JTable的常见问题

package com.bdc;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;
import javax.swing.table.TableRowSorter;

public class JTableTest extends JFrame {
	String[][] data={{"aaa","111"},{"bbb","222"},{"ccc","333"}};
	String[] cols= {"user","password"};
	DefaultTableModel dtm;
	JTable jtable1;
	public JTableTest() {
		
		//设置基本属性
		setAlwaysOnTop(true);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		setSize(300,300);

		
		//添加组件
		jtable1= new JTable(dtm);
		jtable1.putClientProperty("terminateEditOnFocusLost", true); //失去焦点时退出编辑状态,点击修改按钮时才能获取修改后的值;
		add(jtable1);
		
		JScrollPane jsp= new JScrollPane(jtable1);
		add(jsp);
		
		JPanel jp1=new JPanel();
		add(jp1,BorderLayout.SOUTH);
		
		JButton listAll=new JButton("显示所有");
		jp1.add(listAll);
		
		
		JButton delete=new JButton("删除");
		jp1.add(delete);
		
		JButton modify=new JButton("修改");
		jp1.add(modify);
		
		
		//添加事件监听;
		listAll.addActionListener(new ActionListener() {
			
			@Override
			public void actionPerformed(ActionEvent e) {
				//自定义一个TableModel,重新isCellEditable,设定为第一列不可编辑；
				dtm=new DefaultTableModel(data,cols){
					@Override
					public boolean isCellEditable(int row, int column) {
						return column==1?true:false;
					}
				};
				//创建一个排序器，设为table的排序属性; 点击列名时即可实现排序功能。
				TableRowSorter<TableModel> sorter = new TableRowSorter<TableModel>(dtm);  	
				jtable1.setRowSorter(sorter); 
				jtable1.setModel(dtm);
							
			}
		});
		
		delete.addActionListener(new ActionListener() {
			
			@Override
			public void actionPerformed(ActionEvent e) {
				int a=jtable1.getSelectedRow();
				dtm.removeRow(a); //删除某一行;
			
				jtable1.setModel(dtm);
			}
		});
				
		modify.addActionListener(new ActionListener() {
			
			@Override
			public void actionPerformed(ActionEvent e) {
			
				int aa=jtable1.getSelectedRow();
				int bb=jtable1.getSelectedColumn();
				if (aa==-1) {
					return;
				}
				JOptionPane.showMessageDialog(JTableTest.this, "成功修改为"+jtable1.getValueAt(aa, bb));	
			}
		});
	}

	public static void main(String[] args) {
		new JTableTest().setVisible(true);
		
	}
}