一个月来单个程序最长的，大神来赐教 - 黑马程序员技术交流社区

import java.io.FileWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;
public class Test {
public static void main(String[] args) throws Exception {
Scanner sc=new Scanner(System.in);
Scanner sc2=new Scanner(System.in);
//arrayList存储三个学生的信息
ArrayList<Person> list=new ArrayList<>();
for(int i=0;i<4;i++){
System.out.println("请输入学生的姓名:");
String name=sc.nextLine();
System.out.println("请输入学生的年龄:");
int age=sc2.nextInt();
System.out.println("请输入学生的性别:");
String sex=sc.nextLine();
System.out.println("请输入学生的专业:");
String study=sc.nextLine();
list.add(new Person(name,age,sex,study));
}
// //循环遍历
for (Person p : list) {
System.out.println(p);
}
for (int i = 0; i < list.size(); i++) {
System.out.println(list.get(i));
}
//获得数据库连接
Connection conn=MyJDBCUtils.getConnection();
PreparedStatement ps;
//创建操作数据库的对象
for (Person p : list) {
String sql="insert into Person(pname,psex,page,pstudy) values('"+p.getName()+"','"+p.getSex()+"','"+p.getAge()+"','"+p.getPstudy()+"'); ";
ps = conn.prepareStatement(sql);
ps.executeUpdate(sql);
}
// 查询各个学科的人数
String sql2="select count(*),pstudy from Person group by pstudy ";
ps = conn.prepareStatement(sql2);
ResultSet e= ps.executeQuery(sql2);
while(e.next()){
System.out.print(e.getInt(1)+" ");
System.out.print(e.getString(2)+" ");
System.out.println();
}
//提示用户输入三个id号(已有的) 将年龄改为66
for(int i=0;i<3;i++){
System.out.println("请输入已经存在的pid");
int id=sc.nextInt();
String sql3="update Person set page=66 where pid='"+id+"'";
ps = conn.prepareStatement(sql3);
ps.executeUpdate(sql3);
}
//将姓名作为键值将科目作为值放入map集合中
Map<String,String> map=new HashMap<String, String>();
String sql4="select pname,pstudy from Person ";
ps=conn.prepareStatement(sql4);
ResultSet re = ps.executeQuery(sql4);
while(re.next()){
map.put(re.getString(1), re.getString(2));
}
//遍历双列集合
Set<String> set=map.keySet();
for (String s : set) {
System.out.println(s+"=="+map.get(s));
}
Set<Entry<String,String>> set2= map.entrySet();
for (Entry<String, String> entry : set2) {
System.out.println(entry.getKey()+"==="+entry.getValue());
}
//将表中的数据写入文件中
String sql5="select * from Person ";
ps=conn.prepareStatement(sql5);
ResultSet re1 = ps.executeQuery(sql5);
FileWriter fw=new FileWriter("temp.txt");
while(re1.next()){
fw.write(re1.getString("pid")+" ");
fw.write(re1.getString("pname")+" ");
fw.write(re1.getString("psex")+" ");
fw.write(re1.getInt("page")+" ");
fw.write(re1.getString("pstudy")+" \r\n");
}
fw.close();
conn.close();
ps.close();
}
}

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