//引包如下
import java.sql.Connection;
import java.sql.Date;
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 java.util.Scanner;

规范写法：

public static void main(String[] args) {
//      查询XX部门员工的全部信息。
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/mysqldb";
            String username = "root";
            String password = "root";
            con =DriverManager.getConnection(url,username,password);
            
            Scanner sc =new Scanner(System.in);
            System.out.println("请输入部门编号");
            String newdeptno = sc.nextLine();
            
            String sql ="select * from emp where deptno = ?";
            ps = con.prepareStatement(sql);
            ps.setString(1,newdeptno);
            
            rs = ps.executeQuery();
            List<Emp> elist = new ArrayList<Emp>();
            while(rs.next()) {
                int empno = rs.getInt("empno");
                String ename = rs.getString("ename");
                String job = rs.getString("job");
                int mgr = rs.getInt("mgr");
                Date hiredate = rs.getDate("hiredate");
                double sal = rs.getDouble("sal");
                double comm = rs.getDouble("comm");
                int deptno = rs.getInt("deptno");
                System.out.println(deptno);
                Emp e = new Emp();
                e.setEmpno(empno);
                e.setEname(ename);
                e.setJob(job);
                e.setMgr(mgr);
                e.setHiredate(hiredate);
                e.setSal(sal);
                e.setComm(comm);
                e.setDeptno(deptno);
                
                elist.add(e);
                
                for(Emp t:elist) {
                    System.out.println(t.toString());
                }
            }
            
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally {
                try {
                    rs.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }catch(NullPointerException e){
                    e.printStackTrace();
                }finally {
                    try {
                        ps.close();
                    } catch (SQLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }catch(NullPointerException e){
                        e.printStackTrace();
                    }finally {
                        try {
                            con.close();
                        } catch (SQLException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }catch(NullPointerException e){
                            e.printStackTrace();
                        }
                    }
                }
            }
    }