A Serialized stream is represented by any stream satisfying the stream rule.

stream:
  magic version contents

contents:
  content
  contents content

content:
  object
  blockdata

object:
  newObject
  newClass
  newArray
  newString
  newEnum
  newClassDesc
  prevObject
  nullReference
  exception
  TC_RESET

newClass:
  TC_CLASS classDesc newHandle

classDesc:
  newClassDesc
  nullReference
  (ClassDesc)prevObject      // an object required to be of type
                             // ClassDesc

superClassDesc:
  classDesc

newClassDesc:
  TC_CLASSDESC className serialVersionUID newHandle classDescInfo
  TC_PROXYCLASSDESC newHandle proxyClassDescInfo

classDescInfo:
  classDescFlags fields classAnnotation superClassDesc 

className:
  (utf)

serialVersionUID:
  (long)

classDescFlags:
  (byte)                  // Defined in Terminal Symbols and
                            // Constants

proxyClassDescInfo:
  (int)<count> proxyInterfaceName[count] classAnnotation
      superClassDesc

proxyInterfaceName:

  (utf)

fields:
  (short)<count>  fieldDesc[count]

fieldDesc:
  primitiveDesc
  objectDesc

primitiveDesc:
  prim_typecode fieldName

objectDesc:
  obj_typecode fieldName className1

fieldName:
  (utf)

className1:
  (String)object             // String containing the field's type,
                             // in field descriptor format

classAnnotation:
  endBlockData
  contents endBlockData      // contents written by annotateClass

prim_typecode:
  `B'	// byte
  `C'	// char
  `D'	// double
  `F'	// float
  `I'	// integer
  `J'	// long
  `S'	// short
  `Z'	// boolean

obj_typecode:
  `[`	// array
  `L'	// object

newArray:
  TC_ARRAY classDesc newHandle (int)<size> values[size]

newObject:
  TC_OBJECT classDesc newHandle classdata[]  // data for each class

classdata:
  nowrclass                 // SC_SERIALIZABLE & classDescFlag &&
                            // !(SC_WRITE_METHOD & classDescFlags)
  wrclass objectAnnotation  // SC_SERIALIZABLE & classDescFlag &&
                            // SC_WRITE_METHOD & classDescFlags
  externalContents          // SC_EXTERNALIZABLE & classDescFlag &&
                            // !(SC_BLOCKDATA  & classDescFlags
  objectAnnotation          // SC_EXTERNALIZABLE & classDescFlag&& 
                            // SC_BLOCKDATA & classDescFlags

nowrclass:
  values                    // fields in order of class descriptor

wrclass:
  nowrclass

objectAnnotation:
  endBlockData
  contents endBlockData     // contents written by writeObject
                            // or writeExternal PROTOCOL_VERSION_2.

blockdata:
  blockdatashort
  blockdatalong

blockdatashort:
  TC_BLOCKDATA (unsigned byte)<size> (byte)[size]

blockdatalong:
  TC_BLOCKDATALONG (int)<size> (byte)[size]

endBlockData	:
  TC_ENDBLOCKDATA

externalContent:          // Only parseable by readExternal
  ( bytes)                // primitive data
    object

externalContents:         // externalContent written by 
  externalContent         // writeExternal in PROTOCOL_VERSION_1.
  externalContents externalContent

newString:
  TC_STRING newHandle (utf)
  TC_LONGSTRING newHandle (long-utf)

newEnum:
  TC_ENUM classDesc newHandle enumConstantName

enumConstantName:
  (String)object

prevObject
  TC_REFERENCE (int)handle

nullReference
  TC_NULL

exception:
  TC_EXCEPTION reset (Throwable)object	 reset 

magic:
  STREAM_MAGIC

version
  STREAM_VERSION

values:          // The size and types are described by the
                 // classDesc for the current object

newHandle:       // The next number in sequence is assigned
                 // to the object being serialized or deserialized

reset:           // The set of known objects is discarded
                 // so the objects of the exception do not
                 // overlap with the previously sent objects 
                 // or with objects that may be sent after 
                 // the exception

The following symbols in java.io.ObjectStreamConstants define the terminal and constant values expected in a stream.

    final static short STREAM_MAGIC = (short)0xaced;
    final static short STREAM_VERSION = 5;
    final static byte TC_NULL = (byte)0x70;
    final static byte TC_REFERENCE = (byte)0x71;
    final static byte TC_CLASSDESC = (byte)0x72;
    final static byte TC_OBJECT = (byte)0x73;
    final static byte TC_STRING = (byte)0x74;
    final static byte TC_ARRAY = (byte)0x75;
    final static byte TC_CLASS = (byte)0x76;
    final static byte TC_BLOCKDATA = (byte)0x77;
    final static byte TC_ENDBLOCKDATA = (byte)0x78;
    final static byte TC_RESET = (byte)0x79;
    final static byte TC_BLOCKDATALONG = (byte)0x7A;
    final static byte TC_EXCEPTION = (byte)0x7B;
    final static byte TC_LONGSTRING = (byte) 0x7C;
    final static byte TC_PROXYCLASSDESC = (byte) 0x7D;
    final static byte TC_ENUM = (byte) 0x7E;
    final static  int   baseWireHandle = 0x7E0000;

The flag byte classDescFlags may include values of

    final static byte SC_WRITE_METHOD = 0x01; //if SC_SERIALIZABLE
     final static byte SC_BLOCK_DATA = 0x08;    //if SC_EXTERNALIZABLE
    final static byte SC_SERIALIZABLE = 0x02;
    final static byte SC_EXTERNALIZABLE = 0x04;
    final static byte SC_ENUM = 0x10;

The flag SC_WRITE_METHOD is set if the Serializable class writing the stream had a writeObject method that may have written additional data to the stream. In this case a TC_ENDBLOCKDATA marker is always expected to terminate the data for that class.

The flag SC_BLOCKDATA is set if the Externalizable class is written into the stream using STREAM_PROTOCOL_2. By default, this is the protocol used to write Externalizable objects into the stream in JDK^TM 1.2. JDK^TM 1.1 writes STREAM_PROTOCOL_1.

The flag SC_SERIALIZABLE is set if the class that wrote the stream extended java.io.Serializable but not java.io.Externalizable, the class reading the stream must also extend java.io.Serializable and the default serialization mechanism is to be used.

The flag SC_EXTERNALIZABLE is set if the class that wrote the stream extended java.io.Externalizable, the class reading the data must also extend Externalizable and the data will be read using its writeExternal and readExternal methods.

The flag SC_ENUM is set if the class that wrote the stream was an enum type. The receiver's corresponding class must also be an enum type. Data for constants of the enum type will be written and read as described in Section 1.12, "Serialization of Enum Constants".