能给解释一下每一块具体是干嘛的吗实在是不理解

Question

package dao;

import java.awt.Container;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.TableColumn;




public class ClassManager extends JFrame{
    Container c = getContentPane();

    private Statement stm;
    private ResultSet rs;
    private JTable table;
    private JScrollPane js;
    private JTextField text1,text2,text3;
    private JPanel jp;
    private int count,id;
    private JLabel change1,change2,change3,change4;
    private Connections connections;
    public ClassManager(){
        super();
        //标题
        setTitle("班级管理");
        //设置布局
        setLayout(null);
        //不可放大缩小
        setResizable(false);
        //设置窗口大小
        setBounds(570,260,680,520);
        //可关闭
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        //调用方法
        search();
        data();
        //可视化
        setVisible(true);
        
        
    }
    public void search(){
    
            jp = new JPanel();
            jp.setLayout(null);
            jp.setBounds(0,0,680,520);
            //组件
            JLabel jl = new JLabel("班级管理");
            
    
            //设置字体
            Font font = new Font("宋体",Font.BOLD,24);
            jl.setFont(font);
            
            jl.setBounds(270, 10, 200, 40);
            JLabel jl1 =  new JLabel("请输入班级编号:");
            jl1.setBounds(150,50,150,30);
            text1 = new JTextField("",13);
            text1.setBounds(250,50,100,25);
            c.add(jl1);
            c.add(text1);        
            //按钮监听
            JButton btn1 = new JButton("查询");
            btn1.setBounds(380,49,60,25);
            btn1.addActionListener(new ActionListener(){        
                @Override
                public void actionPerformed(ActionEvent e) {                
                    find();                    
                }
            });    
            c.add(btn1);
            
            
            JButton btn2 = new JButton("更新");
            btn2.setBounds(530,49,60,25);
            btn2.addActionListener(new ActionListener(){        
                @Override
                public void actionPerformed(ActionEvent e) {    
                    //调用方法
                    update();                    
                }
            });    
            JButton btn3 = new JButton("删除");
            btn3.setBounds(600,49,60,25);
            btn3.addActionListener(new ActionListener(){        
                @Override
                public void actionPerformed(ActionEvent e) {                
                    delete();                    
                }
            });    
            JButton btn4 = new JButton("添加");
            btn4.setBounds(460,49,60,25);
            btn4.addActionListener(new ActionListener(){        
                @Override
                public void actionPerformed(ActionEvent e) {                
                    add();                    
                }
            });    
            ///表格头
            String[] columnName=
                {"班号","名字"};
            String[][] tableValues =new String[20][columnName.length];
            table = new JTable(tableValues,columnName);                                
            table.setBounds(30,100,620,320);
            table.getTableHeader().setReorderingAllowed(false);
            Enumeration<TableColumn> cms = table.getColumnModel().getColumns();
            while(cms.hasMoreElements()){
                cms.nextElement().setPreferredWidth(200);
            }
            //表格加入滚动条
            js = new JScrollPane(table);
            js.setBounds(30,90,610,320);
            jp.add(js);    
            
            //面板添加组件        
        jp.add(btn2);
        jp.add(btn4);
        jp.add(btn3);
        jp.add(jl);
        c.add(jp);        
    }

    public void data(){
        
        try {
            //获取数据连接
            connections = new Connections();
            Connection con =  connections.getConnection();
            stm = (Statement) con.createStatement();
            Statement stm1 = (Statement) con.createStatement();
            //获取数据库数据
            rs = stm.executeQuery("select *  from classes");            
            ResultSet rs1 = stm1.executeQuery("select count(*) from classes");
            while(rs1.next()){
                count = rs1.getInt(1);
            }
            //把数据放进集合
            ArrayList save = new ArrayList();
            while(rs.next()){
                String Str1 = rs.getString(1);
                String Str2 = rs.getString(2);
        
                
                
                save.add(Str1);
                save.add(Str2);
        
    
                
            }
                //取出数据
                Iterator iterator = save.iterator();//迭代器遍历里面元素
                while(iterator.hasNext()){
                    //把数据设置进表格
                for(int i =0;i<count;i++){
                    for(int j = 0;j<2;j++){    
                        String data = (String) iterator.next();
                        table.setValueAt(data, i, j);
                    }    
            }
            }
            
        } catch (Exception e1) {
            e1.printStackTrace();
        }                    
    }
    public void find(){
            //把表格所有数据清空
            try {
                for(int i =0;i<count+2;i++){
                    for(int j = 0;j<2;j++){    
                        
