一、HashSet实现

主函数：

public class TestOne {private static HashSet<Student> set = new HashSet<Student>();public static void main(String[] args) {System.out.println("*********************************");System.out.println("*\t\t\t\t*");System.out.println("*\t欢迎使用学生信息管理系统\t*");System.out.println("*\t\t\t\t*");System.out.println("*********************************");while (true) {menu();}}static void menu() {System.out.println("1、添加学生信息");System.out.println("2、删除学生信息");System.out.println("3、修改学生信息");//地址传递System.out.println("4、查询学生信息");//nameSystem.out.println("请输入操作，以Enter键结束:");Scanner scanner = new Scanner(System.in);int option  = scanner.nextInt();switch (option) {case 1:{Student student = new Student();System.out.println("请输入学生ID");String id = scanner.next();System.out.println("请输入学生姓名");String name = scanner.next();System.out.println("请输入学生电话");String mobile = scanner.next();System.out.println("请输入学生地址");String address = scanner.next();student.setId(id);student.setName(name);student.setMobile(mobile);student.setAddress(address);if(set.contains(student)) {System.out.println("添加失败,学号不允许重复");return;}set.add(student);System.out.println(set.size());System.out.println("添加成功");break;}case 2:{//删除操作System.out.println("请输入要删除学生的id");String id = scanner.next();Student student = new Student();student.setId(id);if(set.remove(student)) {//删除成功返回trueSystem.out.println("删除学生信息成功！！");return;}System.out.println("没有找到该学号的学生信息,删除失败！！！");break;}case 3:{//修改操作System.out.println("请输入要修改学生的学号");String id = scanner.next();Student student = new Student();student.setId(id);if(!set.contains(student)) {System.out.println("没有找到该学号的学生信息!!!");return;}for(Student stu : set) {if(stu.getId().equals(id)) {System.out.println("请输入要修改的学生姓名：");String name = scanner.next();System.out.println("请输入要修改的学生电话：");String mobile = scanner.next();System.out.println("请输入要修改的学生地址");String address = scanner.next();stu.setName(name);stu.setMobile(mobile);stu.setAddress(address);System.out.println("修改学生信息成功");return;}}break;}case 4:{System.out.println("请输入要查询学生的学号：");String id = scanner.next();Student student = new Student();student.setId(id);if(!set.contains(student)) {System.out.println("没有找到该学号的学生信息!!!");return;}for(Student stu : set) {if(stu.getId().equals(id)) {System.out.println(stu);}}break;}default:System.out.println("I'm Sorry,there is not the "+option+" option,please try again.");}}
}

学生类：

public class Student {String id;String name;String mobile;String address;public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getMobile() {return mobile;}public void setMobile(String mobile) {this.mobile = mobile;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}@Overridepublic int hashCode() {return id.hashCode();}@Overridepublic boolean equals(Object obj) {if(obj instanceof Student) {Student stu = (Student)obj;return this.id.equals(stu.id);}return false;}@Overridepublic String toString() {return "Student [id=" + id + ", name=" + name + ", mobile=" + mobile + ", address=" + address + "]";}}

