Question

我已经在这个问题上工作了好几个小时，但是无法理解。我通过用户输入获取字符串变量并将其与数组中的值进行比较。当数组中存在值时，第一个if语句执行正常。但是，无论该值是否存在，第二个if语句在执行时只应在数组中不存在该值时执行。

// begin the calculate() function on the condition that XXX is not typed
  while (addIn.compareTo("XXX") != 0) {

      for (x = 0; x < NUM_ITEMS; x++) {

          if (addIn.compareTo(addIns[x]) == 0) {
             System.out.println("The price of " + addIn + " is $" + addInPrices[x]);
             orderTotal += addInPrices[x];
          }

          if (addIn.compareTo(addIns[x]) != 0) {
              System.out.println("Sorry, we don't carry that.");
              addIn = JOptionPane.showInputDialog("Enter coffee add-in or " + END + " to quit: ");
          }

     }

     addIn = JOptionPane.showInputDialog("Enter your next add-in, or XXX to complete your order!");
 }

 System.out.println("Your total is $" + orderTotal + ". Your order will be out shortly!");

我做错了什么？

Answer 1

您正在为数组中的每个非匹配项执行第二条语句。你需要做的是设置一个标志并在循环结束时检查它：

// begin the calculate() function on the condition that XXX is not typed
while (addIn.compareTo("XXX") != 0) {

    boolean found = false;
    for (x = 0; x < NUM_ITEMS; x++) {
        if (addIn.compareTo(addIns[x]) == 0) {
            found = true;
            System.out.println("The price of " + addIn + " is $" + addInPrices[x]);
            orderTotal += addInPrices[x];
            break;
        }
    }

    if (!found) {
        System.out.println("Sorry, we don't carry that.");
        addIn = JOptionPane.showInputDialog("Enter coffee add-in or " + END + " to quit: ");
    } else {
        addIn = JOptionPane.showInputDialog("Enter your next add-in, or XXX to complete your order!");
    }
}

CompareTo方法 - 如何使用它与不相等？

1 个答案: