1,拿到 API 文档

登录 https://docs.oracle.com/javase/8/docs/api/

选中特定的类,然后 copy 其中的内容,

1545827963474.png

放入 TXT 文件中 ,

1545828104822.png

2,读取TXT内容,并排序

package com.lgx.test;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;

public class ReadVectorAPI {

    public static String filename = "src/Vector.txt";
    public static StringBuffer sb = null;

    public static void main(String[] args) {
        try {
            //根据单词字母排序
            countWordOrderByWord();
            //根据单词频率排序
            countWordOrderByCount();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    // 计算单词的出现次数,依据单词排序
    public static void countWordOrderByWord() throws FileNotFoundException {
        BufferedReader br = null;
        try {
            br = new BufferedReader(new FileReader(new File(filename)));
            String inputLine = null;
            TreeMap<String, Integer> map = new TreeMap<String, Integer>();
            while ((inputLine = br.readLine()) != null) {
                String[] words = inputLine.split("[ \n\t\r.,;:!?(){}]");
                for (int i = 0; i < words.length; i++) {
                    String key = words[i].toLowerCase();
                    if (key.length() > 0) {
                        if (map.get(key) == null) {
                            map.put(key, 1);
                        } else {
                            int times = map.get(key).intValue();
                            times++;
                            map.put(key, times);
                        }
                    }
                }
            }
            Set<Map.Entry<String, Integer>> entrySet = map.entrySet();
            System.out.println("=====根据单词字母排序=====");
            for (Map.Entry<String, Integer> entry : entrySet) {
                System.out.println(entry.getKey() + " 在API文档中出现了 " + entry.getValue() + " 次");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 计算单词的出现次数,依据次数排序
    public static void countWordOrderByCount() throws FileNotFoundException {
        BufferedReader br = null;
        try {
            br = new BufferedReader(new FileReader(new File(filename)));
            String inputLine = null;
            TreeMap<String, Integer> map = new TreeMap<String, Integer>();
            while ((inputLine = br.readLine()) != null) {
                String[] words = inputLine.split("[ \n\t\r.,;:!?(){}]");
                for (int i = 0; i < words.length; i++) {
                    String key = words[i].toLowerCase();
                    if (key.length() > 0) {
                        if (map.get(key) == null) {
                            map.put(key, 1);
                        } else {
                            int times = map.get(key).intValue();
                            times++;
                            map.put(key, times);
                        }
                    }
                }
            }

            List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(map.entrySet());
            Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
                public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
                    return o2.getValue().compareTo(o1.getValue());
                }
            });
            System.out.println("=====根据单词频率排序=====");
            for (Map.Entry<String, Integer> mapping : list) {
                System.out.println(mapping.getKey() + " 在API文档中出现了 " + mapping.getValue() + " 次");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

输出结果前部分截图为;

1545828218319.png