求助大佬，救救孩子吧！！！

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  本人Java菜鸟，跟着网上做了一个酒店管理系统，用Java Swing做的，添加功能都能正常运行，可是在删除和修改时，出现空指针问题，还有一个查询时，出现sql语句错误，实在想不到招了，求区里大佬求助

一下是问题：

 

 

 以下是代码：

删除：

package view;

import java.awt.EventQueue;

import javax.swing.JInternalFrame;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;

import dao.HotelTypeDao;
import model.HotelType;
import util.DbUtill;
import util.StringUtill;

import javax.swing.JLabel;
import javax.swing.JOptionPane;

import java.awt.Font;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.LayoutStyle.ComponentPlacement;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.awt.event.ActionEvent;

public class HotelDel extends JInternalFrame {
	private JTextField delNotxt;
	
	private DbUtill dbUtill = new DbUtill();
	private HotelTypeDao hotelTypeDao;


	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					HotelDel frame = new HotelDel();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public HotelDel() {
		setTitle("删除");
		setIconifiable(true);
		setClosable(true);
		setBounds(100, 100, 613, 421);
		
		JLabel lblNewLabel = new JLabel("删除的房间号");
		lblNewLabel.setFont(new Font("Dialog", Font.BOLD, 25));
		
		delNotxt = new JTextField();
		delNotxt.setColumns(10);
		
		JButton btnNewButton = new JButton("确认删除");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				hotelDelActionPerformed(e);
			}
		});
		btnNewButton.setFont(new Font("宋体", Font.BOLD, 22));
		GroupLayout groupLayout = new GroupLayout(getContentPane());
		groupLayout.setHorizontalGroup(
			groupLayout.createParallelGroup(Alignment.LEADING)
				.addGroup(groupLayout.createSequentialGroup()
					.addGroup(groupLayout.createParallelGroup(Alignment.LEADING)
						.addGroup(groupLayout.createSequentialGroup()
							.addGap(82)
							.addComponent(lblNewLabel, GroupLayout.PREFERRED_SIZE, 174, GroupLayout.PREFERRED_SIZE)
							.addGap(44)
							.addComponent(delNotxt, GroupLayout.PREFERRED_SIZE, 197, GroupLayout.PREFERRED_SIZE))
						.addGroup(groupLayout.createSequentialGroup()
							.addGap(215)
							.addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 146, GroupLayout.PREFERRED_SIZE)))
					.addContainerGap(106, Short.MAX_VALUE))
		);
		groupLayout.setVerticalGroup(
			groupLayout.createParallelGroup(Alignment.LEADING)
				.addGroup(groupLayout.createSequentialGroup()
					.addGap(131)
					.addGroup(groupLayout.createParallelGroup(Alignment.LEADING)
						.addComponent(delNotxt, GroupLayout.PREFERRED_SIZE, 33, GroupLayout.PREFERRED_SIZE)
						.addComponent(lblNewLabel))
					.addPreferredGap(ComponentPlacement.RELATED, 114, Short.MAX_VALUE)
					.addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 49, GroupLayout.PREFERRED_SIZE)
					.addGap(63))
		);
		getContentPane().setLayout(groupLayout);
			
	}
	
	public void resetValue() {
		this.delNotxt.setText("");
	}
	
	private void hotelDelActionPerformed(ActionEvent evt) {
		String delno = delNotxt.getText();
		
		if (StringUtill.isEmpty(delno)) {
			JOptionPane.showMessageDialog(null, "删除号不能为空");
			return;
		}
		
		HotelType hotelType = new HotelType(delno);
		Connection con = null;
		
		try {
			con = dbUtill.getCon();
			int delNum = hotelTypeDao.del(con, hotelType);
			if (delNum==1) {
				JOptionPane.showMessageDialog(null, "删除成功");
				this.resetValue();
			}else {
				JOptionPane.showMessageDialog(null, "删除失败");
			}
		} catch (Exception e) {
			e.printStackTrace();
			JOptionPane.showMessageDialog(null, "删除失败");
		}finally {
			try {
				dbUtill.closeCon(con);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		
	}
}

