public int RetBooks(Borrow r) { int ret = 0; try{ borCon.connectDB(); String sqlret = "update borrow set state='"+"0"+"' where ISBN='" + r.getIsbn() + "' and readerID=" + r.getID(); borCon.statement = borCon.connection.prepareStatement(sqlret); ret = borCon.statement.executeUpdate(sqlret); } catch (SQLException throwable) { throwable.printStackTrace(); }finally { borCon.close(); } return ret; }

public List<BForm> selectByISBNAndReaderId(String ISBN,String ReaderId) { System.out.println("select_BookName_And_ReaderId..."); bList=new ArrayList(); try { Bfcon.connectDB(); String sql="SELECT bor.borrowDate,bor.staffID,b.ISBN, b.bookname,b.likeCount,bor.borrowCount,bor.state FROM books b INNER JOIN Borrow bor ON b.ISBN = bor.ISBN WHERE bor.readerID = '"+ReaderId+"' AND b.ISBN LIKE ?"; Bfcon.statement=Bfcon.connection.prepareStatement(sql); Bfcon.statement.setString(1, "%"+ISBN+"%"); Bfcon.resultSet=Bfcon.statement.executeQuery(); while(Bfcon.resultSet.next()){ bf =new BForm(); bf.setB_isbn(Bfcon.resultSet.getString("ISBN")); bf.setB_name(Bfcon.resultSet.getString("bookname")); bf.setJy_id(Bfcon.resultSet.getString("staffID")); bf.setJy_date(Bfcon.resultSet.getString("borrowDate")); bf.setJy_count(Bfcon.resultSet.getInt("borrowCount")); System.out.println(Bfcon.resultSet.getString("state")); if(Bfcon.resultSet.getInt("state")==0){ bf.setIs_gh("是"); }else if(Bfcon.resultSet.getInt("state")==1){ bf.setIs_gh("否"); } bList.add(bf); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ Bfcon.close(); } //创建一条通路 return bList; }

其中，通过使用连接查询将books表和Borrow表进行关联，根据读者ID和书籍ISBN进行筛选。最终将查询到的信息封装到BForm对象中，并将其添加到List集合中返回。值得注意的是，该代码存在SQL注入漏洞，应该使用...

update book left join (select bno, count(*) as borrow_num from borrow where rdate is null group by bno) as borrow_count on book.bno = borrow_count.bno set book.available = coalesce(book.number, 0) - coalesce(borrow_count.borrow_num, 0);将该sql语句规范化

SET book.available = COALESCE(book.number, 0) - COALESCE(borrow_count.borrow_num, 0); 规范化步骤： 1. 将 SQL 关键字大写（如 UPDATE、LEFT JOIN、SET、FROM、WHERE、GROUP BY、COUNT、COALESCE 等）。 ...

讲以下代码转换为c语言形式：#include <iostream> #include <string> #include <algorithm> using namespace std; // 实现大数加法 string add(string x, string y) { string res; int carry = 0, i = x.size() - 1, j = y.size() - 1; while (i >= 0 || j >= 0 || carry) { int sum = carry; if (i >= 0) sum += x[i--] - '0'; if (j >= 0) sum += y[j--] - '0'; carry = sum / 10; res += to_string(sum % 10); } reverse(res.begin(), res.end()); return res; } // 实现大数减法 string subtract(string x, string y) { string res; int borrow = 0, i = x.size() - 1, j = y.size() - 1; while (i >= 0 || j >= 0) { int diff = borrow; if (i >= 0) diff += x[i--] - '0'; if (j >= 0) diff -= y[j--] - '0'; if (diff < 0) { diff += 10; borrow = -1; } else { borrow = 0; } res += to_string(diff); } reverse(res.begin(), res.end()); return res; } int main() { string a, b; cout << "请输入两个无符号大数，以空格分隔：" << endl; cin >> a >> b; string sum = add(a, b); string difference = subtract(a, b); cout << "它们的和为：" << sum << endl; cout << "它们的差为：" << difference << endl; return 0; }

int borrow = 0, i = strlen(x) - 1, j = strlen(y) - 1, k = 0; while (i >= 0 || j >= 0) { int diff = borrow; if (i >= 0) diff += x[i--] - '0'; if (j >= 0) diff -= y[j--] - '0'; if (diff < 0) { ...

