问题
In the following method, it doesn't do the addition for the SolarPanel correctly when the input window appears.
When I type in "Electric" followed by "Yes/yes" i get the following Basic Price:20000 Electric Model:2000 Total:22000
but when I do "electric" + "yes/Yes" I get
Basic Price:20000 Electric Model:2000 Solar Panel:5000 Total:27000
how come?
public static int CalculateCost()
{
String typeOfCarCost = askCarType();
String SolarPanelCost = askSolarPanel();
int basicPrice = 20000;
int ElectricModel = 2000;
int SolarPanel = 5000;
int total = 0;
if (typeOfCarCost.equals("Electric") || (typeOfCarCost.equals("electric") && (SolarPanelCost.equals("No") || (SolarPanelCost.equals("no")))))
{
total = basicPrice + ElectricModel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Total:" + total);
}
else if (typeOfCarCost.equals("Electric") || (typeOfCarCost.equals("electric") && (SolarPanelCost.equals("Yes") || (SolarPanelCost.equals("yes")))))
{
total = basicPrice + ElectricModel + SolarPanel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Solar Panel:" + SolarPanel);
System.out.println("Total:" + total);
}
else
{
total += basicPrice;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Total:" + total);
}
return total;
}//ends CalculateCost
For example, it asks: Electric or Hybrid ( I chose Electric, this should add 2000 to the total cost) Electric
Solar Panel (Yes or No, I chose yes. This should add 5000 to the total cost) Yes
The console window displays this however, it doesn't do the addition for the Solar Panel. Basic Price:20000 Electric Model:2000 Total:22000
Additionally, how can I factor in the discount of -500 on the total when both an Electric Model and Solar Panel are chosen.
The whole code is posted below. Any advice?
import javax.swing.*;
public class short7 {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
PrintOptions();
}//ends main
public static String askCarType()
{
String typeOfCar;
typeOfCar = JOptionPane.showInputDialog("Electric or Hybrid?");
if (!typeOfCar.equals("Electric") && (!typeOfCar.equals("electric") && (!typeOfCar.equals("Hybrid") && (!typeOfCar.equals("hybrid")))))
{
JOptionPane.showMessageDialog(null, "You have to choose either an Electric or Hybrid type of car.");
typeOfCar = JOptionPane.showInputDialog("Electric or Hybrid?");
}
return typeOfCar;
}//ends askCarType
public static String askSolarPanel()
{
String wantSolarPanel;
wantSolarPanel = JOptionPane.showInputDialog("Do you want a Solar Panel?");
if (!wantSolarPanel.equals("Yes") && (!wantSolarPanel.equals("yes") && (!wantSolarPanel.equals("No") && (!wantSolarPanel.equals("no")))))
{
JOptionPane.showMessageDialog(null, "You have to enter either Yes or No");
wantSolarPanel = JOptionPane.showInputDialog("Do you want a Solar Panel?");
}
return wantSolarPanel;
}//ends askSolarPanel
public static int calculateDiscount()
{
String typeOfCarSelected = askCarType();
String SolarPanelSelected = askSolarPanel();
int Discount = 0;
if (typeOfCarSelected.equals("Electric") && (typeOfCarSelected.equals("electric") && (typeOfCarSelected.equals("Hybrid") && (typeOfCarSelected.equals("hybrid") & SolarPanelSelected.equals("Yes") || SolarPanelSelected.equals("yes")))))
{
Discount = 500;
}
else
{
Discount = 0;
}
return Discount;
}//ends calculateDiscount
public static int CalculateCost()
{
String typeOfCarCost = askCarType();
String SolarPanelCost = askSolarPanel();
int basicPrice = 20000;
int ElectricModel = 2000;
int SolarPanel = 5000;
int total = 0;
if (typeOfCarCost.equals("Electric") || (typeOfCarCost.equals("electric") & (SolarPanelCost.equals("No") || (SolarPanelCost.equals("no")))))
{
total = basicPrice + ElectricModel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Total:" + total);
}
else if (typeOfCarCost.equals("Electric") || (typeOfCarCost.equals("electric") & (SolarPanelCost.equals("Yes") || (SolarPanelCost.equals("yes")))))
{
total = basicPrice + ElectricModel + SolarPanel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Solar Panel:" + SolarPanel);
System.out.println("Total:" + total);
}
else
{
total += basicPrice;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Total:" + total);
}
return total;
}//ends CalculateCost
public static void PrintOptions()
{
int printTotal = CalculateCost();
}//ends PrintOptions
}//ends class short7
回答1:
You need to use double bracket and '&&' as below:-
if ((typeOfCarCost.equals("Electric") || typeOfCarCost.equals("electric")) && ((SolarPanelCost.equals("No") || SolarPanelCost.equals("no")))
{
total = basicPrice + ElectricModel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Total:" + total);
}
else if ((typeOfCarCost.equals("Electric") || typeOfCarCost.equals("electric")) && (SolarPanelCost.equals("Yes") || SolarPanelCost.equals("yes")))
{
total = basicPrice + ElectricModel + SolarPanel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Solar Panel:" + SolarPanel);
System.out.println("Total:" + total);
}
回答2:
I think instead of single & you need to have double && in your if statement.
Change this:
if (typeOfCarCost.equals("Electric") || (typeOfCarCost.equals("electric") & (SolarPanelCost.equals("No") || (SolarPanelCost.equals("no")))))
to this:
if (typeOfCarCost.equals("Electric") || (typeOfCarCost.equals("electric") &&(SolarPanelCost.equals("No") || (SolarPanelCost.equals("no")))))
Similarly in rest of your if statements. Change that!
On a side note:
As RhinoFeeder commented below its important that you understand the difference between & and &&. So the difference is simple:
&& is logical AND. It evaluates the left side of the operation, if it's true, it continues and evaluates the right side.
& is bitwise AND. It evaluates both sides of the operation.
EDIT:-
Even after your edit you missed the & here
& SolarPanelSelected.equals("Yes")
Try to change your if else block like this:
if ((typeOfCarCost.equals("Electric") || typeOfCarCost.equals("electric")) && ((SolarPanelCost.equals("No") || SolarPanelCost.equals("no")))
{
total = basicPrice + ElectricModel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Total:" + total);
}
else if ((typeOfCarCost.equals("Electric") || typeOfCarCost.equals("electric")) && (SolarPanelCost.equals("Yes") || SolarPanelCost.equals("yes")))
{
total = basicPrice + ElectricModel + SolarPanel;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Electric Model:" + ElectricModel);
System.out.println("Solar Panel:" + SolarPanel);
System.out.println("Total:" + total);
}
else
{
total += basicPrice;
System.out.println("Basic Price:" + basicPrice);
System.out.println("Total:" + total);
}
回答3:
You use & in a couple of places when you should use &&. Then, it always computes both sides. This might not matter, but it's bad form.
Second, you have control of what askCarType will return. Don't use Strings. Create an enum:
enum CarType {
ELECTRIC, HYBRID //Include GASOLINE, DIESEL if you want.
}
This way, you can just use == instead of equals. Even if you are forced to use Strings, document which strings you are returning from askCarType, and only return one of Electric and electric. Any time you are checking for equality with one of two capitalized forms of a string you control, you are making a mistake. Do something similar with askSolarPanel, though you might want to use a boolean instead.
When you do complex boolean expressions, use parentheses. Use them a lot for clarity.
Solar panels on cars? Why?
来源：https://stackoverflow.com/questions/20291656/if-statement-operator-being-ignored