $ sign for the first line item
if(trigger == 1)
{
orderSummary += String.format("%n%, -9d %-30s %8s $%,17.2f",
qty, laptop, " ", lineItem);
trigger = 0;
} //End else for no $ sign
//The following statement prints the order summary of the laptops purchased.
//This should be done when there are no more laptops to process
if (choice > 0)
{
if (choice < 6) {
tax = subtotal * .0825;
total = subtotal + tax;
orderSummary += String.format("%n%n%34s Subtotal %6s %,17.2f"
+ "%n%31s Tax @ 8.25%% %6s %,17.2f"
+ "%n%n%37s TOTAL %5s $%,17.2f%n",
" ", " ", subtotal,
" ", " ", tax,
" ", " ", total);
System.out.printf("%s", orderSummary);
} //End if valid choice range ends print order summary
} //End if valid choice range begins
}
}
您可以将整个（从打印到摘要放到一个循环中），并在显示购买摘要或用户输入要退出系统或循环的内容时中断循环。
int choice = 0;
while(choice >= 0){
//Displays a list of laptops with prices and asked user for their choice. Prompt #1
System.out.printf("%nTHE TOP LAPTOPS OF %tY"
+ "%n%n1. %-23s %7s $%,9.2f"
+ "%n2. %-23s %8s %,9.2f"
+ "%n3. %-23s %8s %,9.2f"
+ "%n4. %-23s %8s %,9.2f"
+ "%n5. %-23s %8s %,9.2f"
+ "%n%nEnter your choice: ",
dateTime,
"HP Envy 13", " ", 799.99,
"Asus ZenBook 13 UX333FA", " ", 849.99,
"Dell XPS 13", " ", 989.99,
"Alienware Area 51-m", " ", 1999.99,
"Razer Blade Stealth", " ", 1299.00);
choice = input.nextInt();
if (choice < 1 || choice > 5) {
System.out.printf("Invalid choice! Try again.%n%n"); //Prompt #2
System.out.printf("Enter 'Y' to add a laptop to your purchase or 'N' to exit: "); //Prompt #3
cont = input.nextLine().charAt(0);
}
//The following if-else prints a $ sign for the first line item
if(trigger == 1)
{
orderSummary += String.format("%n%, -9d %-30s %8s $%,17.2f",
qty, laptop, " ", lineItem);
trigger = 0;
} //End else for no $ sign
//The following statement prints the order summary of the laptops purchased.
//This should be done when there are no more laptops to process
if (choice > 0)
{
if (choice < 6)
{
tax = subtotal * .0825;
total = subtotal + tax;
orderSummary += String.format("%n%n%34s Subtotal %6s %,17.2f"
+ "%n%31s Tax @ 8.25%% %6s %,17.2f"
+ "%n%n%37s TOTAL %5s $%,17.2f%n",
" ", " ", subtotal,
" ", " ", tax,
" ", " ", total);
System.out.printf("%s", orderSummary);
break;
} //End if valid choice range ends print order summary
} //End if valid choice range begins
}
}
}