二、数据库实现：

主函数：

public class Main {private static DBLink db = new DBLink();public static void main(String[] args) {System.out.println("*********************************");System.out.println("*\t\t\t\t*");System.out.println("*\t欢迎使用学生信息管理系统\t*");System.out.println("*\t\t\t\t*");System.out.println("*********************************");while (true) {menu();}}static void menu() {System.out.println("1、添加学生信息");System.out.println("2、删除学生信息");System.out.println("3、修改学生信息");//地址传递System.out.println("4、查询学生信息");//nameSystem.out.println("请输入操作，以Enter键结束:");Scanner scanner = new Scanner(System.in);int option  = scanner.nextInt();switch (option) {case 1:{System.out.println("请输入学生id:");String id = scanner.next();String sql = "select id from student where id = '"+id+"'";if(db.exist(sql)) {System.out.println("学号不允许重复！！");return;}System.out.println("请输入学生姓名:");String name = scanner.next();System.out.println("请输入学生电话:");String mobile = scanner.next();System.out.println("请输入学生地址:");String address = scanner.next();String sql1 = "insert into student (id,name,mobile,address) values ('" + id + "','" + name + "','"+ mobile + "','"+address+"')";if(db.update(sql1))System.out.println("学生信息添加成功！！");elseSystem.out.println("添加失败!!!");break;}case 2:{System.out.println("请输入要删除学生的学号：");String id = scanner.next();String sql = "select id,name,mobile,address from student where id = '"+id+"'";if(db.exist(sql)) {String sql1 = "delete from student where id = '" + id + "'";if(db.update(sql1))System.out.println("删除学生信息成功!!");elseSystem.out.println("删除失败！！");}else {System.out.println("没有该学号的学生信息!!");}break;}case 3:{System.out.println("请输入要修改学生的学号：");String id = scanner.next();String sql1 = "select id from student where id = '" + id+ "'";if(!db.exist(sql1)) {System.out.println("没有该学号的学生信息！！");return;}System.out.println("请输入修改的学生姓名:");String name = scanner.next();System.out.println("请输入修改的学生电话:");String mobile = scanner.next();System.out.println("请输入修改的学生地址:");String address = scanner.next();String sql = "update student set name = '"+name+"',mobile = '"+mobile+"',address = '"+address+"'where id = '"+id+"'";if(db.update(sql)) {System.out.println("修改成功！！");}else {System.out.println("修改失败!!");}break;}case 4:{System.out.println("请输入待查询学生的id：");String id = scanner.next();String sql = "select id,name,mobile,address from student where id = '"+id+"'";if(!db.exist(sql)) {System.out.println("没有该学生信息!!");return;}IRowMapper rowmapper = new IRowMapper() {@Overridepublic void rowMapper(ResultSet rs) {try {while(rs.next()) {String id = rs.getString("id");String name = rs.getString("name");String mobile = rs.getString("mobile");String address = rs.getString("address");System.out.println(id+","+name+","+mobile+","+address);}} catch (SQLException e) {e.printStackTrace();}}};db.select(sql, rowmapper);break;}default:System.out.println("I'm Sorry,there is not the "+option+" option,please try again.");}}
}

数据库连接自定义类：

public class DBLink {private Connection getConnection() {try {Class.forName("com.mysql.jdbc.Driver");String url = "jdbc:mysql://127.0.0.1:3306/test";return DriverManager.getConnection(url, "root", "root");} catch (Exception e) {e.printStackTrace();}return null;}public boolean update(String sql) {Connection connection = null;Statement statement = null;try {connection = getConnection();statement = connection.createStatement();int result = statement.executeUpdate(sql);return result>0;} catch (Exception e) {e.printStackTrace();}finally {close(statement,connection);}return false;}public void select(String sql,IRowMapper rowMapper) {//接口无法创建对象，所以rowMapper参数一定指向IRowMapper接口实现类对象Connection connection = null;Statement statement = null;ResultSet resultset = null;try {connection = getConnection();statement = connection.createStatement();//*********执行语句*********resultset = statement.executeQuery(sql);rowMapper.rowMapper(resultset);//因为rowMapper参数指向IRowMapper接口实现类对象，所以此处将调用接口实现类中所实现的rowMapper方法  多态} catch (Exception e) {e.printStackTrace();}finally {close(resultset,statement,connection);}}public boolean exist(String sql) {Connection connection = null;Statement statement = null;ResultSet resultset = null;try {connection = getConnection();statement = connection.createStatement();//*********执行语句*********resultset = statement.executeQuery(sql);return resultset.next();} catch (Exception e) {e.printStackTrace();}finally {close(resultset,statement,connection);}return false;}//方法的重载private void close(ResultSet resultset,Statement statement,Connection connection) {try {if(resultset!= null)resultset.close();} catch (SQLException e) {e.printStackTrace();}close(statement,connection);}private void close(Statement statement,Connection connection) {try {//两个关闭不能在一起捕获，因为上面出异常了，下面资源无法关闭if(statement != null)statement.close();} catch (SQLException e) {e.printStackTrace();}try {if(connection != null)connection.close();} catch (SQLException e) {e.printStackTrace();}}
}

接口：

public interface IRowMapper {void rowMapper(ResultSet rs);
}