System.out.print("Enter your guess(0to quit):"); guess=scan.nextInt(); scan.nextLine();是什么意思

这段代码是Java语言中的输入语句，用于读取用户在控制台中输入的信息。具体来说：

- `System.out.print("Enter your guess(0 to quit):");` 会在控制台中输出提示信息，告诉用户需要输入猜测的数字，以及在需要时可以输入0来退出程序。
- `guess=scan.nextInt();` 会读取用户输入的一个整数，并将其赋值给变量 `guess`。
- `scan.nextLine();` 用于读取输入行末的换行符，以便下一次输入可以从新的一行开始。

需要注意的是，如果用户输入的内容不是整数，则会抛出异常。因此在实际使用中，需要对输入进行合法性检查和异常处理。

相关问题

帮我修改一下我的代码错误：帮我看看我这段代码有什么错误：int choice = readPosInt("Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): "); // Perform the selected action while (choice != 6) { switch (choice) { case 1: System.out.println("Total number of borrowed books: " + Library.totalBorrowedBooks(null)); break; case 2: System.out.print("Type the user role (lender:1 borrower:2): "); int role = readPosInt(null); if (role == 1) { System.out.print("Enter the name of the user: "); String name = readLine(name); System.out.print("Enter the initial number of lent books: "); int numBooks = readPosInt(null); Lender lender = new Lender(name, numBooks); Library.addUser(lender); System.out.println("Lender "" + name + "" lending " + numBooks + " book(s) has been added."); } else if (role == 2) { System.out.print("Enter the name of the user: "); String name = readLine(name); System.out.print("Enter the initial number of borrowed books: "); int numBooks = readPosInt(null); Borrower borrower = new Borrower(name, numBooks); Library.addUser(borrower); System.out.println("Borrower "" + name + "" borrowing " + numBooks + " book(s) has been added."); } else { System.out.println("Unknown user role!"); } break; case 3: System.out.print("Enter the name of the user: "); String username = input.nextLine(); try { int numBorrowed = Library.totalBorrowedBooks(username); System.out.println(username + " borrows " + numBorrowed + " book(s)."); } catch (UnknownUserException e) { System.out.println("User " + username + " unknown."); } break; case 4: try { System.out.print("Enter the name of the user: "); String name = input.nextLine(); System.out.print("Enter the number of books: "); int num = input.nextInt(); input.nextLine(); library.moreBook(username, role); } catch (UnknownUserException e) { System.out.println("User " + username + " unknown."); } break; case 5: System.out.print("Enter the name of the user: "); username = input.next(); System.out.print("Enter the number of books: "); int numBooks = input.nextInt(); library.moreBook(username, -numBooks); // simulate decreasing books break; case 6: System.out.println("Goodbye!"); System.exit(0); break; }

在这段代码中，有几个错误需要修改：

1. 在第6行，readPosInt方法的参数为"Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): "，应该改为null。

2. 在第17行，Lender和Borrower的构造函数需要传入参数name和numBooks，应该改为lender和borrower。

3. 在第31行，input.nextLine()应该放在int role = readPosInt(null);的后面。

4. 在第37行，library应该改为Library。

5. 在第44行，input.next()应该改为input.nextLine()。

修改后的代码如下：

int choice = readPosInt(null);
// Perform the selected action
while (choice != 6) {
    switch (choice) {
        case 1:
            System.out.println("Total number of borrowed books: " + Library.totalBorrowedBooks(null));
            break;
        case 2:
            System.out.print("Type the user role (lender:1 borrower:2): ");
            int role = readPosInt(null);
            if (role == 1) {
                System.out.print("Enter the name of the user: ");
                String name = readLine(null);
                System.out.print("Enter the initial number of lent books: ");
                int numBooks = readPosInt(null);
                Lender lender = new Lender(name, numBooks);
                Library.addUser(lender);
                System.out.println("Lender " + name + " lending " + numBooks + " book(s) has been added.");
            } else if (role == 2) {
                System.out.print("Enter the name of the user: ");
                String name = readLine(null);
                System.out.print("Enter the initial number of borrowed books: ");
                int numBooks = readPosInt(null);
                Borrower borrower = new Borrower(name, numBooks);
                Library.addUser(borrower);
                System.out.println("Borrower " + name + " borrowing " + numBooks + " book(s) has been added.");
            } else {
                System.out.println("Unknown user role!");
            }
            break;
        case 3:
            System.out.print("Enter the name of the user: ");
            String username = input.nextLine();
            try {
                int numBorrowed = Library.totalBorrowedBooks(username);
                System.out.println(username + " borrows " + numBorrowed + " book(s).");
            } catch (UnknownUserException e) {
                System.out.println("User " + username + " unknown.");
            }
            break;
        case 4:
            try {
                System.out.print("Enter the name of the user: ");
                String name = input.nextLine();
                System.out.print("Enter the number of books: ");
                int num = input.nextInt();
                input.nextLine();
                Library.moreBook(name, num);
            } catch (UnknownUserException e) {
                System.out.println("User unknown.");
            }
            break;
        case 5:
            System.out.print("Enter the name of the user: ");
            username = input.nextLine();
            System.out.print("Enter the number of books: ");
            int numBooks = input.nextInt();
            input.nextLine();
            Library.moreBook(username, -numBooks); // simulate decreasing books
            break;
        case 6:
            System.out.println("Goodbye!");
            System.exit(0);
            break;
    }
    choice = readPosInt(null);
}

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 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;
}
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;
}
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.");
break;
} else {
System.out.println(names+" borrows " + (-5 + number -1) + "book(s).");
break;
}
} 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.");
break;
} else if(number>0||number<10){
System.out.println(names+" borrows " + (10 - number +1) + " book(s).");
break;
} 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).");
break;
}
} else {
System.out.println("User "+ names +" unknown.");
break;
}
default:
break;
}
}
}
}