Question

public class TestLibraryBook {

    public static void main(String[] args) {
        LibraryBook book1, book2;
        book2 = new LibraryBook("Ali's book", "Ali", "1st June", 250);
        book1 = book2;
        LibraryBook book5, book6;
        LibraryBook book3, book4;
        LibraryBook book7, book8, book9, book10;
        book4 = new LibraryBook("David's Labs", "David", "29 of February", 1);
        book3 = book4;
        book6 = new LibraryBook("James adventure", "James", "May", 25);
        book5 = book6;

        book7 = new LibraryBook("James holiday", "Jane", "Jun", 31);
        book8 = book7;
        book9 = new LibraryBook("James holiday", "Jane", "April", 53);
        book10 = book9;
    }
}

这是我的第二堂课

public class LibraryBook {
    // variables
    public String title;
    public String author;
    public String dueDate;
    public int timesLoaned;

    // constructor
    public LibraryBook(String title, String author, String dueDate, int timesLoaned) {
        this.title = title;
        this.author = author;
        this.dueDate = dueDate;
        this.timesLoaned = timesLoaned;

    }
    // constructor

    public LibraryBook() {
        title = "no info";
        author = "no info";
        dueDate = " no info ";
        timesLoaned = 0;
    }

    public boolean equals() {
        if (title.equals(title) & author.equals(author)) {
            return true;
        }
        return false;
    }
}

我有两个带有对象和引用的类，我想说一下它们的title和author是否相同。因此，我想在我的boolean equals类中添加LibraryBook方法，以便将具有相同title和author的书籍视为相同的书籍，而不考虑其dueDate或timesLoaned。我无法做到这一点，请帮助我。

Answer 1

如果您不是Netbeans，则只需右键单击您的类，然后生成代码，等于和哈希代码，然后仅选择标题，Netbeans将为您自动生成该方法。方法的问题在于，您正在将对象与其自身进行比较，您需要接收另一个LibraryBook作为参数并比较2。

    public boolean equals(LibraryBook other)
{
    if(this.title.equals(other.title) && this.author.equals(other.author))
    {
        return true;
    }
    return false;

    }
}

Answer 2

编写equals方法如下：

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    LibraryBook other = (LibraryBook) obj;
    if (author == null) {
        if (other.author != null)
            return false;
    } else if (!author.equals(other.author))
        return false;
    if (title == null) {
        if (other.title != null)
            return false;
    } else if (!title.equals(other.title))
        return false;
    return true;
}

我如何添加此.equals（）方法

2 个答案: