nio 读写文件

package FSOperation;

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.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;

public class MyMain {

	
	public static void main(String[] args){
		File file = new File("D:/a.txt");
		try {
			FileInputStream fileInput = new FileInputStream(file);
			FileChannel fileInputChannel = fileInput.getChannel();
			ByteBuffer bytebuffer = fileInputChannel.map(MapMode.READ_ONLY, 0, file.length());
			
			FileOutputStream fileOutput =new FileOutputStream("D:/b.txt");
			FileChannel fileOutputChannel = fileOutput.getChannel();
			fileOutputChannel.write(bytebuffer);
			bytebuffer.clear();
			
			fileInputChannel.close();
			fileOutputChannel.close();
			
			System.out.println(System.getProperties());
		} catch (FileNotFoundException e) {

			e.printStackTrace();
			
		} catch(IOException e){
			
		}
		
		
	}
}

运行结果：
将a.txt 里面的内容写到了b.txt 里面