用JavaIO，正则表达式，HashMap统计一个文本单词数量

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.HashMap;



public class WordCount {
    public static void main(String[] args) {
        HashMap<String, Integer>mp = new HashMap<>();
        mp.put("jack", 1);
        mp.put("Tom", 2);
        mp.put("rose", 3);
        mp.put("jack",4);
        
            
//        System.out.println(mp);
//        System.out.println(mp.size());
//        System.out.println(mp.keySet());
//        System.out.println(mp.values());
        
        try (BufferedReader in = new BufferedReader(new FileReader("filetest.txt"))
            ){
            String line;
            int c = 0;
            while(null != (line = in.readLine())) {
                
                String[] words = line.split("\W");//单词的边界                
                for(String w : words) {
                    if(w.trim().length() == 0) continue;
//                    if(w.trim().length() == 1) {
//                        //长度为1
//                        char cc = w.charAt(0);
//                        if(!Character.isLetterOrDigit(c)) {
//                            continue;
//                        }
//                    }
                    w = w.toLowerCase();//不分大小写的统计                    
                    if(!mp.containsKey(w)) {
                        mp.put(w, 1);
                    }else {
                        int n = mp.get(w);
                        mp.put(w, n+1);
                    }                    
                }
                
            }
            
            for(String key : mp.keySet()) {
                int v = mp.get(key);
                System.out.printf("%s	%d
",key,v);
            }
            
        } catch (Exception e) {
            // TODO: handle exception
        }
    }
}

 输出：

常见的正则表达式符号：