Java文件操作类效率介绍

前言
ASP站长网众所周知，Java中有多种针对文件的操作类，以面向字节流和字符流可分为两大类，这里以写入为例：
 
面向字节流的：FileOutputStream 和 BufferedOutputStream
 
面向字符流的：FileWriter 和 BufferedWriter
 
近年来发展出New I/O ，也叫NIO，里面又包装了两个类：NewOutputStream 和 NewBufferedWriter
 
现在，我们建立测试程序，比较这些类写入文件的性能。
 
机器配置
Processor Name: Intel Core i7
Processor Speed: 2.2 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 16 GB
测试程序
纵向比较：几种文件操作类向文件中写入相同行数的内容（每行内容均为“写入文件Data\n”），比较其耗费时间
 
横向比较：对于同一个文件操作类，比较写入不同行数内容情况下所耗费时间；本文以2的次方指数级增长行数
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.*;
import java.nio.file.Files;
import java.nio.file.Paths;
 
public class testFileIO {
 
    public static void testDriver () throws IOException {
        int maxlineNum = 100000001;//写入文件的最大行数
        int startlineNum = 1;//写入文件的行数
        int Multiplying = 2;//行数增长倍率
 
        long begin = 0L;
        long end = 0L;
 
        //将时间统计写入文件Result.txt中
        FileWriter fileWriter = new FileWriter("./Result.txt", true);
        BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
 
        System.out.println("Test FileOutputStream begin.");
        for (int lineNum = startlineNum; lineNum < maxlineNum; lineNum *= Multiplying) {
            begin = System.currentTimeMillis();
            testFileOutputStream(lineNum);
            end = System.currentTimeMillis();
            long timeElapse_FileOutputStream = end - begin;
            bufferedWriter.write(String.valueOf(timeElapse_FileOutputStream)+"\t");
        }
        System.out.println("Test FileOutputStream end.\n");
 
        System.out.println("Test BufferedOutputStream begin.");
        bufferedWriter.write("\n");
        for (int lineNum = startlineNum; lineNum < maxlineNum; lineNum *= Multiplying) {
            begin = System.currentTimeMillis();
            testBufferedOutputStream(lineNum);
            end = System.currentTimeMillis();
            long timeElapse_BufferedOutputStream = end - begin;
            bufferedWriter.write(String.valueOf(timeElapse_BufferedOutputStream)+"\t");
        }
        System.out.println("Test BufferedOutputStream end.\n");
 
        System.out.println("Test FileWriter begin.");
        bufferedWriter.write("\n");
        for (int lineNum = startlineNum; lineNum < maxlineNum; lineNum *= Multiplying) {
            begin = System.currentTimeMillis();
            testFileWriter(lineNum);
            end = System.currentTimeMillis();
            long timeElapse_FileWriter = end - begin;
            bufferedWriter.write(String.valueOf(timeElapse_FileWriter)+"\t");
        }
        System.out.println("Test FileWriter end.\n");
 
        System.out.println("Test BufferedWriter begin.");
        bufferedWriter.write("\n");
        for (int lineNum = startlineNum; lineNum < maxlineNum; lineNum *= Multiplying) {
            begin = System.currentTimeMillis();
            testBufferedWriter(lineNum);
            end = System.currentTimeMillis();
            long timeElapse_BufferedWriter = end - begin;
            bufferedWriter.write(String.valueOf(timeElapse_BufferedWriter)+"\t");
        }
        System.out.println("Test BufferedWriter end.\n");
 
        System.out.println("Test NewOutputStream begin.");
        bufferedWriter.write("\n");
        for (int lineNum = startlineNum; lineNum < maxlineNum; lineNum *= Multiplying) {
            begin = System.currentTimeMillis();
            testNewOutputStream(lineNum);
            end = System.currentTimeMillis();
            long timeElapse_NewOutputStream = end - begin;
            bufferedWriter.write(String.valueOf(timeElapse_NewOutputStream)+"\t");
        }
        System.out.println("Test NewOutputStream end.\n");
 
        System.out.println("Test NewBufferedWriter begin.");
        bufferedWriter.write("\n");
        for (int lineNum = startlineNum; lineNum < maxlineNum; lineNum *= Multiplying) {
            begin = System.currentTimeMillis();
            testNewBufferedWriter(lineNum);
            end = System.currentTimeMillis();
            long timeElapse_NewBufferedWriter = end - begin;
            bufferedWriter.write(String.valueOf(timeElapse_NewBufferedWriter)+"\t");
        }
        System.out.println("Test NewOutputStream end.\n");
 
        bufferedWriter.close();
    }