java将多个开关变量组合成一个字符串
我将创建一个显示完整收据（加上包含的所有项目）的程序但是，当选择两个相同的项目时，输出为： 4套餐价格 5套餐价格
而不是： 9套餐价格
可以合并两个相同的开关箱吗？我试过一个计数器，但仍然不起作用。我不知道这背后还有什么逻辑
import java.text.NumberFormat;
import java.util.Scanner;
public class Menu {
public static void main(String args []){
final double COFFEE= 1.8, SOFTDRINK = 2.0;
final double STARTER= 4.0, DESSERT= 3.5;
final double MAIN= 8.0;
final double COMBO1 = 11.0, COMBO2= 11.5, COMBO3 = 15.0;
double sum=0;
int item = 0, quantity=0;
int freeSoftDrink=0, freeCoffee=0;
String order="";
char decide= 'N';
boolean quit= false;
Scanner sc = new Scanner (System.in);
NumberFormat format= NumberFormat.getInstance();
format.setMaximumFractionDigits(2);
format.setMinimumFractionDigits(2);
do{
System.out.println("------------------ MENU ------------------");
System.out.println("ITEM"+"\t\t\t\tPRICE");
System.out.println("1.Coffee"+"\t\t\t"+"RM1.80");
System.out.println("2.Soft Drink"+"\t\t\t"+"RM2.00");
System.out.println("3.Dessert"+"\t\t\t"+"RM3.50");
System.out.println("4.Starter"+"\t\t\t"+"RM4.00");
System.out.println("5.Main Course"+"\t\t\t"+"RM8.00");
System.out.println("6.Main+Dessert"+"\t\t\t"+"RM11.00");
System.out.println("7.Main+Starter"+"\t\t\t"+"RM11.50");
System.out.println("8.Combo(Main+Starter+Dessert)"+"\t"+"RM15.00");
System.out.println("-----------------------------------------");
System.out.print("Select an item: ");
item = sc.nextInt();
if ((item<=8) && (item>=1)){
System.out.print("Enter quantity (1-50): ");
quantity = sc.nextInt();
}
while (((quantity<=0) || (quantity>=51)) && ((item<=8) && (item>=1)))
{
System.out.print("Invalid. Please re-enter quantity: ");
quantity = sc.nextInt();
}//end while
switch(item){
case 1:
System.out.println("You've ordered: "+quantity+" Coffee.\n");
sum=sum+(quantity*COFFEE);
order=order.concat(quantity +" Coffee\t\t\t"+"RM"
+format.format(quantity*COFFEE)+"\n");
break;
case 2:
System.out.println("You've ordered: "+quantity+" Soft Drink.\n");
sum=sum+(quantity*SOFTDRINK);
order=order.concat(quantity+" Soft Drink\t\t\t"+"RM"
+format.format(quantity*SOFTDRINK)+"\n");
break;
case 3:
System.out.println("You've ordered: "+quantity+" Dessert.\n");
sum=sum+(quantity*DESSERT);
order=order.concat(quantity+ " Dessert\t\t\t" +"RM"
+format.format(quantity*DESSERT)+"\n");
break;
case 4:
System.out.println("You've ordered: "+quantity+" Starter.\n");
sum=sum+(quantity*STARTER);
order=order.concat(quantity+" Starter\t\t\t"
+"RM"+format.format(quantity*STARTER)+"\n");
break;
case 5:
System.out.println("You've ordered: "+quantity+" Main.\n");
sum=sum+(quantity*MAIN);
order=order.concat(quantity+" Main\t\t\t\t" + "RM"
+format.format(quantity*MAIN)+"\n");
break;
case 6:
System.out.println("You've ordered: "+quantity+" Main+Dessert.\n");
sum=sum+(quantity*COMBO1);
order=order.concat(quantity+" Main+Dessert\t\t\t"
+"RM"+format.format(quantity*COMBO1)+"\n");
freeCoffee = freeCoffee + quantity;
break;
case 7:
System.out.println("You've ordered: "+quantity+" Main+Starter.\n");
sum=sum+(quantity*COMBO2);
order=order.concat(quantity+" Main+Starter\t\t\t"+"RM"
+format.format(quantity*COMBO2)+"\n");
freeSoftDrink = freeSoftDrink + quantity;
break;
case 8:
System.out.println("You've ordered: "+ quantity+" Combo.\n");
sum=sum+(quantity*COMBO3);
order=order.concat(quantity+" Combo"+" \t\t\t"
+"RM"+format.format(quantity*COMBO3)+"\n");
freeSoftDrink = freeSoftDrink + quantity;
freeCoffee = freeCoffee + quantity;
break;
default:
System.out.println("Invalid item.");
}//end switch
System.out.println("Do you want anything else? [Y/N]");
decide= sc.next().charAt(0);
System.out.println("");
while ((decide!='N' && decide!='n') && (decide!='Y' && decide!='y')){
System.out.print("Invalid. Try again: ");
decide=sc.next().charAt(0);
System.out.println("");
}
if (decide=='N'|| decide =='n'){
quit=true;
}
}//end do
while(!quit);
System.out.println();
System.out.println("Orders");
System.out.println("--------------------------------------------");
System.out.print(order);
if (freeCoffee<=0){
System.out.print("");
}
else {
System.out.println("*free "+ freeCoffee + " coffee.");
}
if (freeCoffee<=0){
System.out.print("");
}
else{
System.out.println("*free "+ freeSoftDrink + " soft drinks.");
}
System.out.println("--------------------------------------------");
System.out.println ("Your total bill\t\t\tRM"+ format.format(sum));
System.out.println("--------------------------------------------");
}//end main
}//end class
# 1 楼答案
导致问题的具体原因是：
order=order.concat(quantity+"Main+Dessert\t\t\t"+"RM"+format.format(quantity*COMBO1)+"\n");每次新的组合出现时，它都会附加到字符串中，而不是添加到组合成本中（如果已经存在）
我能想到的一个可能的修复方法是，将每个项的状态存储在
HashMap中。因此，您的案例陈述将如下所示：然后您可以收集所有订单值并将其打印在收据中：
orderMap.entrySet().forEach(entry -> System.out.println(entry.getKey() + ": " + entry.getValue);它将打印如下内容：