publicabstractclassByteBufferextendsBufferimplementsComparable<ByteBuffer>{
// These fields are declared here rather than in Heap-X-Buffer in order to// reduce the number of virtual method invocations needed to access these// values, which is especially costly when coding small buffers.////存储数据的byte数组finalbyte[] hb;                  // Non-null only for heap buffersfinalintoffset;
booleanisReadOnly;                 // Valid only for heap buffers

publicabstractclassBuffer {
//返回此缓冲区容量capacitypublicfinalintcapacity( )
//返回此缓冲区位置positionpublicfinalintposition( )
//设置缓冲区的位置position publicfinalBufferposition (intnewPositio)
//返回此缓冲区limitpublicfinalintlimit( )
//设置此缓冲区的限制limitpublicfinalBufferlimit (intnewLimit)
//在此缓冲区的位置设置标记publicfinalBuffermark( )
//将此缓冲区的位置重置为以前标记的位置//把position设置为markpublicfinalBufferreset()
//清除此缓冲区, 即将各个标记恢复到初始状态//把position设置为 0 ，limit = capacity;publicfinalBufferclear( )
//读写反转此缓冲区publicfinalBufferflip( )
//重置此缓冲区，position = 0;   mark = -1;publicfinalBufferrewind( )
//返回当前位置与限制之间的元素数publicfinalintremaining( )
//返回当前位置之后是否还有元素publicfinalbooleanhasRemaining( )
//告知此缓冲区是否为只读缓冲区publicabstractbooleanisReadOnly( );
//返回此缓冲区是否具有可访问的底层实现数组publicabstractbooleanhasArray();
//返回此缓冲区的底层实现数组publicabstractObjectarray();
//返回此缓冲区的底层实现数组中第一个缓冲区元素的偏移量publicabstractintarrayOffset();
//告知此缓冲区是否为直接缓冲区publicabstractbooleanisDirect();
}
publicabstractclassFileChannelextendsAbstractInterruptibleChannelimplementsSeekableByteChannel, GatheringByteChannel, ScatteringByteChannel{
//从通道读取数据并放到缓冲区中publicintread(ByteBufferdst) ;
//把缓冲区的数据写到通道中publicintwrite(ByteBuffersrc) ;
//从目标通道中复制数据到当前通道publiclongtransferFrom(ReadableByteChannelsrc, longposition, longcount);
//把数据从当前通道复制给目标通道publiclongtransferTo(longposition, longcount, WritableByteChanneltarget);
}

@TestpublicvoidbyteBufferTest(){
//创建一个容量 1024 的bytebufferByteBufferbyteBuffer=ByteBuffer.allocate(1024);
//存储元素byteBuffer.putChar('哈');
byteBuffer.putInt(123);
byteBuffer.putShort((short) 123);
//读写转换byteBuffer.flip();
//获取元素System.out.println(byteBuffer.getChar());   //哈System.out.println(byteBuffer.getInt());    //123System.out.println(byteBuffer.getLong());   //BufferUnderflowException 缓冲区溢出异常}

//使用NIO向磁盘写一个文件@TestpublicvoidnioWriteTest() throwsIOException {
//文件输出流FileOutputStreamfileOutputStream=newFileOutputStream("d:/1.txt");
//获取通道FileChannelchannel=fileOutputStream.getChannel();
//构建一个 容量1024字节长度的缓冲取ByteBufferbyteBuffer=ByteBuffer.allocate(1024);
System.out.println(byteBuffer.getClass().getName());
//给buffer写入数据byteBuffer.put("你好NIO".getBytes());
//转换byteBuffer.flip();
//把buffer中的数据通过通道写入初盘文件channel.write(byteBuffer);
//关闭通道channel.close();
//关闭输出流fileOutputStream.close();
   }

@TestpublicvoidnioReadTest() throwsIOException {
//文件输入流Filefile=newFile("d:/1.txt");
FileInputStreamfileInputStream=newFileInputStream(file);
//获取通道FileChannelchannel=fileInputStream.getChannel();
//创建一个buffer,容量为file的长度ByteBufferbyteBuffer=ByteBuffer.allocate((int)file.length());
//从通道中读取数据到bytebuffer中channel.read(byteBuffer);
//输出结果System.out.println(newString(byteBuffer.array()));
//关闭资源channel.close();
fileInputStream.close();
 }

