身体质量指数计算器（BMI）

package com.bmi.dao; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import com.bmi.bean.BmiBean; public class DBHelper { public static final String url="jdbc:mysql://127.0.0.1:3306/db_bmi"+"?useUnicode=true&characterEncodeing=utf8"; public static final String user="root"; public static final String password="wjljyx"; public static final String name="com.mysql.jdbc.Driver"; private Connection connection; public PreparedStatement prepareStatement; private static ResultSet set; public DBHelper(String sql) { //ctrl+1 快捷键 try { Class.forName(name); System.out.println("驱动加载成功！"); connection = DriverManager.getConnection(url, user, password); System.out.println("驱动链接成功！"); prepareStatement = connection.prepareStatement(sql); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.println("驱动加载失败！"); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.println("驱动链接失败！"); } } /*存储数据到数据库*/ public static boolean addBmi(BmiBean bean) { String sql="insert tb_bmiInfo(date,height,weight,bmi) values(?,?,?,?)"; DBHelper db= new DBHelper(sql); try { db.prepareStatement.setString(1, bean.getDate()); db.prepareStatement.setString(2, bean.getHeight()); db.prepareStatement.setString(3, bean.getWeight()); db.prepareStatement.setString(4, bean.getBmi()); int update=db.prepareStatement.executeUpdate(); if (update>0) { return true; } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ db.close(); } return false; } /* * */ public static List<BmiBean> getBmi() { String sql="select * from tb_bmiInfo"; DBHelper db=new DBHelper(sql); List<BmiBean> list=null; try { set = db.prepareStatement.executeQuery(); list= new ArrayList<>(); while(set.next()){ BmiBean bean=new BmiBean(); bean.setBmi(set.getString("bmi")); bean.setDate(set.getString("date")); bean.setHeight(set.getString("height")); bean.setWeight(set.getString("weight")); bean.setId(set.getInt("id")); list.add(bean); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ db.close(); } return list; } public static boolean delete_Bmi(String flag) { int id=Integer.valueOf(flag); String sql="delete from tb_bmiInfo where id=?"; DBHelper db= new DBHelper(sql); System.out.println(sql); try { db.prepareStatement.setInt(1, id); int update=db.prepareStatement.executeUpdate(); if (update>0) { return true; } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return false; } public void close(){ if(connection!=null){ try{ connection.close(); prepareStatement.close(); }catch(SQLException e){ e.printStackTrace(); }finally{ connection=null; prepareStatement=null; } } } }