大文本文件读取实验

大文本文件是用此文的方法生成的。

读取程序较简单，无需赘述，贴于此地以备考：

package readwritefile;

import java.io.BufferedReader;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class BigFileReader {
    public static void main(String[] args) {
        long startMs=System.currentTimeMillis();
        Path filepath=Paths.get("c:\\temp\\20200229.txt");
        Charset u8set=Charset.forName("utf-8");
        
        try(BufferedReader reader=Files.newBufferedReader(filepath, u8set)){
            String line="";
            
            int max=-1;
            do {
                line=reader.readLine();
                
                try {
                    int num=Integer.parseInt(line);
                    
                    if(num>max) {
                        max=num;
                    }
                    
                }catch(NumberFormatException ex) {
                    break;
                }
                
            }while(line!=null);
            
            System.out.println("The biggest number is "+ max);
        }catch(IOException ex) {
            ex.printStackTrace();
        }
        
        long endMs=System.currentTimeMillis();
        System.out.println("File:'"+filepath+"' created,time elapsed:"+ms2DHMS(startMs,endMs));
    }
    
    /**
     * change seconds to DayHourMinuteSecond format
     * 
     * @param startMs
     * @param endMs
     * @return
     */
    private static String ms2DHMS(long startMs, long endMs) {
        String retval = null;
        long secondCount = (endMs - startMs) / 1000;
        String ms = (endMs - startMs) % 1000 + "ms";

        long days = secondCount / (60 * 60 * 24);
        long hours = (secondCount % (60 * 60 * 24)) / (60 * 60);
        long minutes = (secondCount % (60 * 60)) / 60;
        long seconds = secondCount % 60;

        if (days > 0) {
            retval = days + "d" + hours + "h" + minutes + "m" + seconds + "s";
        } else if (hours > 0) {
            retval = hours + "h" + minutes + "m" + seconds + "s";
        } else if (minutes > 0) {
            retval = minutes + "m" + seconds + "s";
        } else if(seconds > 0) {
            retval = seconds + "s";
        }else {
            return ms;
        }

        return retval + ms;
    }
}

输出：

The biggest number is 99999991
File:'c:\temp\20200229.txt' created,time elapsed:126ms

--2020年2月29日--