修改：

package view;

import java.awt.EventQueue;

import javax.swing.JInternalFrame;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

import java.awt.Font;
import javax.swing.JTextField;
import javax.swing.LayoutStyle.ComponentPlacement;

import dao.HotelTypeDao;
import model.HotelType;
import util.DbUtill;
import util.StringUtill;

import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.awt.event.ActionEvent;

public class HotelAlt extends JInternalFrame {
	private JTextField yudingNoText;
	private JTextField yudingStaText;
	
	private DbUtill dbUtill = new DbUtill();
	private HotelTypeDao hotelTypeDao;

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					HotelAlt frame = new HotelAlt();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public HotelAlt() {
		setTitle("预定");
		setClosable(true);
		setIconifiable(true);
		setBounds(100, 100, 677, 489);
		
		JLabel lblNewLabel = new JLabel("预定房间号");
		lblNewLabel.setFont(new Font("Dialog", Font.BOLD, 19));
		
		JLabel lblNewLabel_1 = new JLabel("修改房间状态");
		lblNewLabel_1.setFont(new Font("宋体", Font.BOLD, 21));
		
		yudingNoText = new JTextField();
		yudingNoText.setColumns(10);
		
		yudingStaText = new JTextField();
		yudingStaText.setColumns(10);
		
		JButton btnNewButton = new JButton("确认");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				hotelAltActionPerformed(e);
			}


		});
		btnNewButton.setFont(new Font("宋体", Font.BOLD, 23));
		GroupLayout groupLayout = new GroupLayout(getContentPane());
		groupLayout.setHorizontalGroup(
			groupLayout.createParallelGroup(Alignment.LEADING)
				.addGroup(groupLayout.createSequentialGroup()
					.addGap(120)
					.addGroup(groupLayout.createParallelGroup(Alignment.LEADING)
						.addComponent(lblNewLabel, GroupLayout.PREFERRED_SIZE, 137, GroupLayout.PREFERRED_SIZE)
						.addComponent(lblNewLabel_1, GroupLayout.PREFERRED_SIZE, 145, GroupLayout.PREFERRED_SIZE))
					.addGap(69)
					.addGroup(groupLayout.createParallelGroup(Alignment.LEADING)
						.addComponent(yudingStaText, GroupLayout.DEFAULT_SIZE, 131, Short.MAX_VALUE)
						.addComponent(yudingNoText, GroupLayout.DEFAULT_SIZE, 131, Short.MAX_VALUE))
					.addGap(202))
				.addGroup(groupLayout.createSequentialGroup()
					.addGap(235)
					.addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 124, GroupLayout.PREFERRED_SIZE)
					.addContainerGap(308, Short.MAX_VALUE))
		);
		groupLayout.setVerticalGroup(
			groupLayout.createParallelGroup(Alignment.LEADING)
				.addGroup(groupLayout.createSequentialGroup()
					.addGap(127)
					.addGroup(groupLayout.createParallelGroup(Alignment.BASELINE)
						.addComponent(lblNewLabel, GroupLayout.PREFERRED_SIZE, 43, GroupLayout.PREFERRED_SIZE)
						.addComponent(yudingNoText, GroupLayout.PREFERRED_SIZE, 29, GroupLayout.PREFERRED_SIZE))
					.addGap(57)
					.addGroup(groupLayout.createParallelGroup(Alignment.TRAILING)
						.addComponent(yudingStaText, GroupLayout.PREFERRED_SIZE, 32, GroupLayout.PREFERRED_SIZE)
						.addComponent(lblNewLabel_1, GroupLayout.PREFERRED_SIZE, 45, GroupLayout.PREFERRED_SIZE))
					.addGap(90)
					.addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 56, GroupLayout.PREFERRED_SIZE)
					.addContainerGap(42, Short.MAX_VALUE))
		);
		getContentPane().setLayout(groupLayout);

	}
	
	//重置表单
		private void reserValue() {
			this.yudingNoText.setText("");
			this.yudingStaText.setText("");
		}
		
		
	private void hotelAltActionPerformed(ActionEvent evt) {
		String yudingNoText = this.yudingNoText.getText();
		String yudingStaText = this.yudingStaText.getText();
		if (StringUtill.isEmpty(yudingNoText)) {
			JOptionPane.showMessageDialog(null, "预定的房间号不能为空");
			return;
		}else if (StringUtill.isEmpty(yudingStaText)) {
			JOptionPane.showMessageDialog(null, "预定的状态不能为空");
			return;
		}
		
