Java do while 循环回到应用程序的开头答案

【问题标题】：Java do while loop back to the beginning of applicationJava do while 循环回到应用程序的开头
【发布时间】：2014-06-29 11:18:58
【问题描述】：

此问题是此链接Java SE do while loop issues的后续问题

这是一个询问房间名称的应用程序，然后第二次提示询问其尺寸以执行一些计算。一切都完成后，应用程序应该能够返回到第一个提示询问房间名称等的提示。

class Room
{
private String name;
private double length;
private double width;
private double height;

public Room(String r, double l, double w, double h)
{
    name = r;
    length = l;
    width = w;
    height = h;
}


public String getName()
{
    return name;
}

public double getLength()
{
    return length;
}

public double getWidth()
{
    return width;
}

public double getHeight()
{
    return height;
}

public double getArea()
{
    double area = length*width;
    return area;
}

public double getVolume()
{
    double volume = length*width*height;
    return volume;  
}

public void setName(String s)
{
    name = s;
}
}

还有我运行应用程序的主要方法。

import java.util.Scanner;

class TestRoom
{
public static void main(String [] args)
{
    Scanner userInput = new Scanner(System.in);
    System.out.println("Please enter the name of room");

    String roomName = userInput.next();
    while(!(roomName.equals("quit")))
    {           
        Room r;
        do
        {
            Scanner dimensionsInput = new Scanner(System.in);
            System.out.print("Please enter the dimensions of the room, length, width and height accordingly");

            double roomLength = dimensionsInput.nextDouble();
            double roomWidth = dimensionsInput.nextDouble();
            double roomHeight = dimensionsInput.nextDouble();

            r = new Room(roomName, roomLength, roomWidth, roomHeight);
        }
        while (r.getLength() == 0 || r.getWidth() == 0 || r.getHeight() == 0);


        System.out.println("The name of room: " + r.getName() + " Dimensions: L= " + r.getLength() + 
                                " X " + "W= " + r.getWidth() + " X " + "H= " + r.getHeight());
        System.out.println("Area of room= " + r.getArea());
        System.out.println("Volume of room= " + r.getVolume());

    }
    userInput.close();
}
}

现在应用程序只返回第二个提示而不是第一个提示，所以你们能帮我解决这个问题吗？再次提前感谢各位！

【问题讨论】：

需要在while循环中包含第一个提示不是很明显吗？
房间名称的提示应该在循环内部，而不是外部，因为您希望它重复。
@JBNizet 我已经剪切了提示并将其粘贴到代码 Room r 的正上方；但是虽然编译没问题但是没有运行。
编辑您的问题并在底部发布您的新代码。定义“它不运行”。发生什么了？您意识到您必须继续阅读用户在要求他输入某些内容之后输入的内容，对吧？
编辑您的问题，在原始问题末尾显示您最近的尝试作为附加代码，显示您遇到的错误。也可以使用调试器或使用 println 语句来帮助您调试。

标签： java loops while-loop do-while

【解决方案1】：

您无需声明两个扫描仪。您显然还必须将第一个提示包含在外部 while 循环中。

“固定”代码：

import java.util.Scanner;

class TestRoom
{
    public static void main(String[] args)
    {
        Scanner userInput = new Scanner(System.in);
        String roomName = "";

        while (!(roomName.equals("quit")))
        {
            System.out.println("Please enter the name of room");

            roomName = userInput.next();

            Room r;

            do
            {
                System.out
                        .print("Please enter the dimensions of the room, length, width and height accordingly");

                double roomLength = userInput.nextDouble();
                double roomWidth = userInput.nextDouble();
                double roomHeight = userInput.nextDouble();

                r = new Room(roomName, roomLength, roomWidth, roomHeight);
            } while (r.getLength() == 0 || r.getWidth() == 0
                    || r.getHeight() == 0);

            System.out.println("The name of room: " + r.getName()
                    + " Dimensions: L= " + r.getLength() + " X " + "W= "
                    + r.getWidth() + " X " + "H= " + r.getHeight());
            System.out.println("Area of room= " + r.getArea());
            System.out.println("Volume of room= " + r.getVolume());
        }

        userInput.close();
    }
}

【讨论】：

哇，谢谢，但这行是什么意思？字符串房间名 = "";
表示该String被分配了一个空String。 null 不好，因为在其上调用方法会抛出 NullPointerException。在此示例中，可以分配除 quit 之外的任何字符串，因为它会跳过外部 while 循环。

【解决方案2】：

试试这个：

 class TestRoom {

    static Scanner userInput = new Scanner(System.in);

    static Scanner dimensionsInput = new Scanner(System.in);

    public static void main(String[] args) {

        while(true) {
            prompt();
        }

    }

    private static void prompt() {
        System.out.println("Please enter the name of room");

        String roomName = userInput.next();

        if (roomName.equals("quit")){
            userInput.close();
            dimensionsInput.close();
            System.exit(0);
        }
        Room r;
        do
        {
            System.out
                    .print("Please enter the dimensions of the room, length, width and height accordingly");

            double roomLength = dimensionsInput.nextDouble();
            double roomWidth = dimensionsInput.nextDouble();
            double roomHeight = dimensionsInput.nextDouble();
            r = new Room(roomName, roomLength, roomWidth, roomHeight);
        } while (r.getLength() == 0 || r.getWidth() == 0
                || r.getHeight() == 0);


        System.out.println("The name of room: " + r.getName()
                + " Dimensions: L= " + r.getLength() + " X " + "W= "
                + r.getWidth() + " X " + "H= " + r.getHeight());
        System.out.println("Area of room= " + r.getArea());
        System.out.println("Volume of room= " + r.getVolume());
    }
}

【讨论】：