Java以行的方式，快速读取大文件的2种实现方法，附完整代码和测试结果

Posted 2022-08-06 秋9

Java读取1272447行数据，存入List中，用时：396毫秒。

直接上代码，已做备忘。 

代码如下：

package com.example.springbootdownloadfile.file;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class ReadFileUtil 
    public static void main(String[] args) 
        long start=System.currentTimeMillis();
        String fileName="E:\\\\resource\\\\res2.txt";
        List<String> list=fileReadToArray(fileName);
        long start2=System.currentTimeMillis();
        System.out.println("读取"+list.size()+"行，用时："+(start2-start)+"毫秒");
        list=inputStreamReadertoArray(fileName);
        long start3=System.currentTimeMillis();
        System.out.println("读取"+list.size()+"行，用时："+(start3-start2)+"毫秒");
    
    public static List fileReadToArray(String filePath) 
        // 使用ArrayList来存储每行读取到的字符串
        List arrayList = new ArrayList<>();
        try 
            FileReader f = new FileReader(filePath);
            BufferedReader b = new BufferedReader(f);
            String s;
            //判断是否到一行字符串
            while ((s = b.readLine()) != null) 
                arrayList.add(s);
            
            b.close();
            f.close();
         catch (IOException e) 
            e.printStackTrace();
        
        return arrayList;

    
    public static List<String> inputStreamReadertoArray(String filePath) 
        List<String> arrayList = new ArrayList<>();
        try 
            File file = new File(filePath);
            InputStreamReader i = new InputStreamReader(new FileInputStream(file));
            BufferedReader b = new BufferedReader(i);
            // 按行读取字符串
            String s;
            while ((s = b.readLine()) != null) 
                arrayList.add(s);
            
            b.close();
            i.close();
         catch (IOException e) 
            e.printStackTrace();
        
        return arrayList;

    

测试结果：