# ObjectOutputStream

public class **ObjectOutputStream** extends [OutputStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html)  
implements [ObjectOutput](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html) [ObjectStreamConstants](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html) An ObjectOutputStream writes primitive data types and graphs of Java objects
to an OutputStream. The objects can be read (reconstituted) using an
ObjectInputStream. Persistent storage of objects can be accomplished by
using a file for the stream. If the stream is a network socket stream, the
objects can be reconstituted on another host or in another process.

Only objects that support the java.io.Serializable interface can be
written to streams. The class of each serializable object is encoded
including the class name and signature of the class, the values of the
object's fields and arrays, and the closure of any other objects referenced
from the initial objects.

The method writeObject is used to write an object to the stream. Any
object, including Strings and arrays, is written with writeObject. Multiple
objects or primitives can be written to the stream. The objects must be
read back from the corresponding ObjectInputstream with the same types and
in the same order as they were written.

Primitive data types can also be written to the stream using the
appropriate methods from DataOutput. Strings can also be written using the
writeUTF method.

The default serialization mechanism for an object writes the class of the
object, the class signature, and the values of all non-transient and
non-static fields. References to other objects (except in transient or
static fields) cause those objects to be written also. Multiple references
to a single object are encoded using a reference sharing mechanism so that
graphs of objects can be restored to the same shape as when the original was
written.

For example to write an object that can be read by the example in
ObjectInputStream:


```
      FileOutputStream fos = new FileOutputStream("t.tmp");
      ObjectOutputStream oos = new ObjectOutputStream(fos);

      oos.writeInt(12345);
      oos.writeObject("Today");
      oos.writeObject(new Date());

      oos.close();
 
```

Classes that require special handling during the serialization and
deserialization process must implement special methods with these exact
signatures:


```
 private void readObject(java.io.ObjectInputStream stream)
     throws IOException, ClassNotFoundException;
 private void writeObject(java.io.ObjectOutputStream stream)
     throws IOException
 private void readObjectNoData()
     throws ObjectStreamException;
 
```

The writeObject method is responsible for writing the state of the object
for its particular class so that the corresponding readObject method can
restore it. The method does not need to concern itself with the state
belonging to the object's superclasses or subclasses. State is saved by
writing the individual fields to the ObjectOutputStream using the
writeObject method or by using the methods for primitive data types
supported by DataOutput.

Serialization does not write out the fields of any object that does not
implement the java.io.Serializable interface. Subclasses of Objects that
are not serializable can be serializable. In this case the non-serializable
class must have a no-arg constructor to allow its fields to be initialized.
In this case it is the responsibility of the subclass to save and restore
the state of the non-serializable class. It is frequently the case that the
fields of that class are accessible (public, package, or protected) or that
there are get and set methods that can be used to restore the state.

Serialization of an object can be prevented by implementing writeObject
and readObject methods that throw the NotSerializableException. The
exception will be caught by the ObjectOutputStream and abort the
serialization process.

Implementing the Externalizable interface allows the object to assume
complete control over the contents and format of the object's serialized
form. The methods of the Externalizable interface, writeExternal and
readExternal, are called to save and restore the objects state. When
implemented by a class they can write and read their own state using all of
the methods of ObjectOutput and ObjectInput. It is the responsibility of
the objects to handle any versioning that occurs.

Enum constants are serialized differently than ordinary serializable or
externalizable objects. The serialized form of an enum constant consists
solely of its name; field values of the constant are not transmitted. To
serialize an enum constant, ObjectOutputStream writes the string returned by
the constant's name method. Like other serializable or externalizable
objects, enum constants can function as the targets of back references
appearing subsequently in the serialization stream. The process by which
enum constants are serialized cannot be customized; any class-specific
writeObject and writeReplace methods defined by enum types are ignored
during serialization. Similarly, any serialPersistentFields or
serialVersionUID field declarations are also ignored--all enum types have a
fixed serialVersionUID of 0L.

