FileInputStream 与 MappedByteBuffer

package read;

import java.io.*;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;

/**
 * Created by joyce on 2019/9/23.
 */
public class FormerReader {
    public static void main(String [] f) throws Exception {

        File fileIn = new File("/Users/joyce/Downloads/java.pdf"); //打开源文件
        File fileOut = new File("/Users/joyce/Downloads/target.pdf");

        // 普通stream方式
        long formerStart = System.currentTimeMillis();
        FileInputStream streamln = new FileInputStream (fileIn);
        FileOutputStream streamOut = new FileOutputStream (fileOut);
        int c;
        while ((c = streamln.read()) != -1) {
            streamOut.write(c);
        }
        streamln.close();
        streamOut.close();
        long formerEnd = System.currentTimeMillis();
        System.out.println((formerStart-formerEnd)/1000);

        // nio MappedByteBuffer
        formerStart = System.currentTimeMillis();
        long len = fileIn.length();
        FileChannel fileChannel = new RandomAccessFile(fileIn, "r").getChannel();
        MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, len);
        MappedByteBuffer mappedByteBufferout = new RandomAccessFile(fileOut, "rw").getChannel().map(FileChannel.MapMode.READ_WRITE, 0, len);

        for (int offset = 0; offset < len; offset++) {
            byte b = mappedByteBuffer.get();
            mappedByteBufferout.put(b);
        }

        formerEnd = System.currentTimeMillis();
        System.out.println((formerStart-formerEnd)/1000);
    }
}

 

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