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我有点困惑,哪些实用程序类可用于此类问题:
我有一个包含以下信息的文件 Movies.txt:Id, Name, Director, Rating. 评级可能存在也可能不存在。

样本:

1,ABC,Mr. xyz,4.5
3,GHI,Mr. mno
2,DEF,Ms. stu,3

我需要读取这个文件并将其存储到内存中,然后应用 sort byrating以及 byname然后稍后写入文件。在这种情况下,哪个实用程序类可以最好地帮助我,以便在可能的情况下轻松执行此操作。没有更多的文件可以使用。

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3 回答 3

1

好的,答案已被接受,但我有权不持相同意见。

Comparable 应该根据它们的整个状态反映 2 个对象之间的关系(当然,跳过了 ids 和其他不相关的字段)。如果您想按部分状态(几个字段)对某些对象进行排序,您应该使用Comparator

于 2013-10-04T08:55:04.603 回答
1

您需要一次读取此输入文件一行,通过在“,”处拆分来解析每一行,构造一个 Movie 对象(您定义的)并添加到某种数组/映射/集合中。然后按照说明对你的array/map/set进行排序,并写出响应文件。

做一些研究:

  • 从文件中读取行
  • 使用 split 解析字符串
  • 列表、地图
  • 排序(比较)
于 2013-10-04T03:49:25.033 回答
1

首先定义一个Object描述“电影”基本属性的 。让您的生活更轻松,implement Comparable<Movie>直接这样做可能是个好主意。

public class Movie implements Comparable<Movie> {

    private int id;
    private String name;
    private String directory;
    private double rating;

    public Movie(int id, String name, String directory, double rating) {
        this.id = id;
        this.name = name;
        this.directory = directory;
        this.rating = rating;
    }

    public int getId() {
        return id;
    }

    public String getDirectory() {
        return directory;
    }

    public String getName() {
        return name;
    }

    public double getRating() {
        return rating;
    }

    @Override
    public int compareTo(Movie o) {
        int diff = (int) asInt(getRating()) - asInt(o.getRating());
        if (diff == 0) {
            diff = getName().compareTo(name);
        }
        return diff;
    }

    protected int asInt(double value) {
        String text = Double.toString(value);
        text = text.replaceAll("\\.", "");
        return Integer.parseInt(text);
    }

    @Override
    public String toString() {
        return getId() + ", " + getName() + ", " + getDirectory() + ", " + getRating();
    }

}

创建一个List来保存传入的电影

List<Movie> movies = new ArrayList<Movie>(25);

阅读内容并将每一行解析为它们单独的属性元素(我会留下你),将每个新创建的内容添加Movie到列表中......

movies.add(new Movie(...));

用于Collections.sort(movies)对它们进行排序...

例如...

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class SortExample {

    public static void main(String[] args) {
        List<Movie> movies = new ArrayList<Movie>(5);
        movies.add(new Movie(1, "ABC", "Mr. xyz", 4.5));
        movies.add(new Movie(2, "GHI", "Mr. mno", 0));
        movies.add(new Movie(3, "DEF", "Ms. stu", 3));
        movies.add(new Movie(4, "AT1", "Mr. T", 3));

        System.out.println("Before....");
        for (Movie movie : movies) {
            System.out.println(movie);
        }

        Collections.sort(movies);

        System.out.println("After....");
        for (Movie movie : movies) {
            System.out.println(movie);
        }

    }

    public static class Movie implements Comparable<Movie> {

        private int id;
        private String name;
        private String directory;
        private double rating;

        public Movie(int id, String name, String directory, double rating) {
            this.id = id;
            this.name = name;
            this.directory = directory;
            this.rating = rating;
        }

        public int getId() {
            return id;
        }

        public String getDirectory() {
            return directory;
        }

        public String getName() {
            return name;
        }

        public double getRating() {
            return rating;
        }

        @Override
        public int compareTo(Movie o) {
            int diff = (int) asInt(getRating()) - asInt(o.getRating());
            if (diff == 0) {
                diff = getName().compareTo(name);
            }
            return diff;
        }

        protected int asInt(double value) {
            String text = Double.toString(value);
            text = text.replaceAll("\\.", "");
            return Integer.parseInt(text);
        }

        @Override
        public String toString() {
            return getId() + ", " + getName() + ", " + getDirectory() + ", " + getRating();
        }

    }

}
于 2013-10-04T03:59:12.247 回答