java NIO方式进行读写文件和内容

java NIO方式进行读写文件和内容

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

/**
 * 
 * 测试JAVA NIO方式读取文件，写出内容到文件
 *
 */
public class NIOTest {

	
	public static void main(String[] args) {
		readNIO();
	}
		/**
		 * 最终确认，是因为UTF-8编码的时候，是变长的（可能1-4个字节），所以在
		 * ByteBuffer bf = ByteBuffer.allocate(capacity);
		 * byte[] bytes = bf.array();
		 * 的时候，会出现数字英文和中文边界截断了的问题，所以导致出现测���java 文件操作这样的乱码。
		 * 解决方案1：对这类文件不进行截断输出，整个输出
		 * 解决方案2：截断输出的时候，判断编码边界。进行减长度操作，避免截断了中文。
		 */
	
	 public static void readNIO() {
	        FileInputStream fin = null;
	        try {
	            fin = new FileInputStream(new File("D:\\add0.txt"));
	            FileChannel channel = fin.getChannel();

	            int capacity = 1024;// 字节
	            ByteBuffer bf = ByteBuffer.allocate(capacity);
	            System.out.println("限制是：" + bf.limit() + ",容量是：" + bf.capacity() + " ,位置是：" + bf.position());
	            int length = -1;
	           
	            while ((length = channel.read(bf)) != -1) {

	                /*
	                 * 注意，读取后，将位置置为0，将limit置为容量, 以备下次读入到字节缓冲中，从0开始存储
	                 */
	                bf.clear();
	                byte[] bytes = bf.array();
	                //System.out.println("start..............");
	                最后输出就会有乱码符号：测���java 文件操作这样输出也有乱码
	                String str = new String(bytes, 0, length,"UTF-8");
	                System.out.println(str);
	                //System.out.write(bytes, 0, length);

	                //System.out.println("end................");

	               System.out.println("限制是：" + bf.limit() + "容量是：" + bf.capacity() + "位置是：" + bf.position());

	            }
	            //最后输出就会有乱码符号：测���java 文件操作
	            //System.out.println(str);
	            channel.close();

	        } catch (FileNotFoundException e) {
	            e.printStackTrace();
	        } catch (IOException e) {
	            e.printStackTrace();
	        } finally {
	            if (fin != null) {
	                try {
	                    fin.close();
	                } catch (IOException e) {
	                    e.printStackTrace();
	                }
	            }
	        }
	    }

	 
	
	/**通道之间的数据传输(直接缓冲区的模式)
	 * 耗费时间:68
    *
    */
   private static void   nioCopyTest3() throws IOException {
       long startTime = System.currentTimeMillis();

       FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);

       FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 13.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);

       outChennel.transferFrom(inChannel,0,inChannel.size());

       long end = System.currentTimeMillis();
       System.out.println("nioCopyTest3耗费时间:"+(end-startTime));
   }

   /**
    * 使用直接缓冲区完成文件的复制(内存映射文件)
    * 耗费时间:142
    */
   private static void  nioCopyTest2() throws IOException {
       long startTime = System.currentTimeMillis();

       FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);

       FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 12.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);

       //内存映射文件(什么模式 从哪开始 到哪结束)
       MappedByteBuffer inMappeBuf = inChannel.map(FileChannel.MapMode.READ_ONLY,0,inChannel.size());
       MappedByteBuffer outMappeBuf =  outChennel.map(FileChannel.MapMode.READ_WRITE,0,inChannel.size());

       //直接都缓冲区进行数据的读写操作
       byte[] dst = new byte[inMappeBuf.limit()];
       inMappeBuf.get(dst);
       outMappeBuf.put(dst);

       inChannel.close();
       outChennel.close();
       long end = System.currentTimeMillis();
       System.out.println("nioCopyTest2耗费时间:"+(end-startTime));
   }


   /**
    *  非直接缓冲区 文件的复制
    *  耗费时间:1417
    * @throws IOException
    */
   private static void nioCopyTest1()throws IOException {
       long startTime = System.currentTimeMillis();
       FileInputStream fileInputStream = new FileInputStream(new File("E:\\ 1.avi"));
       FileOutputStream fileOutputStream = new FileOutputStream("E:\\ 11.avi");

       //获取通道
       FileChannel inChannel = fileInputStream.getChannel();
       FileChannel outChanel = fileOutputStream.getChannel();

       //分配缓冲区的大小
       ByteBuffer buf = ByteBuffer.allocate(1024);

       //将通道中的数据存入缓冲区
       while (inChannel.read(buf) != -1) {
           buf.flip();//切换读取数据的模式
           outChanel.write(buf);
           buf.clear();
       }
       outChanel.close();
       inChannel.close();
       fileInputStream.close();
       fileOutputStream.close();
       long end = System.currentTimeMillis();
       System.out.println("nioCopyTest1耗费时间:"+(end-startTime));
   }
}