package nioDemo;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
package nioDemo;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.file.Path;
import java.nio.file.Paths;
public class FileChannelDemo {
public static void main(String[] args){
/*创建文件，向文件中写入数据*/
try {
/*如果文件不存在，创建该文件,文件后缀是不是文本文件不重要*/
File file = new File("E:/noi_utf8.data");
if(!file.exists()){
file.createNewFile();
}
/*根据文件输出流创建与这个文件相关的通道*/
FileOutputStream fos = new FileOutputStream(file);
FileChannel fc = fos.getChannel();
/*创建ByteBuffer对象， position = 0, limit = 64*/
ByteBuffer bb = ByteBuffer.allocate(64);
/*向ByteBuffer中放入字符串UTF-8的字节, position = 17, limit = 64*/
bb.put("Hello,World 123 \n".getBytes("UTF-8"));
/*flip方法 position = 0, limit = 17*/
bb.flip();
/*write方法使得ByteBuffer的position到 limit中的元素写入通道中*/
fc.write(bb);
/*clear方法使得position = 0， limit = 64*/
bb.clear();
/*下面的代码同理*/
bb.put("你好，世界 456".getBytes("UTF-8"));
bb.flip();
fc.write(bb);
bb.clear();
fos.close();
fc.close();
} catch (FileNotFoundException e) {
} catch (IOException e) {
System.out.println(e);
}
/*从刚才的文件中读取字符序列*/
try {
/*通过Path对象创建文件通道*/
Path path = Paths.get("E:/noi_utf8.data");
FileChannel fc = FileChannel.open(path);
ByteBuffer bb = ByteBuffer.allocate((int) fc.size()+1);
Charset utf8 = Charset.forName("UTF-8");
/*阻塞模式，读取完成才能返回*/
fc.read(bb);
bb.flip();
CharBuffer cb = utf8.decode(bb);
System.out.print(cb.toString());
bb.clear();
fc.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
2.2 ServerSocketChannel