Question

好吧，伙计们，我迷失在这一点上。这是我的代码：

public static void main(String[] args)
{
    Scanner input = new Scanner(System.in);
    double weight;
    double newWeight;
    int planet;

    System.out.println("1. Mercury");
    System.out.println("2. Venus");
    System.out.println("3. Earth");
    System.out.println("4. Mars");
    System.out.println("5. Jupiter");
    System.out.println("6. Saturn");
    System.out.println("7. Uranus");
    System.out.println("8. Neptune");
    System.out.println("9. Pluto");
    System.out.println("                   ");
    System.out.println("Select a planet from above: ");
    planet = input.nextInt();
    System.out.println("Enter your weight in pounds: ");
    weight = input.nextInt();

    switch(newWeight) {
        case 1: (3.724 / 9.8) * weight = newWeight; break;
        case 2: (8.918 / 9.8) * weight = newWeight; break;
        case 3: (9.8 / 9.8) * weight = newWeight; break;
        case 4: (3.724 / 9.8) * weight = newWeight; break;
        case 5: (24.892 / 9.8) * weight = newWeight; break;
        case 6: (10.584 / 9.8) * weight = newWeight; break; 
        case 7: (8.918 / 9.8) * weight = newWeight; break;
        case 8: (11.662 / 9.8) * weight = newWeight; break;
        case 9: (1.622 / 9.8) * weight = newWeight; break;
    }
    System.out.print("Your weight on " + planet + "is: " + newWeight);
}

编辑*****：确定没错，重量是一个int而newWeight是一个双倍。但现在是最后一行"System.out.print("your weight on " + planet + "is: " + newWeight);

它说"variable newWeight might not have been initialized".如果不是一件事，那就是另一件事。

Answer 1

赋值运算符的左侧应该是左值，而不是表达式，更改

     (1.622 / 9.8) * weight = newWeight

到

        newWeight = (1.622 / 9.8) * weight

Answer 2

在我看来，您的weight和newWeight变量已被换掉。

首先，您尝试启用尚未设置值的newWeight，然后您正在执行(3.724 / 9.8) * weight = newWeight，这根本没有意义。

我想您想要启用planet，然后使用

设置newWeight

newWeight = (3.724 / 9.8) * weight;

至于最后一行代码的错误，它正在发生，因为如果没有输入数字1到9，则newWeight为null。您可以添加默认大小写，也可以将所有变量初始化为0，如下所示：

int planet = 0;
double weight = 0.00, newWeight = 0.00;

Answer 3

这里的错误比其他答案提到的更多：

您已将weight声明为double，但您要为其指定代码input.nextInt()。应该是input.nextDouble()？
作为其他答案：您的switch应该在planet上，即switch(planet)
作为其他答案，您的newWeight作业已回到正面，例如newweight = (3.724 / 9.8) * weight
您尚未捕获用户为星球输入任何其他号码的情况。
您需要一个默认大小写，以确保已正确设置所有所需的变量。您的编辑可能会警告您这种可能性，default: newweight = 0

Answer 4

好的，你们摇滚！让一切正常，除了地球的名称不会通过。相反，它显示了与该数字对应的行星的数字选择。但我会弄明白的。非常感谢你们的帮助！如果有人想知道他们在另一个星球上的重量是什么，这里是完成的代码：

public static void main(String[] args)
{
    Scanner input = new Scanner(System.in);
    double weight;
    double newWeight;
    int planet;

    System.out.println("1. Mercury");
    System.out.println("2. Venus");
    System.out.println("3. Earth");
    System.out.println("4. Mars");
    System.out.println("5. Jupiter");
    System.out.println("6. Saturn");
    System.out.println("7. Uranus");
    System.out.println("8. Neptune");
    System.out.println("9. Pluto");
    System.out.println("                   ");
    System.out.println("Select a planet from above: ");
    planet = input.nextInt();
    System.out.println("Enter your weight in pounds: ");
    weight = input.nextDouble();

    switch(planet) {
        default: newWeight = 0.00;
        case 1: newWeight = (3.724 / 9.8) * weight; break;
        case 2: newWeight = (8.918 / 9.8) * weight; break;
        case 3: newWeight = (9.8 / 9.8) * weight; break;
        case 4: newWeight = (3.724 / 9.8) * weight; break;
        case 5: newWeight = (24.892 / 9.8) * weight; break;
        case 6: newWeight = (10.584 / 9.8) * weight; break; 
        case 7: newWeight = (8.918 / 9.8) * weight; break;
        case 8: newWeight = (11.662 / 9.8) * weight; break;
        case 9: newWeight = (1.622 / 9.8) * weight; break;
    }
    System.out.print("On " + planet + ", your new weight is: " + newWeight);
}

}

Answer 5

首先，你应该将newWeight初始化为0.

double newWeight = 0;

和上面所说的一样，它应该是个案（星球）。

switch(planet) {
        case 1: newWeight = (3.724 / 9.8) * weight; break;
        case 2:  newWeight = (8.918 / 9.8) * weight; break;
        case 3:  newWeight = (9.8 / 9.8) * weight; break;
        case 4:  newWeight = (3.724 / 9.8) * weight; break;
        case 5:  newWeight = (24.892 / 9.8) * weight; break;
        case 6:  newWeight = (10.584 / 9.8) * weight; break; 
        case 7:  newWeight = (8.918 / 9.8) * weight; break;
        case 8:  newWeight = (11.662 / 9.8) * weight; break;
        case 9:  newWeight = (1.622 / 9.8) * weight; break;
}

也可以在最终的印刷语句中使用行星的名称而不是数字。也许把行星的所有名字都放到一个数组中。这是为了让你开始：）

    ArrayList<String> planetName = new ArrayList(){{
        add("Mercury");
        add("Venus");
        add("Earth");
        add("Mars");
        add("Jupiter");
        add("Saturn");
        add("Uranus");
        add("Neptune");
        add("Pluto");
    }
    };

    for(int i = 0; i < planetName.size(); i++){
        System.out.println((i+1) + ". "+ planetName.get(i)  );
    }

Answer 6

不应该是switch(planet)吗？否则你需要打开任意重量。

Answer 7

您在switch语句中放置了不正确的变量，而您的作业operators则相反。

switch(planet) {
    case 1: newWeight = (3.724 / 9.8) * weight; break;
    //....
}

必需：可变;找到：交换机中的值

7 个答案: