使用While循环代替Java中的For循环来询问用户输入 [英] Using While Loop instead of a For Loop in Java to ask User Input

问题描述

  Scanner askPrice = new Scanner（System.in）; 
 
 for（double i = 0; i <3; i ++）; 
 {
 double totalInitial = 0.00; 
 System.out.println（为您的物品输入价格。
 +每次输入后按回车键，不要输入'$'符号：）; 
 double price1 = askPrice.nextDouble（）; //输入价格one 
 double price2 = askPrice.nextDouble（）; //输入价格二
 double price3 = askPrice.nextDouble（）; //输入价格三
 
 double total =（（totalInitial）+（price1）+（price2）+（price3））; 
  

我想将for循环更改为while循环来询问用户物品的价格输入一个双精度值），直到定点值。我怎样才能做到这一点？我知道我已经设置了三个迭代，但是我想修改没有预设迭代次数的代码。任何帮助，将不胜感激。

解决方案

您可以试试这个：

  Scanner askPrice = new Scanner（System.in）; 
 //我们初始化一个拳头BigDecimal在0 
 BigDecimal totalPrice = new BigDecimal（0）; 
 //无限循环... 
 while（true）{
 // ...其中我们查询用户
 System.out.println（为您输入价格item。
 +每次输入后按回车键，不要输入'$'符号：）; 
 // ...尝试获取用户输入的下一个double 
 //并将其添加到总计
 try {
 double price = askPrice.nextDouble（）; 
 //这里是添加if语句来检查
 //用户输入的值（如果需要，中断）
 //  - 不正确的输入在 catch语句通过
 totalPrice = totalPrice.add（new BigDecimal（String.valueOf（price）））; 
 //这是一个很好的地方添加一个if语句来检查
 //总数和中断如有必要
} 
 // ...直到被意外破坏输入或任何其他异常
 catch（Throwable t）{
 //您应该根据
作出不同的反应//异常抛出
 System.out.println（finished -  TODO处理单个例外）; 
 //这打破了无限循环
 break; 
 
 
打印出最终结果
 System.out.println（totalPrice.toString（））; 
  

请注意 BigDecimal 的货币。

I wrote this piece of code:

Scanner askPrice = new Scanner(System.in);

for(double i = 0 ; i < 3; i++);
{
double totalInitial = 0.00;
System.out.println("Enter the price for your item. "
+ "Press enter after each entry. Do not type the '$' sign: ") ;
double price1 = askPrice.nextDouble(); //enter price one
double price2 = askPrice.nextDouble(); //enter price two
double price3 = askPrice.nextDouble(); //enter price three

double total = ((totalInitial) + (price1) + (price2) + (price3));

I want to change the for loop to a while loop to ask the user a price for an item (input of a double) until a sentinel value. How can I do this? I know I have three iterations already set, but I want to modify the code where there is not a preset number of iterations. Any help would be appreciated.

解决方案

You could try this:

Scanner askPrice = new Scanner(System.in);
// we initialize a fist BigDecimal at 0
BigDecimal totalPrice = new BigDecimal("0");
// infinite loop...
while (true) {
    // ...wherein we query the user
    System.out.println("Enter the price for your item. "
        + "Press enter after each entry. Do not type the '$' sign: ") ;
    // ... attempt to get the next double typed by user 
    // and add it to the total
    try {
        double price = askPrice.nextDouble();
            // here's a good place to add an "if" statement to check 
            // the value of user's input (and break if necessary) 
            // - incorrect inputs are handled in the "catch" statement though
        totalPrice = totalPrice.add(new BigDecimal(String.valueOf(price)));
            // here's a good place to add an "if" statement to check
            // the total and break if necessary
    }
    // ... until broken by an unexpected input, or any other exception
    catch (Throwable t) {
            // you should probably react differently according to the 
            // Exception thrown
        System.out.println("finished - TODO handle single exceptions");
            // this breaks the infinite loop
        break;
    }
}
// printing out final result
System.out.println(totalPrice.toString());

Note the BigDecimal here to better handle sums of currency.

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