		HotelType hotelType = new HotelType(yudingNoText,yudingStaText);
		Connection con = null;
		
		try {
			con = dbUtill.getCon();
			int n = hotelTypeDao.update(con, hotelType);
			if (n==1) {
			JOptionPane.showMessageDialog(null, "酒店预定成功");
			this.reserValue();
			}else {
				JOptionPane.showMessageDialog(null, "酒店预定失败");
			}
		} catch (Exception e) {
			e.printStackTrace();
			JOptionPane.showMessageDialog(null, "酒店预定失败");
		}finally {
			try {
				dbUtill.closeCon(con);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		
	}
}

查找：

package view;

import java.awt.EventQueue;
import java.sql.Connection;
import java.sql.ResultSet;
import java.util.Vector;

import javax.swing.JInternalFrame;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;

import dao.HotelTypeDao;
import model.HotelType;
import util.DbUtill;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class HotelSel extends JInternalFrame {
	private JTable hoteltypetable;
	
	private DbUtill dbUtill = new DbUtill();
	private HotelTypeDao hotelTypeDao = new HotelTypeDao();
	private JTextField statxt;

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					HotelSel frame = new HotelSel();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public HotelSel() {
		setIconifiable(true);
		setClosable(true);
		setBounds(100, 100, 834, 588);
		
		JScrollPane scrollPane = new JScrollPane();
		
		JLabel lblNewLabel = new JLabel("房间状态");
		lblNewLabel.setFont(new Font("宋体", Font.BOLD, 21));
		
		statxt = new JTextField();
		statxt.setColumns(10);
		
		JButton btnNewButton = new JButton("查询");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				HotelTypeSerchActionPerformed(e);
			}

			
		});
		btnNewButton.setFont(new Font("宋体", Font.BOLD, 21));
		GroupLayout groupLayout = new GroupLayout(getContentPane());
		groupLayout.setHorizontalGroup(
			groupLayout.createParallelGroup(Alignment.LEADING)
				.addGroup(groupLayout.createSequentialGroup()
					.addGap(85)
					.addGroup(groupLayout.createParallelGroup(Alignment.LEADING)
						.addGroup(groupLayout.createSequentialGroup()
							.addGap(50)
							.addComponent(lblNewLabel, GroupLayout.PREFERRED_SIZE, 102, GroupLayout.PREFERRED_SIZE)
							.addGap(47)
							.addComponent(statxt, GroupLayout.PREFERRED_SIZE, 208, GroupLayout.PREFERRED_SIZE)
							.addGap(80)
							.addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 107, GroupLayout.PREFERRED_SIZE))
						.addComponent(scrollPane, GroupLayout.PREFERRED_SIZE, 656, GroupLayout.PREFERRED_SIZE))
					.addContainerGap(83, Short.MAX_VALUE))
		);
		groupLayout.setVerticalGroup(
			groupLayout.createParallelGroup(Alignment.LEADING)
				.addGroup(groupLayout.createSequentialGroup()
					.addGap(54)
					.addGroup(groupLayout.createParallelGroup(Alignment.BASELINE)
						.addComponent(statxt, GroupLayout.PREFERRED_SIZE, 32, GroupLayout.PREFERRED_SIZE)
						.addComponent(lblNewLabel, GroupLayout.PREFERRED_SIZE, 39, GroupLayout.PREFERRED_SIZE)
						.addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 43, GroupLayout.PREFERRED_SIZE))
					.addGap(46)
					.addComponent(scrollPane, GroupLayout.PREFERRED_SIZE, 374, GroupLayout.PREFERRED_SIZE)
					.addContainerGap(46, Short.MAX_VALUE))
		);
		
		hoteltypetable = new JTable();
		hoteltypetable.setModel(new DefaultTableModel(
			new Object[][] {
			},
			new String[] {
				"\u623F\u95F4\u53F7", "\u623F\u95F4\u7C7B\u578B", "\u623F\u95F4\u72B6\u6001", "\u623F\u95F4\u4EF7\u683C"
			}
		));
		scrollPane.setViewportView(hoteltypetable);
		getContentPane().setLayout(groupLayout);
		
		this.filltable(new HotelType());

