java - 根据比较器使用字符串日期排序？

Question

我有以下类(class):

public class Book implements Cloneable {
    private int ISBN;
    private String title;
    private String publishDate;
    private int pageCount;
}

我可以使用以下代码根据 Comparator 进行排序:

Comparator<Book> titleComparator = new Comparator<Book>() {
    @Override
    public int compare(Book o1, Book o2) {
        return o1.title.compareTo(o2.title);
    }
};

Comparator<Book> ISBNComparator = new Comparator<Book>() {
    @Override
    public int compare(Book o1, Book o2) {
        return Integer.valueOf(o1.ISBN).compareTo(o2.ISBN);
    }
};

public void sort(final String field, ArrayList<Book> BookList) {
    final Comparator<Book> comparator;

    if (field.equals("title")) {
        comparator = titleComparator;
    } else if (field.equals("ISBN")) {
        comparator = ISBNComparator;
    } else {
        throw new IllegalArgumentException("Comparator not found for " + field);
    }

    Collections.sort(BookList, comparator);
}

但是当发布日期格式为“25/12/2015”时，如何根据字符串 publishDate 进行排序？

Answer 1

如果您确定不能选择使用 Date 而不是 String，请使用此比较器(您可以添加一些缓存以避免每次都解析字符串):

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Comparator;

/**
 *
 * @author EBudaqov
 */
public class StringDateComparator implements Comparator<String>{

    private SimpleDateFormat formatter;

    public StringDateComparator(String dateFormat) {
        formatter = new SimpleDateFormat(dateFormat);
    }

    @Override
    public int compare(String s1, String s2) {
        try {
            return formatter.parse(s1).compareTo(formatter.parse(s2));
        } catch(ParseException exception) {
            throw new RuntimeException(exception);
        }
    }

    public static void main(String[] args) {
        String s1 = "01/01/2015";
        String s2 = "02/01/2015";

        System.out.println(new StringDateComparator("dd/MM/yyyy").compare(s1, s2));
    }

}