Question

我无法弄清楚为什么它总是返回arg1的值。我正在建造一个重量转换器。

public double convert(double arg1,int arg2,int arg3) {
    // arg1 = amount, arg2 = from, arg3 = to
    double milligram = 1;
    double gram = 1000;
    double ounce = 28349.5;
    double pound = 453592;
    double answer = 0;
    switch(arg2) {
    case 0: switch(arg3) { // if milligram
            case 0: answer = (arg1 * milligram) / milligram;
            case 1: answer = (arg1 * milligram) / gram;
            case 2: answer = (arg1 * milligram) / ounce;
            case 3: answer = (arg1 * milligram) / pound;
    }
    case 1: switch(arg3) { // if gram
            case 0: answer = (arg1 * gram) / milligram;
            case 1: answer = (arg1 * gram) / gram;
            case 2: answer = (arg1 * gram) / ounce;
            case 3: answer = (arg1 * gram) / pound;
    }
    case 2: switch(arg3) { // if ounce
            case 0: answer = (arg1 * ounce) / milligram;
            case 1: answer = (arg1 * ounce) / gram;
            case 2: answer = (arg1 * ounce) / ounce;
            case 3: answer = (arg1 * ounce) / pound;
    }
    case 3: switch(arg3) { // if pound
            case 0: answer = (arg1 * pound) / milligram;
            case 1: answer = (arg1 * pound) / gram;
            case 2: answer = (arg1 * pound) / ounce;
            case 3: answer = (arg1 * pound) / pound;
    }
    } // end arg2 switch
    return answer;
}

我在逻辑中的某个地方搞砸了，但我没能看到哪里。任何帮助将不胜感激。

Answer 1

您缺少break语句：

case 0: 
   answer = (arg1 * milligram) / milligram;
   break;
   ...

Answer 2

重写像这样的每个案例

case 2: switch(arg3) { // if ounce
        case 0: answer = (arg1 * ounce) / milligram;break;
        case 1: answer = (arg1 * ounce) / gram;break;
        case 2: answer = (arg1 * ounce) / ounce;break;
        case 3: answer = (arg1 * ounce) / pound;break;

Answer 3

嵌套的case语句非常难以阅读，而且难以调试。最好将所需的功能封装到方法调用中。

话虽如此，交换机中的任何地方都没有break语句。无论如何，它都将落到最后一个案例（设置答案等于案件的底部）。

Answer 4

您应该在switch语句中使用break，否则您的结果可能会被取消

Answer 5

除了使用break之外，使用return语句可以解决这个问题，同时还可以防止案件崩溃。

case 2: switch(arg3) { // if ounce
    case 0: return (arg1 * milligram) / milligram;

在Java中使用switch的问题

5 个答案: