java - 使用 If 检查整数

Question

如何使用If来检查输入必须是整数并且不能输入任何英文单词。

int numWeight = sc.nextInt();
if (numWeight == (int)numWeight) {
    ((Salad)menu[itemNum - 1]).setWeight(numWeight);

    System.out.println(menu[itemNum - 1].showOrderDetails());
    System.out.println("-------------------------------------------");
    System.out.println("Total No. of items ordered :");

    orderedItem[TtlOrderNum] = menu[itemNum - 1];
    TtlOrderNum += 1;

    Continue();
}
else {
    System.out.println("input must a be integer");
}

当我使用这段代码运行它并输入整数时，它显示:

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at SaladAndDrinkOrderSystem.placeOrder(SaladAndDrinkOrderSystem.java:69)
    at TestSaladAndDrinkOrderSystem.main(TestSaladAndDrinkOrderSystem.java:23)

Answer 1

你需要做类似的事情:

int numweight;
try {
    numweight = sc.nextInt();
    // Rest of your code here...
} catch (InputMismatchException e) {
    System.err.println("Please enter an integer");
}

为了不让java抛出输入不匹配的异常。