import java.io.BufferedReader;import java.io.FileReader;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.List;import java.util.Map;import java.util.TreeMap;import java.util.regex.Matcher;import
java.util.regex.Pattern;public
class WordsCounter { public
static void main(String[] args) throws
Exception { BufferedReader reader = new
BufferedReader(new
FileReader( "main.txt")); StringBuffer buffer = new
StringBuffer(); String line = null; while
((line = reader.readLine()) != null) { buffer.append(line); } reader.close(); Pattern expression = Pattern.compile("[a-zA-Z]+");// 定义正则表达式匹配单词 String string = buffer.toString(); Matcher matcher = expression.matcher(string);// Map<String, Integer> map = new
TreeMap<String, Integer>(); String word = ""; int
times = 0; // 是否匹配单词 while
(matcher.find()) { // 得到一个单词-树映射的键 word = matcher.group(); // 如果包含该键，单词出现过 if
(map.containsKey(word)) { // 得到单词出现的次数 times = map.get(word); map.put(word, times + 1); } else
{ // 否则单词第一次出现，添加到映射中 map.put(word, 1); } } /* * 排序 */ List<Map.Entry<String, Integer>> list = new
ArrayList<Map.Entry<String, Integer>>( map.entrySet()); /* * 定义排序规则，按照Entry的Value排序 */ Comparator<Map.Entry<String, Integer>> comparator = new
Comparator<Map.Entry<String, Integer>>() { public
int compare(Map.Entry<String, Integer> left, Map.Entry<String, Integer> right) { return
(left.getValue()).compareTo(right.getValue()); } }; // 利用Collections类的sort方法来排序，按照自定义的规则排序 Collections.sort(list, comparator); // 打印最多五个 int
last = list.size() - 1; for
(int i = last; i > last - 5; i--) { String key = list.get(i).getKey(); Integer value = list.get(i).getValue(); System.out.println(key + " :"
+ value); } }} |
原文：http://www.cnblogs.com/hubaoyue/p/3577447.html