                        table.setValueAt("", i, j);
                    }    
            }
                connections = new Connections();
                Connection con =  connections.getConnection();
                stm = (Statement) con.createStatement();
                Statement stm1 = (Statement) con.createStatement();
                //获取输入的数据
                String t1 = text1.getText();
                rs = stm.executeQuery("select *  from classes where  id='"+t1+"'");            
                ResultSet rs1 = stm1.executeQuery("select count(*) from classes where id='"+t1+"'");
                while(rs1.next()){
                    count = rs1.getInt(1);
                }
                //把数据放进集合
                ArrayList save = new ArrayList();
                while(rs.next()){
                    String Str1 = rs.getString(1);
                    String Str2 = rs.getString(2);


                    
                    
                    save.add(Str1);
                    save.add(Str2);
            
                    
        
                    
                }
                    //取出数据
                    Iterator iterator = save.iterator();//迭代器遍历里面元素
                    while(iterator.hasNext()){
                        //把数据设置进表格
                    for(int i =0;i<count;i++){
                        for(int j = 0;j<2;j++){    
                            String data = (String) iterator.next();
                            
                            table.setValueAt(data, i, j);
                        }    
                }
                }
                
            } catch (Exception e1) {
                e1.printStackTrace();
            }                    
        }
    
    public void add(){
        try {
            //获取数据库连接
            connections = new Connections();
            Connection con =  connections.getConnection();
            
            stm = (Statement) con.createStatement();
            
            //获取表格选择行
            int index = table.getSelectedRow();
            //获取选择行数据
            String ISBN = (String) table.getValueAt(index, 0);
            String name = (String) table.getValueAt(index, 1);

    
    
    
            //添加进数据库
            String sql = ("insert into classes values('"+ISBN+"','"+name+"')");
            
            int resule2 = stm.executeUpdate(sql);
            if(resule2==1){
                //添加成功则弹出弹窗
                JOptionPane.showMessageDialog(null,"添加成功","确认",JOptionPane.PLAIN_MESSAGE);
            }
            stm.close();
            con.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            JOptionPane.showMessageDialog(null,"编号相同","确认",JOptionPane.PLAIN_MESSAGE);
        }
        
    }
    public void update(){
        try {
            //连接数据库
            connections = new Connections();
            Connection con =  connections.getConnection();
            
            stm = (Statement) con.createStatement();
            
            int index = table.getSelectedRow();
            //获取表格数据
            String ISBN = (String) table.getValueAt(index, 0);
            String name = (String) table.getValueAt(index, 1);

            

            //执行数据库语句
            String sql = ("update classes set name='"+name+"' where id='"+ISBN+"'");
            
            int resule2 = stm.executeUpdate(sql);
            if(resule2==1){
                //数据库成功修改数据后弹出对话框
                JOptionPane.showMessageDialog(null,"更新成功","确认",JOptionPane.PLAIN_MESSAGE);
                
            }
            stm.close();
            con.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 
        
    }
    
    public void delete(){
        try {
            //获取数据库数据
            connections = new Connections();
            Connection con =  connections.getConnection();
            
            stm = (Statement) con.createStatement();
            //获取表格数据
            int index = table.getSelectedRow();
            String ISBN = (String) table.getValueAt(index, 0);
            //删除数据库语句
            String sql = ("delete from classes where id='"+ISBN+"'");
            
            int resule2 = stm.executeUpdate(sql);
            if(resule2==1){
                //删除成功弹出对话框
                JOptionPane.showMessageDialog(null,"删除成功","确认",JOptionPane.PLAIN_MESSAGE);
                
            }
            stm.close();
            con.close();
            
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            //表格数据全部清空
            for(int i =0;i<count+2;i++){
                for(int j = 0;j<2;j++){    
                    
                    table.setValueAt("", i, j);
                }    
        }
            //表格重新刷新数据
            data();
        }
    }
    
    public static void main(String[] args){
        ClassManager user = new ClassManager();
    }

    
    

}

Answer 1

• ClassManager() 构造函数的作用是初始化该类时，同时利用JPanel相关组件生成一个可视窗口用于数据操作；

• data 方法是填充数据，相当于页面默认加载需要的数据。需要去数据库查询列表然后回显至刚才生成的那个窗口

• search 方法动态渲染了搜索需要的相关页面元素，必须搜索按钮或搜索框；

• 其他比如 add 对应增加数据、update 对应修改数据、find 对应搜索数据、delete 对应删除数据；
  码字不易，还望收纳！