我有一个基于GUI的电子商店项目。我在一个文件中读取并解析它并将其保存到一个数组中。 文件格式如下： 11111，＆＃34; title＆＃34;，9.90
11111是书名，＆＃34;标题＆＃34;是标题，9.90是价格。
我目前在我的项目中有3个班级。输入/输出1个类，Book store GUI代码1个类，单击特定按钮时弹出框中的另一个类。
在GUI代码中，我检查将文件读入String [] fileArray，然后循环遍历它，直到匹配（使用TextField输入 String bookIds = bookIdinput.getText（））
我能够成功获得匹配并继续使用剩下的代码，但是当没有匹配时，我会收到错误：线程异常＆＃34; JavaFX应用程序线程＆＃ 34; windowDisplay.lambda上的java.lang.NullPointerException $ start $ 3（windowDisplay.java：###）
这段代码for(int i=0; i<fileArray.length; i++)
如果没有匹配，则应显示一个弹出框，说明找不到bookID。
以下是一些GUI代码
public class windowDisplay extends Application
{
// Variable declarations
private String[] fileArray = null;
private String holdStr = "";
private Stage mainWindow;
private boolean matchFound = false;
private int count = 1;
private int lineItems = 1;
private double totalAmount = 0.0;
private double subTotal = 0.0;
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception
{
// OMITTED CODE
// These TextFields show the output depending on the input TextField's.
itemInfoOutput.setDisable(true);
orderSubtotalOutput.setDisable(true);
// Process item button.
processItem.setText("Process Item #" + count);
processItem.setMinWidth(106);
processItem.setOnAction(e ->
{
int numItems = Integer.parseInt(numItemInput.getText());
lineItems = numItems;
String bookIDs = bookIdInput.getText();
int qtyItems = Integer.parseInt(qtyItemInput.getText());
// Read file and check for Book ID
fileArray = bookStoreIO.readFile(bookIDs);
// Loop through array to find match or no matches
for(int i=0; i<fileArray.length; i++)
{
// If there is a match in book ID
if (fileArray[i].equals(bookIDs))
{
double price = Double.parseDouble(fileArray[i + 2]); // Price is in the i+2 position
double discount = calculateDiscount(qtyItems);
totalAmount = calculatePrice(qtyItems, price);
itemInfoOutput.setText(fileArray[i] + " " + fileArray[i + 1] + " " + "$" + price + " " +
qtyItems + " " + discount + "%" + " " + "$" + df.format(totalAmount));
// Disable processItem Button if there is a match and enable confirmItem Button
processItem.setDisable(true);
confirmItem.setDisable(false);
matchFound = true;
}
}
if(matchFound == false)
System.out.println("No match found!");
});
}
// OMITTED CODE
// This method calculates the discount depending on the quantity of items
public static double calculateDiscount(int inputQty){return null;}
// This methdod calculates the price with the discount
public static double calculatePrice(int inputQty, double price){return null;}
}
此类读取文件并返回一个包含该文件内容的数组（一旦被＆＃34;，＆＃34;分隔符拆分）。
public class bookStoreIO
{
// This method reads the input file "inventory.txt" and saves it into an array.
public static String[] readFile(String stringIn)
{
try
{
String nextLine;
String[] fIn;
// Read file
BufferedReader br = new BufferedReader(new FileReader("inventory.txt"));
while((nextLine = br.readLine()) != null)
{
fIn = nextLine.split(", "); // Split when ", " is seen
if(stringIn.equalsIgnoreCase(fIn[0]))
{
br.close(); // Close file
return fIn; // Return array
}
}
}
// Just in case file isn't found
catch(IOException e)
{
System.out.println("File not found.");
}
return null;
}
如果这看起来很混乱我很抱歉，我还是JavaFX和Java编程的新手。 如果您认为需要更多代码，请告诉我们！
编辑：我改进了一些变量命名并删除了for循环。在没有匹配的情况下，我仍然无法检查。
public class windowDisplay extends Application
{
// Variable declarations
private String[] fileArray = null;
private Stage mainWindow;
private boolean matchFound = false;
private int count = 1;
private int lineItems = 1;
private double totalAmount = 0.0;
private double subTotal = 0.0;
private int itemQty = 0;
private int idBook = 0;
private String bookTitle = "";
private double bookPrice = 0.0;
private double discountAmount = 0.0;
private String resultOrder = "";
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception
{
// OMITTED CODE
// These TextFields show the output depending on the input TextField's.
itemInfoOutput.setDisable(true);
orderSubtotalOutput.setDisable(true);
// Process item button.
processItem.setText("Process Item #" + count);
processItem.setMinWidth(106);
processItem.setOnAction(e ->
{
int numItems = Integer.parseInt(numItemInput.getText());
lineItems = numItems;
String bookIDs = bookIdInput.getText();
itemQty = Integer.parseInt(qtyItemInput.getText());
// Read file and check for Book ID
fileArray = bookStoreIO.readFile(bookIDs);
idBook = Integer.parseInt(fileArray[0]);
bookTitle = fileArray[1];
bookPrice = Double.parseDouble(fileArray[2]);
discountAmount = calculateDiscount(itemQty);
totalAmount = calculatePrice(itemQty, bookPrice);
itemInfoOutput.setText(idBook + " " + bookTitle + " $" + bookPrice + " " + itemQty + " " + discountAmount
+ "% $" + df.format(totalAmount));
itemInfo.setText("Item #" + count + " info:");
processItem.setDisable(true);
confirmItem.setDisable(false);
matchFound = true;
if(matchFound == false)
System.out.println("not found");
});
// OMITTED CODE
// This method calculates the discount depending on the quantity of items
public static double calculateDiscount(int inputQty){return null;}
// This method calculates the price with the discount
public static double calculatePrice(int inputQty, double price){return null;}
}
我也遇到了保存问题
itemInfoOutput.setText(idBook + " " + bookTitle + " $" + bookPrice + " " + itemQty + " " + discountAmount
+ "% $" + df.format(totalAmount));
进入一个String或String数组，打印出所有相应匹配的列表（以及他们的书籍ID，书名，书价，数量，折扣和总价）。
示例如下所示： enter image description here
// Process item button.
processItem.setText("Process Item #" + count);
processItem.setMinWidth(106);
processItem.setOnAction(e ->
{
int numItems = Integer.parseInt(numItemInput.getText());
lineItems = numItems;
String bookIDs = bookIdInput.getText();
itemQty = Integer.parseInt(qtyItemInput.getText());
// Read file and check for Book ID
fileArray = bookStoreIO.readFile(bookIDs);
for(int i=0; i<fileArray.length; i++)
System.out.println(fileArray[i]);
if(fileArray.length >= 3)
{
idBook = Integer.parseInt(fileArray[0]);
bookTitle = fileArray[1];
bookPrice = Double.parseDouble(fileArray[2]);
discountAmount = calculateDiscount(itemQty);
totalAmount = calculatePrice(itemQty, bookPrice);
resultOrder = itemInfoOutput.getText();
itemInfoOutput.setText(idBook + " " + bookTitle + " $" + bookPrice + " " + itemQty + " " + discountAmount
+ "% $" + df.format(totalAmount));
resultOrder = idBook + " " + bookTitle + " $" + bookPrice + " " + itemQty + " " + discountAmount
+ "% $" + df.format(totalAmount);
itemInfo.setText("Item #" + count + " info:");
processItem.setDisable(true);
confirmItem.setDisable(false);
}
else
alertBox.confirmDisplay("Book ID " + idBook + " not in file");
});