JDBC增删改查更新版

package com.yxfyg.dao;

public interface UserDao{
    
    void findAll();
    
    void insert(String username,String password,String phone);
    
    void update(int uid,String phone);
    
    void delete(int uid);
}

package com.yxfyg.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import com.yxfyg.dao.UserDao;
import com.yxfyg.util.JDBCUtil;

public class UserDaoImpl implements UserDao{

    @Override
    public void findAll() {
        Connection conn = null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = JDBCUtil.getConn();
            st = conn.createStatement();
            String sql = "select * from user";
            rs = st.executeQuery(sql);
            while(rs.next()) {
                int uid = rs.getInt("uid");
                String username = rs.getString("username");
                String password = rs.getString("password");
                String phone = rs.getString("phone");
                System.out.println("uid="+ uid +",username="+ username +",password="+ password +",phone="+ phone);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.release(rs, st, conn);
        }
    }

    @Override
    public void insert(String username, String password, String phone) {
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            conn = JDBCUtil.getConn();
            String sql = "insert into user values(null,?,?,?)";
            ps = conn.prepareStatement(sql);
            ps.setString(1, username);
            ps.setString(2, password);
            ps.setString(3, phone);
            int row = ps.executeUpdate();
            if(row > 0) {
                System.out.println("插入成功");
            }else {
                System.out.println("插入失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.release(ps,conn);
        }
    }

    @Override
    public void update(int uid, String phone) {
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            conn = JDBCUtil.getConn();
            String sql = "update user set phone = ? where uid = ?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, phone);
            ps.setInt(2, uid);
            int row = ps.executeUpdate();
            if(row > 0) {
                System.out.println("修改成功");
            }else {
                System.out.println("修改失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.release(ps,conn);
        }
    }

    @Override
    public void delete(int uid) {
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            conn = JDBCUtil.getConn();
            String sql = "delete from user where uid = ?";
            ps = conn.prepareStatement(sql);
            ps.setInt(1, uid);
            int row = ps.executeUpdate();
            if(row > 0) {
                System.out.println("删除成功");
            }else {
                System.out.println("删除失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.release(ps,conn);
        }
    }
}