Question

 if (input.equals("arbitrary"))
    {
        System.out.println("What is your mass?");
        massPerson = Double.parseDouble(input);
        System.out.println("What is the planet's weight?");
        massPlanet = Double.parseDouble(input);
        System.out.println("What is the radius of the planet?");
        radiusPlanet = Double.parseDouble(input);
        weight = arbitraryPlanetWeight(massPerson, massPlanet, radiusPlanet);
    }

我试图运行一个程序，让它在不同的星球上重量。除了我任意的行星，一切都在起作用。如果您在"arbitrary"中输入void main(string[]args)，则会询问"What is your weight"并停止运行参数。它说我有NumberFormatException。我该如何解决这个问题？

Answer 1

我已经写了一个我假设你要做的事情的例子。阅读所有评论，他们应该帮助您理解代码。

public static void main(String[] args) {

    /*args is a array of String so for example:
    ["arbitrary"] -> array of length == 1
    or
    ["12.2","11.1","13.3"]
    */

    //If there were no elements in the array this code would break but we will assume there is at least one
    String input = args[0];//put the first element in the array into input

    double weight,massPerson,massPlanet,radiusPlanet;//define variables that we will use

    if (input.equals("arbitrary"))//we look is the string equal to "arbitrary"
    {
        System.out.println("What is your mass?");
        //The next commented out line if it where a command could not pass here because you are trying to interpret "arbitrary" as a double value
        //double massPerson = Double.parseDouble(input);
        //instead you want to user to input the value
        Scanner s = new Scanner(System.in);
        input = s.nextLine(); //now input is what the user has entered
        //we assume that what the user has entered is a number
        //if the user input something like "hello" the code would break and you would again get the NumberFormatException
        massPerson = Double.parseDouble(input);
        System.out.println("What is the planet's weight?");
        input = s.nextLine();
        massPlanet = Double.parseDouble(input);
        System.out.println("What is the radius of the planet?");
        input = s.nextLine();
        radiusPlanet = Double.parseDouble(input);
        s.close();//it is important to close the scanner -> there is also a try syntax to do this closing automatically so google : " try-with-resources Statement"
    }
    else{//we have something else as the input
        //lets assume then that the args[] has 3 values which can all be parsed 
        //also since we have the values there is no need to ask the user 
        massPerson = Double.parseDouble(args[0]);//take the first value in the args array and pars it
        massPlanet = Double.parseDouble(args[1]);//take the second value in the args array and pars it
        radiusPlanet = Double.parseDouble(args[2]);//take the third value in the args array and pars it
    }
    //we have all the values at this point so we can calculate the weight
    weight = arbitraryPlanetWeight(massPerson, massPlanet, radiusPlanet);

}

private static double arbitraryPlanetWeight(double massPerson, double massPlanet, double radiusPlanet) {
    System.out.println("Do some calculations");
    return 50;//dummy result
}

Answer 2

如果你的String输入等于任意，它不能表示数字，那么Double.parseDouble（输入）会启动一个解析异常。

您应该为每个所需信息设置变量：

    if (input.equals("arbitrary"))
    {
        System.out.println("What is your mass?");
        massPerson = Double.parseDouble(massPersonStr);
        System.out.println("What is the planet's weight?");
        massPlanet = Double.parseDouble(massPlanetStr);
        System.out.println("What is the radius of the planet?");
        radiusPlanet = Double.parseDouble(radiusPlanetStr);
        weight = arbitraryPlanetWeight(massPerson, massPlanet, radiusPlanet);
    }

数字格式例外？

2 个答案: