java - JTable。打印所选行的值，如果所选行为空，则提示错误

我创建了一个包含3列的JTable，并在前2行中插入了一个值。当我选择第一行或第二行并单击“ GetData”按钮时，所选行中的数据将被打印在控制台上，但是！如果我选择其中没有数据的行，则代码dataString = dataObject.toString();的这一行上会出现NullPointerException。

我插入了if else语句来检查dataString或dataObject是否包含null或“”值

import java.awt.FlowLayout;
import java.util.Scanner;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class JayTable extends JFrame
{
    DefaultTableModel model;
    JTable table;
    String col[] = {"Name","Address","Gender"};

    public static void main(String args[])
    {
        new JayTable().start();
    }

    public void start()
    {
        model = new DefaultTableModel(col,50);
        table=new JTable(model)
        {
            @Override public boolean isCellEditable(int arg0, int arg1)
            {
                return false;
            }
        };
        table.getColumnSelectionAllowed();
        JScrollPane pane = new JScrollPane(table);
        JButton button = new JButton("GetData");
        table.setValueAt("Ritchie Rich",0,0);
        table.setValueAt("The Mansion",0,1);
        table.setValueAt("Male",0,2);
        table.setValueAt("Flintstone", 1, 0);
        table.setValueAt("Rocky Road", 1, 1);
        table.setValueAt("Unknown", 1, 2);

        add(pane);
        add(button);

        button.setEnabled(false);

        ListSelectionModel listSelectionModel = table.getSelectionModel();

        listSelectionModel.addListSelectionListener(new ListSelectionListener()
        {
                public void valueChanged(ListSelectionEvent e)
                {
                    ListSelectionModel lsm = (ListSelectionModel)e.getSource();
                    button.setEnabled(!lsm.isSelectionEmpty());
                }
        });

        button.addActionListener(e ->
        {
            int row = table.getSelectedRow();
            int column;
            Object dataObject = null;
            String dataString = "";

            for(column = 0 ; column < table.getColumnCount(); column++)
            {
                dataObject = table.getValueAt(row, column);
                dataString = dataObject.toString();

                if(dataObject == null || dataObject.equals("") || dataString ==null || dataString.equals("") )
                    System.out.println("No value");
                else
                    System.out.print(dataString+", ");
            }
            System.out.println();
        });

        setSize(500,400);
        setLayout(new FlowLayout());
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        pack();
        setVisible(true);
    }
}

最佳答案

您的空支票为时已晚。更改为

dataObject = table.getValueAt(row, column);
if(dataObject == null || "".equals(dataObject)) {
     System.out.println("No value");
} else {
      dataString = dataObject.toString();
      if(dataString ==null || "".equals(dataString) )
          System.out.println("No value");
       else
         System.out.print(dataString+", ");
}