JAVA+Swing +sql 分页代码

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.AbstractTableModel;
public class PageTest extends JFrame implements MouseListener,ActionListener{
 public final  String[] columnHeaders = {"ID(编号)","Nmae(姓名)","Sex(性别)" };
 JTable ab;
 JLabel ab1,ab2,ab3,ab4;
 JTextField test1,test2,test3,test01,test02,test03,test04;
 JButton bu,bu1,bu01,bu02,bu03,bu04;
 JScrollPane jsp;
 public String[][] str = null;
 ShuZhu sz = new ShuZhu();
 int y =0;
 public PageTest(){
  sz.sqlCont();
  setTitle("------------------");
  setBounds(100,100,500,400);
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  setLayout(null);
  bu  = new JButton("下一页");
  bu.setBounds(415,10,75,30);
  bu.addActionListener(this);
  bu1  = new JButton("上一页");
  bu1.setBounds(415,50,75,30);
  bu1.addActionListener(this);
  ShuZhu sz = new ShuZhu();
  str = sz.selectSql(3,y);
  testChn tc = new testChn();
  
  ab = new JTable(tc);
  jsp = new JScrollPane(ab);
  jsp.setBounds(10,10,400, 80);
  ab.addMouseListener(this);
  test1 = new JTextField(20);
  test1.setBounds(20,100,100,35);
  test2 = new JTextField(20);
  test2.setBounds(170,100,100,35);
  test3 = new JTextField(20);
 &nbs