Question

对于一些项目，我一直在尝试用Java创建一个类似于：

的控制台菜单

 (1) Do this
 (2) Do that
 (3) Blah blah
 (4) etc

我正在使用do {...} while (...)循环，但我无法获得控制变量的正确值。

我的代码是：

 String status = "e";

    do {
        System.out.println("---------------------------------------");
        System.out.println(b1.toString());
        System.out.println(b2.toString());
        System.out.println(b3.toString());
        System.out.println("---------------------------------------");
        System.out.println("Borrow(b), Return(r), Check(c), Exit(e)");
        status = r.nextLine();
        ....
    } while(!status.equals("e"));

此代码导致所有println输出正确，但按Enter键后，同样的内容将再次输出，而我用....替换的代码将不会执行。这段代码有其他控制台输出，从未出现过。

我认为这是因为r.nextLine()返回的值会随着新数据的输出而不断变化。所以我做了一个单独的static函数：

 public static String getInfo(Scanner r, Book b1, Book b2, Book b3) {
    System.out.println("---------------------------------------");
    System.out.println(b1.toString());
    System.out.println(b2.toString());
    System.out.println(b3.toString());
    System.out.println("---------------------------------------");
    System.out.println("Borrow(b), Return(r), Check(c), Exit(e)");
    String status = r.nextLine();
    return status;
}

但是这个函数也返回相同的结果。我该怎么做才能解决这个问题？

编辑：

现在，这是我的菜单部分的完整代码，它在主要部分运行。

`String status =“e”;

    do {
        status = getInfo(reader,b1,b2,b3);
        if (status == "b") {
            System.out.println("Which patron ( (1)" + p.getName() + " or (2)" + p2.getName() + " is borrowing?");
            int cur = reader.nextInt();
            System.out.println("Which book is " + cur + " borrowing?");
            String curbk = reader.nextLine();
            if (p.hasBook(curbk)){
                System.out.println(p.getName() + " has this book already.");
            } else {
                if (p2.hasBook(curbk)) {
                    System.out.println(p2.getName() + " has this book already.");
                } else {
                    if (cur==1) {
                        System.out.println(p.borrowBook(curbk));
                    } else {
                        System.out.println(p2.borrowBook(curbk));
                    }
                }
            }
        } else if (status == "r") {
            System.out.println("Which patron ( (1)" + p.getName() + " or (2)" + p2.getName() + ") is returning?");
            int cur = reader.nextInt();
            System.out.println("Which book is " + cur + " returning?");
            String curbk = reader.nextLine();
            if (cur==1) {
                if (p.hasBook(curbk)){
                    System.out.println(p.returnBook(curbk));
                } else {
                    System.out.println(p.getName() + " does not have this book.");
                }
            } else {
                if (p2.hasBook(curbk)){
                    System.out.println(p2.returnBook(curbk));
                } else {
                    System.out.println(p2.getName() + " does not have this book.");
                }
            }
        } else if (status == "c") {
            System.out.println("Which book would you like to check for?");
            String curbk = reader.nextLine();
            if (p.hasBook(curbk)){
                System.out.println(p.getName() + " has this book.");
            } else {
                if (p2.hasBook(curbk)) {
                    System.out.println(p2.getName() + " has this book.");
                } else {
                    System.out.println("This book is ready to be checked out!");
                }
            }
        }
    } while(!status.equals("e"));`

getInfo()来自上方。

Answer 1

String status = r.nextLine();

删除关键字String，因为它创建了一个新的String而不是使用您已创建的变量。

无法使控制台菜单正常运行

1 个答案: