if语句循环答案

【问题标题】：If statement loopif语句循环
【发布时间】：2020-08-21 21:23:27
【问题描述】：

所以我制作了一个程序来根据用户的需求来解决不同的数学问题，并且我不希望程序在用户完成后结束。现在，我刚才的循环一遍又一遍地重复相同的选项。想要的效果是能够继续选择你想做的问题。我对编码还很陌生，所以如果这是一个简单的问题，我深表歉意。

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);

【问题讨论】：

标签： java loops if-statement

【解决方案1】：

像这样改变这一点：

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

如果您将keyboard.nextInt() 调用移到do 循环内，它现在会反复询问用户输入。

您在循环之前有这行代码，因此它只处理了一次。

【讨论】：

【解决方案2】：

在循环外声明int response。循环内的地方response = keyboard.nextInt();

在循环之外使用int response = keyboard.nextInt()，您将永远无法再次到达它。另外，将选项放在循环中，以便它们每次都显示。

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);
}

【讨论】：