[Java]IO(Input/Output)Stream,Reader,File System

1. Package
   The package for IO and FS operation is java.io.
   
2. Access File System
   
   • File
     Use the class File to access file system, such as rename, delete, listFile, etc.
     
   • xxx
     
3. Input
   Get input from any source of data that can send out a sequence of bytes, such as file, network, memory etc.
   
   • InputStream
     
   • FileInputStream
   • StringInputStream
     Read data from a string object.
     
   • DataInputStream
     Read the specified length of data,
     Read boolean, long, float, int, short, byte, UTF, xxx
     Read a line,
   • RandomAccessFile
     Allows reading from and writing to a file in a random-access manner. If the file is opened in read/write mode, write operations are available as well. The position of the next read or write operation can be moved forwards and backwards after every operation.
4. Output
   Send output to any destination that can receive a sequence of bytes.
   
   • OutputStream
     
   • FileOutputStream
   • StringOutputStream
     Write data to a string object.
     
   • DataOutputStream
     Write the specified length of data,
     Write boolean, long, float, int, short, byte, UTF, xxx
     
5. ParcelFileDescriptor & AssetFileDescriptor
   
   • ParcelFileDescriptor
     ParcelFileDescriptor is created from File/Socket object, and it implements Parcel that can be transfered between different components/applications
     
   • AssetFileDescriptor
     Create FileInputStream/FileOutputStream object with ParcelFileDescriptor object,
     
   • xxx
     
6. I/O Diagram
   
   
   Another diagram
   
   
   
   
   
   
   
7. File System
   
   
   
   
8. Serialization
   串行化（Serialization）：把对象的表示转换成字节流的表示。
   反串行化（Deserialization）：从字节流中把对象的重建出来。
   
   自定义串行化、反串行化类:
   实现Serializable中的方法：
   private void writeObject(java.io.ObjectOutputStream out) throws IOException
   private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException
   
   
   public final class SavingsAccount implements Serializable
   {
       private long mId;
       private name = mName;   
       private mX, mY, mW, mH;
      
       ObjectStreamField[] mFields =
       {
        new ObjectStreamField(“x”, Double.TYPE),
           new ObjectStreamField(“y”, Double.TYPE),
           new ObjectStreamField(“w”, Double.TYPE),
           new ObjectStreamField(“h”, Double.TYPE),
       };
   
       private void readObject( ObjectInputStream aInputStream) throws ClassNotFoundException, IOException
       {
           mId = aInputStream.readLong();
        mName = aInputStream.readUTF();
   
           ObjectInputStream.GetField fields = aInputStream.readFields();
           mX = fields.get(“x”, 0.0);
           mY =  fields.get(“y”, 0.0);
           mW =  fields.get(“w”, 0.0);
           mH =  fields.get(“h”, 0.0);
       }
   
       private void writeObject(ObjectOutputStream aOutputStream) throws IOException
       {
           aInputStream.writeLong(mId);
           aInputStream.writeUTF(mName);
   
           ObjectOutputStream .GetField fields = aOutputStream.putFields();
           mX = fields.put(“x”, 0.0);
           mY =  fields.put(“y”, 0.0);
           mW =  fields.put(“w”, 0.0);
           mH =  fields.put(“h”, 0.0);
           fields.writeFields();
       }
   }
   
9. StringTokenizer
   Allow an application to break a string into tokens by performing code point comparison.
   
10. xxx