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对于书籍数组，任务是从用户那里获取对象的属性，然后根据他们选择的作者、标题或页数进行排序。我的冒泡排序适用于页数，但不适用于用户选择作者或标题时，所以我猜我在参考存储和值存储方面缺少一些东西，也许？谢谢！

import javax.swing.*;
import java.util.*;
public class LibraryBookSort {

public static void main(String[] args) {
    LibraryBook[] books = new LibraryBook[5];
    LibraryBook tempBook = new LibraryBook();
    String enteredAuthor = "", enteredTitle = "";
    String enteredPageCount;
    String sortBy;
    String displayString = "";
    int parsedSortBy;
    int parsedPageCount;
    int booksLength = books.length;

    // populate the array
    for (int x = 0; x < booksLength; ++x)
        books[x] = new LibraryBook();

    // get property values from user
    for (int x = 0; x < booksLength; ++x)
    {
        enteredTitle = JOptionPane.showInputDialog(null, "Enter book " + (x + 1) + " of 5's title:");
        books[x].setTitle(enteredTitle);
        enteredAuthor = JOptionPane.showInputDialog(null, "Enter book " + (x + 1) + " of 5's author:");
        books[x].setAuthor(enteredAuthor);
        enteredPageCount = JOptionPane.showInputDialog(null, "Enter book " + (x + 1) + " of 5's page count:");
        parsedPageCount = Integer.parseInt(enteredPageCount);
        books[x].setPageCount(parsedPageCount);
    }

    // sort by property values
    sortBy = JOptionPane.showInputDialog("Choose option to sort by: (1) title, (2) author, or (3) page count");
    parsedSortBy = Integer.parseInt(sortBy);

    while (parsedSortBy < 1 || parsedSortBy > 3)
    {
        sortBy = JOptionPane.showInputDialog("Invalid selection, please choose option to sort by: (1) title, (2) author, or (3) page count");
        parsedSortBy = Integer.parseInt(sortBy);
    }

    if (parsedSortBy == 1)
    {
        for (int a = 0; a < booksLength - 1; ++a)
        {
            for (int b = 0; b < booksLength - 1; ++b)
            {
                if (books[b].getTitle().compareTo(books[b+1].getTitle()) > 1)
                {
                    tempBook = books[b];
                    books[b] = books[b+1];
                    books[b+1] = tempBook;
                }
            }
        }
    }
    else if (parsedSortBy == 2)
    {
        for (int a = 0; a < booksLength - 1; ++a)
        {
            for (int b = 0; b < booksLength - 1; ++b)
            {
                if (books[b].getAuthor().compareTo(books[b+1].getAuthor()) > 1)
                {
                    tempBook = books[b];
                    books[b] = books[b+1];
                    books[b+1] = tempBook;
                }
            }
        }
    }
    else
    {
        for (int a = 0; a < booksLength - 1; ++a)
        {
            for (int b = 0; b < booksLength - 1; ++b)
            {   
                if (books[b].getPageCount() > books[b+1].getPageCount())
                {
                    tempBook = books[b];
                    books[b] = books[b+1];
                    books[b+1] = tempBook;
                }
            }
        }
    }

    for (int i = 0; i < booksLength; ++i)
    {
        displayString += (books[i].getTitle() + ", by " + books[i].getAuthor() + ". " + books[i].getPageCount() + " pages.\n");
    }
    JOptionPane.showMessageDialog(null, "Books sorted by your choice:\n\n" + displayString);
}

}

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2 回答 2

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由于您使用的是 compareTo 方法进行排序，因此您必须知道 compareTo 取决于字典顺序。

oracle docs引用如下，这是字典顺序的定义。如果两个字符串不同，则它们在某个索引处具有不同的字符，该索引是两个字符串的有效索引，或者它们的长度不同，或两者兼而有之。如果它们在一个或多个索引位置具有不同的字符，则设 k 为此类索引中的最小；然后，在位置 k 处的字符具有较小值的字符串（通过使用 < 运算符确定）按字典顺序位于另一个字符串之前。在这种情况下，compareTo 返回两个字符串中位置 k 处的两个字符值的差值——即值：

this.charAt(k)-anotherString.charAt(k)

如果它们没有不同的索引位置，则较短的字符串按字典顺序位于较长的字符串之前。在这种情况下， compareTo 返回字符串长度的差值——即值：this.length()-anotherString.length()

于 2013-09-10T05:39:19.543 回答
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比较应该是

.... > 0

不是

.... > 1

的合同compareTo是在相等时返回零，对于“较大”返回 >0，对于“较小”返回 <0。实际上，这些值为 -1、0 和 +1。

于 2013-09-10T05:39:30.683 回答