我在Java AddressBook上遇到问题，我试图编辑和更新存储在.csv文件中的一行数据中的值
我尝试遍历代码并检查逻辑错误，但似乎找不到引发try catch异常的原因。确实确实可以做到这一点，却无法弄清停止运行的原因
private class ammendActionListener implements ActionListener {
public ammendActionListener() {
}
@Override
public void actionPerformed(ActionEvent arg0) {
String filePath = "Personal.csv";
String editTerm = id.getText();
String newID = id.getText();
String newFName = fn.getText();
String newLName = ln.getText();
String newAddr = addr.getText();
String newAddr2 = addr2.getText();
String newPost = post.getText();
String newCont = cont.getText();
editRecord(filePath, editTerm, newID, newFName, newLName, newAddr, newAddr2, newPost, newCont);
}
}
private Scanner x;
public void editRecord(String filePath, String editTerm, String newID, String newFName, String newLName, String newAddr, String newAddr2, String newPost, String newCont){
String tempFile = "temp.csv";
File oldFile = new File(filePath);
File newFile = new File(tempFile);
String ID = ""; String first = ""; String last = ""; String addr =""; String addr2=""; String post = ""; String cont = "";
try{
FileWriter fw = new FileWriter(tempFile, true);
BufferedWriter bw = new BufferedWriter(fw);
PrintWriter pw = new PrintWriter(bw);
x = new Scanner(new File(filePath));
x.useDelimiter("[,\n]");
while(x.hasNext()){
ID = x.next();
first = x.next();
last = x.next();
addr = x.next();
addr2 = x.next();
post = x.next();
cont = x.next();
if(ID.equals(editTerm)){
pw.println(newID+","+newFName+","+newLName+","+newAddr+","+newAddr2+","+newPost+","+newCont);
}else{
pw.println(ID+","+first+","+last+","+addr+","+addr2+","+post+","+cont);
}
}
x.close();
pw.flush();
pw.close();
oldFile.delete();
File dump = new File(filePath);
newFile.renameTo(dump);
}catch(Exception e){
JOptionPane.showMessageDialog(null, "ERROR");
}
}
}
我希望文件通过标识要重写的ID列并重命名temp.csv文件并删除带有更新的行的原始Presonal.csv来修改适当的数据。正确执行
总时间：36.814 s 结束于：2019-07-15T11：07：47 + 01：00
更新错误
java.util.NoSuchElementException
at java.base/java.util.Scanner.throwFor(Scanner.java:937)
at java.base/java.util.Scanner.next(Scanner.java:1478)
at com.mycompany.ppaddressbook.ammContact.editRecord(ammContact.java:174)
at
com.mycompany.ppaddressbook.ammContact$ammendActionListener.actionPerformed(ammContact.java:154)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6632)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6397)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5008)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:389)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:389)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
答案 0 :(得分：0)
我想问题是File#renameTo()。根据Javadoc的说法，此方法在很大程度上依赖于平台库。
此方法的行为的许多方面本质上都依赖于平台：重命名操作可能无法将文件从一个文件系统移动到另一个文件系统，它可能不是原子的，并且如果包含以下内容的文件可能无法成功：目标抽象路径名已存在。应该始终检查返回值，以确保重命名操作成功。
您的代码可在我的环境中使用，但是要使其节省使用在任何平台上，您应该使用NIO-Library（新IO）。这是一个快速代码，可以完成您打算做的事情。请注意，您不需要刷新或关闭读取器/写入器，因为try-with-resources会为您完成这些操作。
public class Test {
public static void main(String[] args) {
Test test = new Test();
test.editRecord("C:/temp/test.csv", "2", "2", "foobar", "baz");
}
public void editRecord(String filePath, String editTerm, String newID, String newFName, String newLName){
String tempFile = "temp.csv";
Path oldPath = Paths.get(filePath);
Path newPath = Paths.get(tempFile);
try(BufferedReader reader = Files.newBufferedReader(oldPath); BufferedWriter writer = Files.newBufferedWriter(newPath)) {
String read;
while( (read = reader.readLine()) != null ) {
String[] line = read.split(",");
if(line[0].equals(editTerm)) {
line[0] = newID;
line[1] = newFName;
line[2] = newLName;
}
writer.append(String.join(",", line));
writer.newLine();
}
} catch (IOException e) {
JOptionPane.showMessageDialog(null, e.getMessage());
}
try {
Files.move(newPath, oldPath, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
JOptionPane.showMessageDialog(null, e.getMessage());
}
}
}
考虑将Files.createTempFile("temp", ".csv");用于临时文件。
由于抛出IOException的可能性很大，因此最好在throws上添加editRecord(...)。您可以捕获异常并将其显示在调用方上。