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SimpleUseOfBuffer.java
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85 lines (74 loc) · 2.61 KB
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package NIO;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
/*
* 使用Buffer的四个步骤：
* （声明buffer，绑定到通道）
* 1.写数据到Buffer
* ---a. int bytesRead=inChannel.read(buf)//read into buf
* ---b. buf.read(123);
* 2.调用buffer.flip()//从写模式切换到度模式
* --- 即将limit=position position=0
* 3.从buffer中读数据
* ---a. int bytesWrite=inChannel.write(buf)//从buf中读数据到channel
* ---b. buf.get()
* 4.调用buffer.clear()或者buffer.compact()
* ---buf.clear():positon=0,limit=capacity “忘记”哪些数据读过，哪些没有
* ---buf.compact():将未读过的数据都放在开头，position=最后一个数据后面
*
* buf.rewind():position=0,limit不变，你可以重读buf中的所有数据
*
* buf.mark():mark=positon:标记position
* buf.reset():position=mark:重新回到之前的position
*
*
*
* 其他几个基本函数：
* buf.equals():比较剩余的值是否相等
* ------ByteBuffer.equals()
* p=postion;
* for(int i=this.limit-1,int j=that.limit-1;i>=p;i--,j--)
* buf.compare():
* ------ByteBuffer.compareTo():
* n=positon+Math.min(this.remain,that.remain)
* //在剩余的值中
* for(i=this.position,j=that.position;i<n;i++)
* //如果谁的值大，谁就大
* int temp=if(compare(this.get(i),that.get(i)))
* if(temp!=0)
* return temp;
* //如果剩余值都相同，谁数据多谁就大
* return this.remain-that.remain;
* */
public class SimpleUseOfBuffer {
public static void main(String[] args){
try {
RandomAccessFile randomFile;
randomFile = new RandomAccessFile("src\\employee.txt", "rw");
FileChannel inChannel= randomFile.getChannel();
ByteBuffer byteBuffer=ByteBuffer.allocate(10);
//从通道中读一组字节序列到缓存中
int bytesRead=inChannel.read(byteBuffer);
while(bytesRead!=-1) {
System.out.println("Read"+bytesRead);
//从buffer中读取数据
byteBuffer.flip();
while(byteBuffer.hasRemaining()) {
System.out.println("buf:"+(char)byteBuffer.get());//从buf中取数据
}
byteBuffer.clear();
bytesRead=inChannel.read(byteBuffer);
}
randomFile.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}