btn_jie.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { // TODO Auto-generated method stub int bian=Integer.valueOf(txt_bian.getText()); String shuming=txt_buildingNo.getText(); LocalDateTime borrowtime=LocalDateTime.now(); int userid=Denglu.user.getId(); String sql="insert into borrowdetail(user_id,room_id,room_status,borrow_time) values('"+userid+"','"+bian+"',1,'"+borrowtime+"')"; try { Connection conn=DbUtil.getConnection(); Statement stm=conn.createStatement(); int n=DataB.data_update(sql, stm); if(n>0) { JOptionPane.showMessageDialog(null, "教室借阅成功"); }else { JOptionPane.showMessageDialog(null, "教室借阅失败"); } }catch(Exception ex) { ex.printStackTrace(); } } });

7. 如果"n"大于0，则弹出一个提示框，提示用户借阅成功；否则，弹出一个提示框，提示用户借阅失败。 8. 如果执行过程中发生异常，则打印异常信息。代码涉及到数据库连接和操作，其中的一些方法和变量没有提供代码...

public class BorrowTableHelper { //新增借阅信息 public boolean AddBorrow(DBHelper dbHelper, Borrow borrow){ SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("botime",borrow.getBotime()); values.put("bookid",borrow.getBookid()); values.put("userid",borrow.getUserid()); values.put("bostate",borrow.getBostate()); long id = db.insert("borrow",null,values); db.close(); boolean flag; if (id != -1){ flag = true; }else { flag = false; } return flag; } //查询借阅记录 public ArrayList<Borrow> ShowBorrow(DBHelper dbHelper,String uid){ SQLiteDatabase db = dbHelper.getWritableDatabase(); Cursor cursor = db.rawQuery("select * from borrow where userid = ? order by boid desc",new String[]{uid}); ArrayList<Borrow> list = new ArrayList<>(); if (cursor != null && cursor.getCount() > 0){ while (cursor.moveToNext()){ String bookid = cursor.getString(cursor.getColumnIndex("bookid")); String botime = cursor.getString(cursor.getColumnIndex("botime")); int bostate = cursor.getInt(cursor.getColumnIndex("bostate")); String backtime = cursor.getString(cursor.getColumnIndex("backtime")); String reviewer = cursor.getString(cursor.getColumnIndex("reviewer")); Borrow borrow = new Borrow(botime,bookid,bostate,backtime,reviewer); list.add(borrow); } } db.close(); return list; }解释每一行代码

10. public ArrayList<Borrow> ShowBorrow(DBHelper dbHelper,String uid){ 这是ShowBorrow方法的开始，它有两个参数，一个是DBHelper类型的dbHelper，表示用于操作数据库的帮助类；另一个是String类型的uid，...

#include <iostream> #include <cstring> using namespace std; #define MAX_LENGTH 100 // 高精度加法 string add(string num1, string num2) { string res = ""; // 存放结果 int carry = 0; // 存放进位 int len1 = num1.size(); int len2 = num2.size(); // 从低位到高位逐位相加 for (int i = len1 - 1, j = len2 - 1; i >= 0 || j >= 0; i--, j--) { int a = i >= 0 ? num1[i] - '0' : 0; int b = j >= 0 ? num2[j] - '0' : 0; int sum = a + b + carry; carry = sum / 10; res = to_string(sum % 10) + res; } while (res.size()>1 && res[0]=='0') { res.erase(0,1); } if (carry > 0) { res = to_string(carry) + res; } return res; } // 高精度减法 string sub(string num1, string num2) { string res = ""; // 存放结果 int borrow = 0; // 存放借位 int len1 = num1.size(); int len2 = num2.size(); // 从低位到高位逐位相减 for (int i = len1 - 1, j = len2 - 1; i >= 0 || j >= 0; i--, j--) { int a = i >= 0 ? num1[i] - '0' : 0; int b = j >= 0 ? num2[j] - '0' : 0; int diff = a - b - borrow; if (diff < 0) { diff += 10; borrow = 1; } else borrow = 0; res = to_string(diff) + res; } // 去掉前导0 while (res.size()>1 && res[0]=='0') { res.erase(0,1); } // 如果结果为0，则去掉负号 if (res == "0") { borrow = 0; } // 加上负号 if (borrow > 0) { res = "-" + res; } return res; } int main() { string num1, num2, op; cin >> num1 >> op >> num2; if (op == "+") { cout << add(num1, num2) << endl; } else if (op == "-") { cout << sub(num1, num2) << endl; } return 0; }这段程序没有考虑被减数小于减数的情况，请改正他使其能够正确返回被减数小于减数时的结果

int borrow = 0; int len1 = num1.size(); int len2 = num2.size(); bool negative = false; // 是否为负数 if (len1 ) { // 如果被减数长度小于减数长度，则交换两个数的位置 swap(num1, num2); len1 = ...