	}
	
	
	//查找所有房间
	private void filltable(HotelType hotelType) {
		DefaultTableModel dtm = (DefaultTableModel)hoteltypetable.getModel();
		dtm.setRowCount(0);
		Connection con = null;
		try {
			con = dbUtill.getCon();
			ResultSet rs = hotelTypeDao.list(con, hotelType);
			while (rs.next()) {
				Vector v = new Vector();
				v.add(rs.getString("h_no"));
				v.add(rs.getString("h_name"));
				v.add(rs.getString("h_sta"));
				v.add(rs.getString("h_price"));
				dtm.addRow(v);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			try {
				dbUtill.closeCon(con);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
	
	//房间状态查询
	private void HotelTypeSerchActionPerformed(ActionEvent evt) {
		String sta = this.statxt.getText();
		HotelType hotelType = new HotelType();
		hotelType.setH_sta(sta);
		this.filltable(hotelType);
	}
}

sql语句：

package dao;


import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import model.HotelType;
import util.StringUtill;

public class HotelTypeDao {
	
	//酒店添加
	public int add(Connection con,HotelType hotelType) throws Exception{
		String sql = "insert into hoteltype values(?,?,?,?);";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1,hotelType.getH_no());
		pstmt.setString(2,hotelType.getH_name());
		pstmt.setString(3,hotelType.getH_sta());
		pstmt.setString(4, hotelType.getH_price());
		return pstmt.executeUpdate();
	}
	
	
	//删除
	public int del(Connection con,HotelType hotelType)  throws Exception{
		String sql = "delete from hoteltype where h_no=?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, hotelType.getH_no());
		return pstmt.executeUpdate();
	}
	
	//修改
	public int update(Connection con,HotelType hotelType) throws Exception {
		String sql = "update hoteltype set h_sta=? where h_no=?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, hotelType.getH_sta());
		pstmt.setString(2, hotelType.getH_no());
		return pstmt.executeUpdate();
	}
	
	public ResultSet list(Connection con,HotelType hotelType) throws Exception {
		StringBuffer sb = new StringBuffer("select * from hoteltype");
		if (StringUtill.isNotEmpty(hotelType.getH_sta())) {
			sb.append(" and h_sta like %"+ hotelType.getH_sta() + "%");
		}
		PreparedStatement pstm = con.prepareStatement(sb.toString().replaceFirst("and", "where"));
		return pstm.executeQuery();
	}
	

}

类

package model;

public class HotelType {
	
	private String h_no;
	private String h_name;
	private String h_sta;
	private String h_price;
	
	
	
	public HotelType() {
		super();
	}
	
	
	public HotelType(String h_no, String h_name, String h_sta, String h_price) {
		super();
		this.h_no = h_no;
		this.h_name = h_name;
		this.h_sta = h_sta;
		this.h_price = h_price;
	}
	
	
	public  HotelType(String yuding_no,String yuding_sta) {
		super();
		this.h_no = yuding_no;
		this.h_sta = yuding_sta;
	}
	
	public  HotelType(String delno) {
		super();
		this.h_no = delno;
	}


	public String getH_no() {
		return h_no;
	}
	public void setH_no(String h_no) {
		this.h_no = h_no;
	}
	public String getH_name() {
		return h_name;
	}
	public void setH_name(String h_name) {
		this.h_name = h_name;
	}
	public String getH_sta() {
		return h_sta;
	}
	public void setH_sta(String h_sta) {
		this.h_sta = h_sta;
	}
	public String getH_price() {
		return h_price;
	}
	public void setH_price(String h_price) {
		this.h_price = h_price;
	}
}

 

...全文
新四化浪潮下，中年整车诊断工程师的黄金突围路 摘要 本文探讨了汽车电子诊断工程师在当前行业变革中的独特优势与发展路径。作者作为从业者指出，整车诊断岗位在汽车"新四化"浪潮中呈现"逆生长"特性：技术壁垒高、经验复利强、市场需求持续增长。中年工程师凭借丰富的案例积累和实战经验成为行业稀缺人才，薪资水平显著高于同龄段其他技术岗位。文章分析了四条职业发展路径（技术专家、技术管理、细分深耕、横向拓展），并警示了三大职业风险（执行层局限、技术停滞、成果沉淀不足）。最后提出具体建议，强调掌握UDS高阶、DoIP以太网诊断等核心技术的重要性，为中年技术人提供了清晰的职 阅读详情

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