Java:io流写入文件的四种实现方式的效率对比

package chris;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;


public class CopyPdfDemo {
    public static void main(String[] args) throws IOException {
        long start=System.currentTimeMillis();
//      method1("G:\\src.pdf","Mypdf.pdf");
//      method2("G:\\src.pdf.pdf","Mypdf.pdf");
//      method3("G:\\src.pdf.pdf","Mypdf.pdf");
        method4("G:\\src.pdf.pdf","Mypdf.pdf");

        long end=System.currentTimeMillis();
        System.out.println("共耗时"+(end-start)+"毫秒");
    }

    //单字节写入--共耗时196000毫秒
    private static void method1(String srcString, String destString) throws IOException {
        FileInputStream fis=new FileInputStream(srcString);
        FileOutputStream fos=new FileOutputStream(destString);

        int by=0;
        while((by=fis.read())!=-1){
            fos.write(by);
        }

        fos.close();
        fis.close();
    }
    //字节数组写入---共耗时297毫秒
    private static void method2(String srcString, String destString) throws IOException {
        FileInputStream fis=new FileInputStream(srcString);
        FileOutputStream fos=new FileOutputStream(destString);

        byte[] by= new byte[1024];
        int len=0;
        while((len=fis.read(by))!=-1){
            fos.write(by);
        }

        fos.close();
        fis.close();
    }
    //缓冲区单字节写入---共耗时938毫秒
    private static void method3(String srcString, String destString) throws IOException {
        BufferedInputStream bis=new BufferedInputStream(new FileInputStream(srcString));
        BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(destString));

        int by = 0;
        while((by=bis.read())!=-1){
            bos.write(by);
        }

        bos.close();
        bis.close();
    }
    //缓冲区字节数组写入----共耗时63毫秒---最高效
    private static void method4(String srcString, String destString) throws IOException {
        BufferedInputStream bis=new BufferedInputStream(new FileInputStream(srcString));
        BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(destString));

        byte[] by=new byte[1024];
        int len = 0;
        while((len=bis.read(by))!=-1){
            bos.write(by);
        }

        bos.close();
        bis.close();
    }

}