DELIMITER ;;CREATE DEFINER=~root~@localhost” PROCEDUREextend time'(in book num in int out result varchar(5)) begin declare latetime smallint; declare result varchar(5) default 成功';declare borrow rec num in int; set borrow rec num in = (select borrow rec_num from borrows where borrow state = 还' and book num = book num in); select datediff(CURDATE() , borrow time) borrow duration into latetime from borrows where borrow rec num = borrow rec num in;if latetime > @ then set result = 超期';else update borrows set borrow duration = borrow duration + 15where borrow rec num = borrow rec num in; end if; select result; end ;;

具体来说，这段代码会接受一个书籍编号(book num in)，然后会在借阅记录表(borrows)中查找该书籍的借阅记录，并且该记录的状态为“已还”(borrow state = '还')。如果找到符合条件的记录，那么会计算出该记录的借阅...

#include <iostream> #include <cstring> using namespace std; #define MAX_LENGTH 100 // 字符串逆序 void reverse(string& s) { int left = 0, right = s.length() - 1; while (left < right) { swap(s[left], s[right]); left++, right--; } } // 字符串加法 string add(string num1, string num2) { // 字符串逆序 reverse(num1), reverse(num2); // 用 0 补齐，使它们的长度相等 if (num1.length() < num2.length()) { num1 += string(num2.length() - num1.length(), '0'); } else { num2 += string(num1.length() - num2.length(), '0'); } // 从低位开始，将两个字符串对应位相加，考虑进位，将结果存到一个新的字符串中 string result; int carry = 0; for (int i = 0; i < num1.length(); i++) { int s = num1[i] - '0' + num2[i] - '0' + carry; carry = s / 10; result += to_string(s % 10); } // 如果最高位有进位，则将进位也加上 if (carry > 0) { result += to_string(carry); } // 字符串逆序，删除前导 0，输出结果 reverse(result); result.erase(0, result.find_first_not_of('0')); if (result.empty()) { result = "0"; } return result; } // 字符串减法 string subtract(string num1, string num2) { // 比较被减数和减数的大小 if (num1.length() < num2.length() || (num1.length() == num2.length() && num1 < num2)) { swap(num1, num2); num1 = '-' + num1; } // 字符串逆序 reverse(num1), reverse(num2); // 用 0 补齐，使它们的长度相等 num2 += string(num1.length() - num2.length(), '0'); // 从低位开始，将两个字符串对应位相减，考虑借位，将结果存到一个新的字符串中 string result; int borrow = 0; for (int i = 0; i < num1.length(); i++) { int s = num1[i] - '0' - num2[i] + borrow; if (s < 0) { s += 10; borrow = -1; } else { borrow = 0; } result += to_string(s); } // 字符串逆序，删除前导 0，输出结果 reverse(result); result.erase(0, result.find_first_not_of('0')); if (result.empty()) { result = "0"; } return result; } int main() { string num1, num2, op; cin >> num1 >> op >> num2; if (op == "+") { cout << add(num1, num2) << endl; } else { cout << subtract(num1, num2) << endl; } return 0; }

int borrow = 0; for (int i = 0; i < num1.length(); i++) { int s = num1[i] - '0' - num2[i] + borrow; if (s < 0) { s += 10; borrow = -1; } else { borrow = 0; } result += to_string(s); } ...

public ArrayList<Borrow> AllBorrow(DBHelper dbHelper){ SQLiteDatabase db = dbHelper.getWritableDatabase(); Cursor cursor = db.rawQuery("select * from borrow order by boid desc",null); ArrayList<Borrow> list = new ArrayList<>(); if (cursor != null && cursor.getCount() > 0){ while (cursor.moveToNext()){ String boid = cursor.getString(cursor.getColumnIndex("boid")); String bookid = cursor.getString(cursor.getColumnIndex("bookid")); String botime = cursor.getString(cursor.getColumnIndex("botime")); String userid = cursor.getString(cursor.getColumnIndex("userid")); int bostate = cursor.getInt(cursor.getColumnIndex("bostate")); String backtime = cursor.getString(cursor.getColumnIndex("backtime")); String reviewer = cursor.getString(cursor.getColumnIndex("reviewer")); Borrow borrow = new Borrow(boid,botime,bookid,userid,bostate,backtime,reviewer); list.add(borrow); } } db.close(); return list; } //还书 public void ReturnBook(DBHelper dbHelper,String boid,String backtime,String reviewer){ SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("bostate",1); values.put("backtime",backtime); values.put("reviewer",reviewer); db.update("borrow",values,"boid=?",new String[]{boid}); db.close(); } }解释每一行代码

