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我正在尝试编写一个自定义异常，该异常在使用 GUI 和 jtextfield 输入数据时找到空字段。这是我第一次真正处理异常并写一个，所以我不确定该怎么做。下面的代码是我到目前为止能够弄清楚的，它不起作用。我的问题是，是否有人有任何指示或进展可以为我指明正确的方向来完成这项工作。

import javax.swing.*;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedList;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class PersonFrame extends JFrame {

/**
 * 
 */
private static final long serialVersionUID = 1L;
static LinkedList<Person> listOfObjects = new LinkedList<Person>(); 
JTextField fName;
JTextField lName;
JTextField Height;


public PersonFrame()
{
    setTitle("Person");
    setSize(200, 130);
    setLocationRelativeTo(null);
    setLayout(new GridLayout(4,2));
    add(new JLabel("First Name"));
    fName = new JTextField();
    add(fName);
    add(new JLabel("Last Name"));
    lName = new JTextField();
    add(lName);
    add(new JLabel("Height"));
    Height = new JTextField();
    add(Height);
    JButton jbtSubmit = new JButton("Submit");
    JButton jbtCancel = new JButton("Cancel");
    add(jbtSubmit);
    add(jbtCancel);
    SubmitListenerClass listener1 = new SubmitListenerClass();
    CancelListenerClass listener2 = new CancelListenerClass();
    jbtSubmit.addActionListener(listener1);
    jbtCancel.addActionListener(listener2);
    setVisible(true);

}

public void CloseWindow()
{
    this.setVisible(false);
}
public Person SubmitData()
{
    String fn = fName.getText();
    String ln = lName.getText();
    String h = Height.getText();
    int h1 = 0; 
    if(!(h.equals(""))){
    h1 = Integer.parseInt(Height.getText());    
    }   
    Person p = new Person(fn, ln, h1);
    int i = OneMissingFieldException(p);
    if(i == 1);
    System.out.println(p);

    return p;
    }


public void OutputList() throws IOException
{
    if(listOfObjects.peekFirst()!=null)
    {
        PrintWriter pw = new PrintWriter( new FileWriter("outputp.txt") );
        Object[] pa = listOfObjects.toArray();
        pw.println("Person");
        for(int x = 0; x<pa.length; x++)
        {
            pw.println(pa[x]);
            pw.println("");
        }
        pw.close();
    }
 }

class CancelListenerClass implements ActionListener {
  public void actionPerformed(ActionEvent e) {
    CloseWindow();
  }
}
 class SubmitListenerClass implements ActionListener {
  public void actionPerformed(ActionEvent e) {


      listOfObjects.add(SubmitData());
    CloseWindow();

}
}

public int OneMissingFieldException(Person p) extends Exception
{
    System.out.println("one");
    String fName = ((Person) p).getFName();
    String lName = ((Person) p).getFName(); 
    int height = ((Person) p).getHeight();  
    try 
    {
        System.out.println("two");
    if(fName == "" || fName == null || fName == " ");
        throw new MissingFieldException();

    }
    catch(MissingFieldException mfe){
        System.out.println("You did not enter a first name.");
        return 0;
    }

    try 
    {
    if(lName == "" || lName == null || lName == " ")

        throw new MissingFieldException();          
    }
    catch(MissingFieldException mfe){
        System.out.println("You did not enter a last name." + mfe);
        return 0;
    }

    try 
    {

    if(height ==  0 )

        throw new MissingFieldException();
    }
    catch(MissingFieldException mfe){
        System.out.println("You did not enter a height." + mfe);
    return 0;
    }

return 1;

}

经过一段时间的工作后，这就是我所拥有的。只是想知道我是否朝着正确的方向前进。

public Person SubmitData()
{
    Person p = null;
    try{
    String fn = fName.getText();
    String ln = lName.getText();
    String h = Height.getText();
    int h1 = 0; 
    if(!(h.equals(""))){
    h1 = Integer.parseInt(Height.getText());    
    p = new Person(fn, ln, h1);
    checkForMissingFields(p);
    }   

    }
    catch(MissingFieldException e){
    }


    System.out.println(p);

    return p;
    }

  public class MissingFieldException extends Exception {

/**
 * 
 */
private static final long serialVersionUID = 1L;

/**
 * @param args
 */
public static void main(String args){}
public MissingFieldException() { } 
public MissingFieldException( String msg ) {
      super( msg );
 }
public void checkForMissingFields( Object o ) throws MissingFieldException {
int i =OneMissingFieldException(o);
if(i == 1)
    throw new MissingFieldException();

 }


public static int OneMissingFieldException(Object o)
{
    if (o instanceof Person)
{
        String fName = ((Person) o).getFName();
        String lName = ((Person) o).getFName(); 
        int height = ((Person) o).getHeight();


        if(fName == "" || fName == null || fName == " "){
            System.out.println("You did not enter a first name.");  
            return 1;
        }


        if(lName == "" || lName == null || lName == " "){
            System.out.println("You did not enter a last name.");
            return 1;
        }

        if(height == 0)     {       
            System.out.println("You did not enter a height.");
            return 1;           
        }
        return 0;
}
        }
}
4

1 回答 1

0

您在下面的行中将方法和类混为一谈。

public int OneMissingFieldException(Person p) extends Exception
{ ... }

您需要两种不同的构造。

这是一个基本的自定义异常类：

public static class MissingFieldException extends Exception {
     public MissingFieldException() { } 
     public MissingFieldException( String msg ) {
          super( msg );
     }
}

这是一个可以抛出异常的方法：

 public void checkForMissingFields( Person p ) throws MissingFieldException {
      ...
 }

您可以在不检查返回值的情况下调用此方法。这就是例外情况。您可以使用 catch 块检测何时引发异常。

public Person submitData() {
    Person p = null;
    try {
       p = ...;
       checkForMissingFields( p );
       ...
    }
    catch ( MissingFieldException e) {
       // handle exception
    }
    return p;
}
于 2013-04-07T18:22:20.867 回答