java - 缺少返回语句方法ReturnCopy

Question

我创建了这个方法，但我不确定为什么它说缺少返回语句。我需要将打印更改为返回吗？ (这是最底部的方法)我是一个 Java 初学者，所以任何帮助将不胜感激!

public class Book {
private String title;
private String author;
private int copies;
private boolean borrowed;


public Book( String inAuthor, String inTitle, int inNumberOfCopies ) {
    this.author = inAuthor;
    this.title = inAuthor;
    this.copies = inNumberOfCopies;

}

 public void borrowed() {
    borrowed = true;
}

public void rented() {
    borrowed = true;
}

public void returned() {
    borrowed = false;
}

public boolean isBorrowed() {
    return borrowed;
}

public String getAuthor() {
    return this.author;

}

public static String getTitle() {
    return getTitle();

}

public int getTotalCopies() {
    return this.copies;

}

public int getAvailableCopies() {

}

public void withdrawCopy() {
        int found = 0;
for (Book b : Library.getListOfBooks()) {
    if (b.getTitle().equals(title)) {
       if (found == 0) {
        found = 1;
    }
    if (!b.isBorrowed()) {
        b.borrowed=true;
        found = 2;
        break;      
        }
     if (found == 0) {
        System.out.println("Sorry, this book is not in our catalog.");
    } else if (found == 1) {
        System.out.println("Sorry, this book is already borrowed.");
    } else if (found == 2) {
        System.out.println("You successfully borrowed " + title);
    }
    }

    }

}

public String returnCopy() {
    boolean found = false;
    for (Book book : Library.getListOfBooks()) {
        if (getTitle().equals(title) && book.isBorrowed()) {
            book.returned();
            found = true;
        }
        if (found) {
        System.out.println("you successfully returned " + title);
    }
    }
}
}

Answer 1

public String returnCopy()

public 后面的

String 表示该方法将返回一个 String。您的 public String returnCopy() 当前未返回任何内容。

如果你不想返回任何东西，你可以像这样使用void:

public void returnCopy(){
    // code
}

与 public int getAvailableCopies() 存在同样的问题，这应该返回一个 int 但您没有返回任何内容。

小心:

这个方法:

public static String getTitle() {
    return getTitle();
}

是一种没有基本条件的递归方法。这将导致错误并迫使您的应用程序崩溃。