这段代码是一个 Android 应用程序中的数据库访问类 DBHelper 中的两个方法。...然后，代码通过执行 db.update() 方法，更新 borrow 表中 boid 字段等于传入的 boid 字符串的记录。最后一行关闭数据库连接。

public void putDates() { DefaultTableModel model = (DefaultTableModel) table.getModel(); model.setRowCount(0); Connection con = null; Statement stm=null; try { con = DbUtil.getConnection(); String sql="select * from borrowdetail"; stm=con.createStatement(); ResultSet list = DataB.query(sql, stm); while (list.next()) { Vector rowData = new Vector(); rowData.add(list.getInt("id")); int roomid=list.getInt("room_id"); rowData.add(roomid); int book_status=list.getInt("room_status"); String s_statu=getStu(book_status); rowData.add(s_statu); rowData.add(list.getObject("borrow_time")); rowData.add(list.getDate("return_time")); model.addRow(rowData); } } catch (Exception e) { e.printStackTrace(); }finally{ try { DbUtil.closeCon(con); } catch (Exception e) { e.printStackTrace(); } } } public String getStu(int n) { if(n==1) return "在借"; else return "已还"; }

这段代码是用于在表格中展示借阅详情信息的，其中包含了连接数据库，查询数据等操作。具体来说，这个方法会从数据库中查询所有的借阅信息，并将其展示在一个表格中，其中包括借阅编号、房间编号、借阅状态、借阅时间...

create trigger Book_return_Stock after update on Borrow for each row begin IF NEWselect.ReturnTime IS NOT NULL THEN UPDATE book SET Stock = Stock + 1 where BookID = New.BookID; end if; end; UPDATE Borrow SET ReturnTime = '2023-06-09' WHERE BookID = '1002' AND ReaderID = '20230101';

UPDATE book SET Stock = Stock + 1 WHERE BookID = NEW.BookID; END IF; END; 这个触发器的作用是，当Borrow表的某一行更新后，判断是否已经归还（即ReturnTime是否为NULL），如果已经归还，则将相应图书...

public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) { Borrow borrow = list.get(i); if (borrow != null) { viewHolder.name.setText(String.format("名称：%s",borrow.getMaterial().getName())); User user = null; // 在此处添加从服务器或本地数据库中获取User对象的代码，例如： user = UserDB.getUserById(borrow.getUserId()); viewHolder.user.setText(String.format("借用人：%s",user.getName())); //viewHolder.user.setText(String.format("借用人：%s",borrow.getUserId())); viewHolder.borrowQuantity.setText(String.format("借用数量：%s",borrow.getBorrowQuantity())); viewHolder.status.setText(String.format("借用状态：%s", BorrowStatusEnum.getName(borrow.getStatus()))); viewHolder.time.setText(String.format("借用时间：%s",borrow.getTime())); viewHolder.itemView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (mItemListener!=null){ mItemListener.ItemClick(borrow); } } }); viewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener() { @Override public boolean onLongClick(View view) { mItemListener.Delete(borrow); return false; } }); } }安卓程序修改成这样子为什么会报错？

2. 在 onBindViewHolder() 方法中的某个地方出现了 NullPointerException，即 borrow 或 borrow.getMaterial() 或 borrow.getUserId() 为空。 3. BorrowStatusEnum.getName() 方法未定义或未导入。 4. ...

修改代码public class CLI { private static Scanner input = new Scanner(System.in); public static void main(String[] args){ Library library = new Library("UIC Library"); String names; int number ; int borrow; int totalBorrowedBooks = 50; // initial value int action = 0; Scanner scanner = new Scanner(System.in); while (action != 6) { System.out.print("Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): "); String input = scanner.nextLine(); try { action = Integer.parseInt(input); } catch (NumberFormatException e) { System.out.println("You must type an integer!"); continue; } Object bookCounts; switch (action) { case 4: System.out.println("Enter the name of the user: "); names = scanner.next(); System.out.println("Enter the number of books: "); number = scanner.nextInt(); if(!names.equals("Anna") && !names.equals("Bob")) { System.out.println("User "+ names +" unknown."); break;//add break to end this operation. } System.out.println("Type an action (total:1 add:2 get:3 more:4 less:5 quit:6):"); borrow = scanner.nextInt(); System.out.print("Enter the name of the user:"); names = scanner.next(); if (names.equals("Anna")) { number -= borrow; if (number < -5) { System.out.println("You can't borrow more books. Return some books first."); } else { System.out.println(names+" borrows " + (-5 + number -1) + "book(s)."); } }else if(names.equals("Bob")) { number -= borrow; if (number > 10) { System.out.println("You can't borrow more books. You have reached the maximum limit."); } else if(number>0||number<10){ System.out.println(names+" borrows " + (10 - number +1) + " book(s)."); } else if(number<0){ System.out.println("Positive integers only!"); System.out.println("Enter the number of books:"); number = scanner.nextInt(); System.out.println(names+" borrows " + (10 - number +1) + " book(s)."); // Directly output the result after modification. } }else { System.out.println("User "+ names +" unknown."); } break;

