消息对话框将不会显示

Question

我认为对话框代码没有问题，我想我的zip变量有问题。最初我把它设置为双倍，并试图使用开关进行附加费计算。我将其更改为字符串，然后切换不起作用，所以我将其更改为if / else语句。编译器没有发现任何错误，但现在输入所有其他数据后，我的最终消息对话框不会显示。我发现其他人询问这个任务，但没有一个人需要使用对话框，这就是我的问题所在。这是我的代码，感谢所有帮助。

import javax.swing.JOptionPane; //Needed for JOptionPane

public class EZShippingCompany
{
  public static void main (String[] args)
 {

  String input;     //to hold the string input
  String zip = new String();  //to hold zip
  double weight;    //to hold weight
  double length;    //to hold length
  double width;     //to hold width
  double height;    //to hold height
  double dimensions;//to hold dimensions

  double shippingcost=0; //to hold shipping cost
  double surcharge=0; //to hold surcharge
  double additionalcharge=0; // to hold additional 2% 
  double totalshippingcost; // to hold total


  //get zip
  input = JOptionPane.showInputDialog ("Please enter your zip code");

  //get weight
  input = JOptionPane.showInputDialog ("Please enter the weight of your shipment");
  weight = Double.parseDouble(input);

  //get length
  input = JOptionPane.showInputDialog ("Please enter the length in inches of your shipment");
  length = Double.parseDouble(input);

  //get width
  input = JOptionPane.showInputDialog ("Please enter the width in inches of your shipment");
  width = Double.parseDouble(input);

  //get height
  input = JOptionPane.showInputDialog ("Please enter the height in inches of your shipment");
  height = Double.parseDouble(input);

  dimensions = length * width * height;

  //calculate shipping cost
  {if (weight <= 5)
     shippingcost = 12.00;

  else if (dimensions + weight >=5.1 && dimensions + weight <= 15)
     shippingcost = 14.00;

  else if (dimensions + weight >= 15 && dimensions + weight <= 34)
     shippingcost = 17.00;

  else if (dimensions + weight >= 34 && dimensions + weight <= 45)
     shippingcost = 21.00;

  else if (dimensions + weight >= 45 && dimensions + weight <= 60)
     shippingcost = 33.00;

  else if (dimensions + weight > 60)
     shippingcost = 105.00;  }


  //calculate surcharge
  int x = zip.charAt(0);

  if (x == 4)
     surcharge = (.05 * shippingcost);
  else if (x == 6)
     surcharge = (.09 * shippingcost);

  else
     surcharge = (.014 * shippingcost);

  totalshippingcost = shippingcost + surcharge + additionalcharge;

  JOptionPane.showMessageDialog(null, "Zip Code: " + zip +
                                      "\nDimensions: " + dimensions + " square inches" +
                                      "\nSurcharge: " + surcharge +
                                      "\nTotal Shipping Cost: $" + totalshippingcost);
  //End the program
  System.exit(0);
  }

}