//文件拷贝 1.txt 中的内容拷贝到2.txt@TestpublicvoidnioCopyTest() throwsIOException {
//文件对象Filefile=newFile("d:/1.txt");
//文件输入流FileInputStreamfileInputStream=newFileInputStream(file);
//得到通道FileChannelchannel=fileInputStream.getChannel();
//文件输出流FileOutputStreamfileOutputStream=newFileOutputStream("d:/2.txt");
//获取通道FileChanneloutChannel=fileOutputStream.getChannel();
//缓冲区，容量为file的长度ByteBufferbyteBuffer=ByteBuffer.allocate((int)file.length());
while(true){
//每次读取需要把缓冲区复位,否则当bytebuffer总的position等于limit的时候，//read的返回值是 0 ，用于不会走-1，就会死循环byteBuffer.clear();
//把数据读取到缓冲区intreadLenth=channel.read(byteBuffer);
System.out.println("redLength = "+readLenth);
//读取结果长度为-1说明读完了if(readLenth==-1){
break;
        }
//缓冲区读写交换byteBuffer.flip();
outChannel.write(byteBuffer);
    }
//关闭通道channel.close();
//关闭流fileInputStream.close();
//关闭通道outChannel.close();
//关闭流fileOutputStream.close();
}

publicabstractlongtransferFrom(ReadableByteChannelsrc,
longposition, longcount)throwsIOException;

//文件拷贝 1.txt 中的内容拷贝到2.txt@TestpublicvoidnioCopyTest2() throwsIOException {
//读操作=================================================================================//文件对象Filefile=newFile("d:/1.txt");
//文件输入流FileInputStreamfileInputStream=newFileInputStream(file);
//得到通道FileChannelinputChannel=fileInputStream.getChannel();
//文件输出流FileOutputStreamfileOutputStream=newFileOutputStream("d:/2.txt");
//获取通道FileChanneloutChannel=fileOutputStream.getChannel();
//使用transferFrom拷贝数据，将inputChannel中数据拷贝到outChanneloutChannel.transferFrom(inputChannel, 0, inputChannel.size());
outChannel.close();
inputChannel.close();
fileInputStream.close();
fileOutputStream.close();
  }

/*** 只读buffer*/@TestpublicvoidnioOnlyRead() throwsIOException {
ByteBufferbyteBuffer=ByteBuffer.allocate(1024);
for (inti=0 ; i<10 ; i++){
byteBuffer.putInt(i);   //0123456789    }
//读写转换byteBuffer.flip();
//得到一个只读buffer ,使用的是java.nio.HeapByteBufferRByteBufferreadOnlyBuffer=byteBuffer.asReadOnlyBuffer();
//java.nio.HeapByteBufferRSystem.out.println(readOnlyBuffer.getClass().getName());
while(readOnlyBuffer.hasRemaining()){
System.out.print(readOnlyBuffer.getInt());  //0123456789    }
readOnlyBuffer.putInt(10);  //ReadOnlyBufferException ,不允许写}

@TestpublicvoidmappedByteBuffer() throwsIOException {
//随机访问文件，RW代表支持而读写,文件内容为 ：helloworldFilefile=newFile("d:/3.txt");
RandomAccessFilerandomAccessFile=newRandomAccessFile(file,"rw");
//通道FileChannelchannel=randomAccessFile.getChannel();
//得到MappedByteBuffer ： mode：读写模式， position: 映射区域的起始位置 size: 映射区域大小MappedByteBuffermappedByteBuffer=channel.map(FileChannel.MapMode.READ_WRITE, 0, file.length());
//第1个字节修改为 大 HmappedByteBuffer.put(0,(byte)'H');
//第6个字节修改为 大 WmappedByteBuffer.put(5,(byte)'W');
randomAccessFile.close();
 }