Java SE执行while循环问题

当我编译我的代码时，我的java应用程序有问题，它说找不到符号roomLength 。 应用程序应该做的是提示用户输入房间名称然后如果它“退出”则必须关闭程序。 否则会提示房间的长度，宽度和高度。 如果这些尺寸中的任何一个为零或更小，它将再次重新调整尺寸。

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; } } 

这是我的主要方法。

 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(); if(roomName.equals("quit")) { userInput.close(); } else { 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(); Room r = new Room(roomName, roomLength, roomWidth, roomHeight); } while (roomLength > 0 || roomWidth > 0 || roomHeight > 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()); } } } 

提前致谢！ ;）

还有一个问题几乎与这个问题相似，只是它应该循环回到第一个提示，允许用户输入另一个房间的名称及其尺寸。

Java做的同时循环回到应用程序的开头

干杯!

Answer 1

您正在尝试访问它们声明的范围之外的变量。您必须在do之外声明变量，以便您可以在while访问它们：

  double roomLength; double roomWidth; double roomHeight; do { Scanner dimensionsInput = new Scanner(System.in); System.out.print("Please enter the dimensions of the room, length, width and height accordingly"); roomLength = dimensionsInput.nextDouble(); roomWidth = dimensionsInput.nextDouble(); roomHeight = dimensionsInput.nextDouble(); Room r = new Room(roomName, roomLength, roomWidth, roomHeight); } while (roomLength > 0 || roomWidth > 0 || roomHeight > 0); 

但我现在看到Room的声明范围也是错误的。 如果你想在之后访问它，你必须在循环之前声明它。 所以一个更简单的解决方案可能是：

  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); 

顺便说一句，在所有维度都为0之前你循环似乎是不对的。我怀疑你的意思是检查== 0 。

Answer 2

您必须在do-while循环前面声明变量roomLength ， roomWidth和roomHeight 。

像这样：

 double roomLength = 0; double roomWidth = 0; double roomHeight = 0; do { dimensionsInput = new Scanner(System.in); System.out.print("Please enter the dimensions of the room, length, width and height accordingly"); roomLength = dimensionsInput.nextDouble(); roomWidth = dimensionsInput.nextDouble(); roomHeight = dimensionsInput.nextDouble(); Room r = new Room(roomName, roomLength, roomWidth, roomHeight); } while (roomLength > 0 || roomWidth > 0 || roomHeight > 0); 

问题是变量的范围。 roomLength ， roomWidth和roomHeight只在do roomHeight中可见。 但是while内部的语句不在do -block之内。 这就是为什么无法找到变量的原因。