我正在为家庭作业写一本书店计划。该程序为用户提供了6种不同的选项供他们选择。目前，我正在研究的是选项1.选项1是为库存添加更多书籍。当用户选择选项1时，它要求用户输入书名，然后检查书籍是否已经存货。我遇到的问题是检查用户输入的书名是否已经存货。我有一个名为inStock的函数，但我不确定如何调用这个函数。现在代码无法编译，因为我在if (bt == myBkStore.inStock(title, y))行显示错误，因为类型不兼容。但我不知道如何调用inStock（）函数。到目前为止，这是我的编码：
import java.util.Scanner;
import java.util.ArrayList;
public class MyBookstore {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
Bookstore myBkStore = new Bookstore();
int y = 0;
int user_choice = 2;
boolean quit = false;
do {
//display menu to user
//ask user for his choice and validate it (make sure it is between 1 and 6)
System.out.println();
System.out.println("1) Add a book to the stock");
System.out.println("2) Sell a book in stock");
System.out.println("3) List the titles of all the books in stock (in the Bookstore object)");
System.out.println("4) List all the information about the books in stock (in the Bookstore object)");
System.out.println("5) Print out the gross income of the bookstore");
System.out.println("6) Quit");
System.out.println();
System.out.print("Enter choice [1-6]: ");
user_choice = s.nextInt();
switch (user_choice) {
case 1: System.out.println("Enter a book title");
String bt = s.next(); //stores title of book user enters in
if (myBkStore.inStock(title, y))
{
System.out.println("How many more to add to the stock");
y = s.nextInt();
myBkStore.addBookQuantity(bt, y);
}
else
{
System.out.println("Enter the amount of pages of the book: ");
int pages = s.nextInt();
System.out.println("Enter the price of the book: ");
double price = s.nextDouble();
System.out.println("Enter the quantity to add: ");
int quant = s.nextInt();
//myBkStore.Book(bt, pages, price, quant);
myBkStore.addNewBook(book);
}
break;
case 2: System.out.println("Enter book title to buy: ");
String bookT = s.next();
myBkStore.sellBook(title, y);
break;
case 3: myBkStore.listTitles();
break;
case 4: myBkStore.listBooks();
break;
case 5: myBkStore.getIncome();
break;
case 6: System.out.println("Thanks for coming");
quit = true;
break;
default: System.out.println("\nInvalid Choice");
}
}
while (!quit);
}
static class Bookstore {
private Book[] books; // all the books in this bookstore
private int totalBooks; // the number of books in this bookstore
private double grossIncome; //the gross income of the bookstore (will be incremented when books are sold)
// Constructor: A new Bank object initially doesn’t contain any accounts.
public Bookstore() {
books = new Book[100];
totalBooks = 0;
grossIncome = 0;
}
// Creates a new bank account using the customer name and the opening balance given as parameters
// and returns the account number of this new account. It also adds this account into the account list
// of the Bank calling object.
public void addNewBook(Book b) {
if(totalBooks < books.length) {
books[totalBooks] = b;
totalBooks++;
}
else
{
System.out.println("\nSorry, cannot add book to stock.");
}
}
public void addBookQuantity(String title, int quantity) {
for (int i =0; i<totalBooks; i++) {
if (title == books[i].getTitle() ) {
books[i].addQuantity(quantity);
System.out.println("Quantity added successfully");
return;
}
}
/*int i;
for (i = 0; i < totalbooks; i++)
{
if((books[i].getTitle()).equals(title))
{
books[i].addQuantity(quantity);
return;
}
}*/
}
public boolean inStock (String title, int quantity) {
for (int i =0; i<totalBooks; i++) {
if (title.equals(books[i].getTitle())) {
if (quantity <= books[i].getQuantity()) {return true;}
else {return false;}
}
}
return false;
}
public boolean sellBook(String title, int quantity){
int i;
boolean sellflag=false;
// Checks to see if the books are in stock.
boolean retval = inStock(title, quantity);
// If so, completes the sale.
if (retval) {
for (i=0; i<totalBooks && !sellflag; i++) {
if (title.equals(books[i].getTitle())) {
books[i].subtractQuantity(quantity);
grossIncome += (books[i].getPrice()) * quantity;
sellflag = true;
}
} // for
} // if
return retval;
} // sellBook
public void listTitles()
{
for (int i = 0; i < totalBooks; i++)
{
System.out.println(books[i].getTitle());
}
}
public void listBooks()
{
int i;
System.out.println("\nList of Books\n======");
for (i = 0; i < totalBooks; i++)
{
System.out.println(books[i]);
}
System.out.println();
}
public double getIncome()
{
return grossIncome;
}
}
static class Book{
private String title;
private int numOfPages;
private double price;
private int quantity;
private Book book;
public String toString(){
return "Title: " + title + "\nNumber of pages: " + numOfPages + "\nPrice:" + price +"\nQuantity: " + quantity + "\n";
}
public Book book(String thetitle, int pages, double cost, int num){
/*title = thetitle;
numOfPages = pages;
price = cost;
quantity = num;*/
return book;
}
public String getTitle(){
return title;
}
public double getPrice(){
return price;
}
public int getQuantity(){
return quantity;
}
public void addQuantity(int amount){
quantity = quantity + amount;
}
public void subtractQuantity(int amount)
{
System.out.println("Amount to buy");
Scanner s = new Scanner(System.in);
quantity = s.nextInt();
quantity = quantity - amount;
}
}//end of class
}
答案 0 :(得分：2)
bt是一个字符串。 inStock方法的返回类型是布尔值。您需要将inStock的返回值存储为布尔值。然后在if语句中使用从inStock方法返回的内容。例如：
if (myBkStore.inStock(title, y)) { // this statement basically means if (myBkStore.inStock(title, y) == true)
// then do stuff
}
OR
if (!myBkStore.inStock(title, y)) { // this statement basically means if (myBkStore.inStock(title, y) == false)
// then do stuff
}
答案 1 :(得分：2)
bt是一个字符串：
String bt = s.next();
但是inStock（）返回一个布尔值：
public boolean inStock(...)
所以当你打电话时：
if (bt == myBkStore.inStock(title, y))
你说“如果这个字符串（bt）等于这个布尔值（由inStock返回）”......
此处的类型不兼容，因此异常
编辑：要简单检查inStock是返回true还是false，您只需说：
if (myBkStore.inStock(title, y))
// do stuff you want to do if the inStock() method returns true
else
//do stuff you want to do if the inStock() method returns false
注意：(myBkStore.inStock(bt, y))是一种简短的说法
if (myBkStore.instock(title, y) == true)
答案 2 :(得分：0)
Jus尝试替换
if (bt == myBkStore.inStock(title, y))
使用：
if (myBkStore.inStock(bt, y))
答案 3 :(得分：0)
只需从代码中删除bt ==即可。它应该工作
if (myBkStore.inStock(title, y))
{
System.out.println("How many more to add to the stock");
y = s.nextInt();
myBkStore.addBookQuantity(bt, y);
}