Java---统计单词个数

Posted 2021-06-15 Shall潇

一、单线程统计

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Map;
import java.util.TreeMap;

/**
 * @Author shall潇
 * @Date 2021/5/31
 * @Description   单线程读文件统计单词个数
 */
public class wc1 {
    public static void main(String[] args) {
        Map<String,Integer> map = new TreeMap<>();		  		//用于存放最后结果
        try {
            BufferedReader buff = new BufferedReader(new FileReader("word.txt")); //IO流读取数据
            String tmp = "";
            while ((tmp=buff.readLine())!=null){
            	if(!tmp.equals("")){							  //防止读到空行
	                String[] strs = tmp.trim().split(" ");
	                for (int i = 0; i < strs.length; i++) {
	                    if(map.containsKey(strs[i])){
	                        map.put(strs[i],map.get(strs[i])+1);  //如果这个单词已经出现过，数量+1
	                    }else {
	                        map.put(strs[i],1);                   //如果第一次单词出现，直接放入
	                    }
	                }
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        //遍历打印单词和个数
        map.forEach((k,v)->{
            System.out.println("单词："+k+":"+v);
        });
    }
}

二、多线程统计

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * @Author shall潇
 * @Date 2021/5/31
 * @Description  多线程统计单词个数：每个线程统计好，最后累计一下，相当于先组内统计，在再组间统计
 */
public class wc2 {
    //String:线程名，Map<String,Integer>:String:单词，Integer:个数
    static Map<String,Map<String,Integer>> threadMap = new ConcurrentHashMap<>();
    //创建线程池
    static ExecutorService executorService = Executors.newCachedThreadPool();

    public static void threadConf(String content,Integer count){          //执行线程
        wcThread wcThread = new wcThread(content);                        //wcThread 类在最后面定义
        Thread thread = new Thread(wcThread);
        executorService.execute(thread);
        threadMap.put("thread-"+count,wcThread.wordMap);
    }

    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new FileReader("word.txt"));
            String tmpStr = "";
            StringBuffer lineStringBuf = new StringBuffer();
            int num = 0;
            while ((tmpStr=br.readLine())!=null){
                if(!tmpStr.equals("")){
                    num++;                  //每读一行，统计一下
                    lineStringBuf.append(tmpStr.trim()+" ");
                    if(num%30000==0){       //每读3万行，启动一个线程
                        threadConf(lineStringBuf.toString(),num/30000); //启动线程
                        lineStringBuf.delete(0,lineStringBuf.length());        //清空buffer缓存
                    }
                }
            }
            //最后不足30000行的数据
            if(lineStringBuf.length()>0){
                threadConf(lineStringBuf.toString(),0);
                lineStringBuf.delete(0,lineStringBuf.length());
            }

            executorService.shutdown();    //关闭线程池，有可能主线程结束，子线程还没运行完

            while (true){
                if(executorService.isTerminated()){         //确保所有子线程都运行完了
                    ConcurrentHashMap<String, Integer> chMap = new ConcurrentHashMap<>();  //最终结果保存的地方
                    for (Map<String, Integer> value : threadMap.values()) {
                        value.forEach((k,v)->{
                            if(chMap.containsKey(k)){
                                chMap.put(k,chMap.get(k)+value.get(k));         //将线程统计的单词个数在总体统计
                            }else {
                                chMap.put(k,value.get(k));
                            }
                        });
                    }
                    chMap.forEach((k,v)->{
                        System.out.println("单词："+k+":"+v);
                    });
                    break;
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
class wcThread implements Runnable{

    String content = "";            //读到的每一行
    Map<String,Integer> wordMap = new TreeMap<>();

    public wcThread(String content) {
        this.content = content;
    }

    @Override
    public void run() {
        String[] strs = content.trim().split(" ");
        for (int i = 0; i < strs.length; i++) {
            if(wordMap.containsKey(strs[i])){
                wordMap.put(strs[i],wordMap.get(strs[i])+1);
            }else {
                wordMap.put(strs[i],1);
            }
        }
    }
}