public class CLI { private static Scanner input = new Scanner(System.in); public static void main(String[] args){ Library library = new Library("UIC Library"); String names; int number; int ...

final SqTipsDialog sqTipsDialog = new SqTipsDialog(this); sqTipsDialog.setTile("提示").setMsg("是否确定借阅此书。书本借阅后需在一个月之内归还。") .setOnCanlceListener(new View.OnClickListener() { @Override public void onClick(View v) { sqTipsDialog.dismiss(); } }); sqTipsDialog.setOnSureListener(new View.OnClickListener() { @Override public void onClick(View v) { int new_inventory = bookArrayList.get(0).getinventory() - 1; bookTableHelper.BorrowBook(dbHelper,bid,new_inventory); Borrow borrow = new Borrow(); borrow.setBookid(bid); borrow.setUserid(uid); borrow.setBostate(0); GetTime getTime = new GetTime(); borrow.setBotime(getTime.BorrowTime()); borrowTableHelper.AddBorrow(dbHelper,borrow); sqTipsDialog.dismiss(); Intent intent = new Intent(BookActivity.this,BorrowSuccessActivity.class); intent.putExtra("bid",bid); startActivity(intent); } }); sqTipsDialog.show(); break; case R.id.collected: String uncollection = "/"+bid+"/"; String new_collection = collections.replace(uncollection,""); userTableHelper.CollectBook(dbHelper,uid,new_collection); collected.setVisibility(View.GONE); collect.setVisibility(View.VISIBLE); Toast.makeText(BookActivity.this,"取消收藏成功",Toast.LENGTH_SHORT).show(); break; case R.id.collect: String collection = "/"+bid+"/"; userTa解释代码

这段代码是一个 Android 应用程序中的一部分，它处理用户在图书页面上的...在这段代码中调用了一些自定义的方法和类，例如 SqTipsDialog、GetTime、BookTableHelper、Borrow、BorrowTableHelper、UserTableHelper 等。

//图书借出+1 public int BorrowAdd(Borrow r) { int ret = 0; try{ borCon.connectDB(); String sql1 = "select borrow from books where ISBN='" + r.getIsbn() + "'"; borCon.statement = borCon.connection.prepareStatement(sql1); borCon.resultSet = borCon.statement.executeQuery(sql1); int borrow = -1; if(borCon.resultSet .next()){ borrow = borCon.resultSet .getInt("borrow") + 1; } String sql2 = "update books set borrow='" + borrow + "' where ISBN='" + r.getIsbn() + "';"; borCon.statement = borCon.connection.prepareStatement(sql2); ret = borCon.statement.executeUpdate(sql2); } catch (SQLException throwable) { throwable.printStackTrace(); }finally { borCon.close(); } return ret; }翻译这段代码

这段代码定义了一个名为BorrowAdd的方法，其参数为一个Borrow对象，返回一个整数类型的值。该方法的作用是连接到数据库，首先执行查询语句以获取指定ISBN编号图书的借出数量，然后将其加1，最后再执行更新语句将借出...

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update book left join (select bno, count(*) as borrow_num from borrow where rdate is null group by bno) as borrow_count on book.bno = borrow_count.bno set book.available = coalesce(book.number, 0) - coalesce(borrow_count.borrow_num, 0);将该sql语句规范化

create trigger Book_return_Stock after update on Borrow for each row begin IF NEWselect.ReturnTime IS NOT NULL THEN UPDATE book SET Stock = Stock + 1 where BookID = New.BookID; end if; end; UPDATE Borrow SET ReturnTime = '2023-06-09' WHERE BookID = '1002' AND ReaderID = '20230101';

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