If语句循环

Question

所以我做了一个程序来做不同的数学题，这取决于用户想要什么，我不希望程序在用户完成之后结束。现在，我的循环重复了一遍又一遍相同的选项。期望的效果是能够不断地选择你想要做的问题。我对编码相当陌生，所以如果这是一个简单的问题，我很抱歉。

public static void main(String[] args)
{
    System.out.println("What problem do you want to do?");
    System.out.println("1:Celcius to Farenheit");
    System.out.println("2:Slope Formula");
    System.out.println("3:Averages");
    System.out.println("4:Perimeter");
    System.out.println("5:Exit\n\n");
    
    Scanner keyboard = new Scanner(System.in);
    
    int response = keyboard.nextInt();

    
    do
    {
    if (response == 1)
    {
        System.out.println("Degrees Celcius:");
        int degrees = keyboard.nextInt();
        System.out.println(degrees + " degrees Celcius is " + celsToFarenheit(degrees) + " degrees Farenheit.");
    }
    else if (response == 2)
    {
        System.out.println("x1:");
        int x1 = keyboard.nextInt();
        System.out.println("y1:");
        int y1 = keyboard.nextInt();
        System.out.println("x2:");
        int x2 = keyboard.nextInt();
        System.out.println("y2:");
        int y2 = keyboard.nextInt();
        System.out.println("The slope is " + slopeFormula(x1,y1,x2,y2));
    }
    else if (response == 3)
    {
        System.out.println("First number:");
        int num1 = keyboard.nextInt();
        System.out.println("Second number:");
        int num2 = keyboard.nextInt();
        System.out.println("The average is " + average(num1,num2));
    }
    else if (response == 4)
    {
        System.out.println("Length:");
        int length = keyboard.nextInt();
        System.out.println("Width:");
        int width = keyboard.nextInt();
        System.out.println("The perimeter is " + perimeter(length,width));
    }
}
while (response != 5);

Answer 1

将此部分更改如下：

do
{
int response = keyboard.nextInt();
if (response == 1)

如果您将keyboard.nextInt()调用移动到do循环中，它现在将反复向用户请求输入。

在循环之前，您有这行代码，所以它只处理了一次。

Answer 2

在循环之外声明int response。在循环内放置response = keyboard.nextInt();

有了循环之外的int response = keyboard.nextInt()，您就再也无法到达它了。另外，将选项放在循环中，这样每次都会显示出来。

public static void main(String[] args) {


    Scanner keyboard = new Scanner(System.in);

    int response;


    do {
        System.out.println("What problem do you want to do?");
        System.out.println("1:Celcius to Farenheit");
        System.out.println("2:Slope Formula");
        System.out.println("3:Averages");
        System.out.println("4:Perimeter");
        System.out.println("5:Exit\n\n");

        response = keyboard.nextInt();
        if (response == 1) {
            System.out.println("Degrees Celcius:");
            int degrees = keyboard.nextInt();
            System.out.println(degrees + " degrees Celcius is " + celsToFarenheit(degrees) + " degrees Farenheit.");
        } else if (response == 2) {
            System.out.println("x1:");
            int x1 = keyboard.nextInt();
            System.out.println("y1:");
            int y1 = keyboard.nextInt();
            System.out.println("x2:");
            int x2 = keyboard.nextInt();
            System.out.println("y2:");
            int y2 = keyboard.nextInt();
            System.out.println("The slope is " + slopeFormula(x1,y1,x2,y2));
        } else if (response == 3) {
            System.out.println("First number:");
            int num1 = keyboard.nextInt();
            System.out.println("Second number:");
            int num2 = keyboard.nextInt();
            System.out.println("The average is " + average(num1,num2));
        } else if (response == 4) {
            System.out.println("Length:");
            int length = keyboard.nextInt();
            System.out.println("Width:");
            int width = keyboard.nextInt();
            System.out.println("The perimeter is " + perimeter(length,width));
        }
    }
    while (response != 5);
}