Primitive data, excluding serializable fields and externalizable data, is
written to the ObjectOutputStream in block-data records. A block data record
is composed of a header and data. The block data header consists of a marker
and the number of bytes to follow the header. Consecutive primitive data
writes are merged into one block-data record. The blocking factor used for
a block-data record will be 1024 bytes. Each block-data record will be
filled up to 1024 bytes, or be written whenever there is a termination of
block-data mode. Calls to the ObjectOutputStream methods writeObject,
defaultWriteObject and writeFields initially terminate any existing
block-data record.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectInputStream.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Serializable.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Externalizable.html`
- [Object Serialization Specification, Section 2, Object Output Classes](https://developers.google.com/j2objc/javadoc/jre/platform/serialization/spec/output.html)

### Nested Class Summary

|---|---|---|---|
| class | [ObjectOutputStream.PutField](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.PutField.html) || Provide programmatic access to the persistent fields to be written to ObjectOutput. |

### Inherited Constant Summary

From interface [java.io.ObjectStreamConstants](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html)

|---|---|---|
| int | [PROTOCOL_VERSION_1](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#PROTOCOL_VERSION_1) | Stream protocol version 1. |
| int | [PROTOCOL_VERSION_2](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#PROTOCOL_VERSION_2) | Stream protocol version 2. |
| byte | [SC_BLOCK_DATA](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SC_BLOCK_DATA) | Bit mask for the `flag` field in ObjectStreamClass. |
| byte | [SC_ENUM](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SC_ENUM) | Bit mask for the `flag` field in ObjectStreamClass. |
| byte | [SC_EXTERNALIZABLE](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SC_EXTERNALIZABLE) | Bit mask for the `flag` field in ObjectStreamClass. |
| byte | [SC_SERIALIZABLE](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SC_SERIALIZABLE) | Bit mask for the `flag` field in ObjectStreamClass. |
| byte | [SC_WRITE_METHOD](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SC_WRITE_METHOD) | Bit mask for the `flag` field in ObjectStreamClass. |
| short | [STREAM_MAGIC](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#STREAM_MAGIC) | The stream header's magic number. |
| short | [STREAM_VERSION](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#STREAM_VERSION) | The stream header's version number. |
| byte | [TC_ARRAY](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_ARRAY) | Tag to mark a new array. |
| byte | [TC_BASE](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_BASE) | The minimum tag value. |
| byte | [TC_BLOCKDATA](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_BLOCKDATA) | Tag to mark a block of optional data. |
| byte | [TC_BLOCKDATALONG](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_BLOCKDATALONG) | Tag to mark a long block of data. |
| byte | [TC_CLASS](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_CLASS) | Tag to mark a reference to a class. |
| byte | [TC_CLASSDESC](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_CLASSDESC) | Tag to mark a new class descriptor. |
| byte | [TC_ENDBLOCKDATA](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_ENDBLOCKDATA) | Tag to mark the end of block data blocks for an object. |
| byte | [TC_ENUM](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_ENUM) | Tag to mark a new enum. |
| byte | [TC_EXCEPTION](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_EXCEPTION) | Tag to mark an exception. |
| byte | [TC_LONGSTRING](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_LONGSTRING) | Tag to mark a long string. |
| byte | [TC_MAX](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_MAX) | The maximum tag value. |
| byte | [TC_NULL](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_NULL) | Tag to mark a `null` object reference. |
| byte | [TC_OBJECT](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_OBJECT) | Tag to mark a new object. |
| byte | [TC_PROXYCLASSDESC](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_PROXYCLASSDESC) | Tag to mark a new proxy class descriptor. |
| byte | [TC_REFERENCE](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_REFERENCE) | Tag to mark a reference to an object that has already been written to the stream. |
| byte | [TC_RESET](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_RESET) | Tag to mark a stream reset. |
| byte | [TC_STRING](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#TC_STRING) | Tag to mark a new string. |
| int | [baseWireHandle](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#baseWireHandle) | Handle for the first object that gets serialized. |

### Inherited Field Summary

From interface [java.io.ObjectStreamConstants](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html)

|---|---|---|
| public static final [SerializablePermission](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/SerializablePermission.html) | [SUBCLASS_IMPLEMENTATION_PERMISSION](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SUBCLASS_IMPLEMENTATION_PERMISSION) | Permission constant to enable subclassing of ObjectInputStream and ObjectOutputStream. |
| public static final [SerializablePermission](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/SerializablePermission.html) | [SUBSTITUTION_PERMISSION](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#SUBSTITUTION_PERMISSION) | Permission constant to enable object substitution during serialization and deserialization. |

### Public Constructor Summary

|---|---|
|   | [ObjectOutputStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#ObjectOutputStream(java.io.OutputStream))([OutputStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html) out) Creates an ObjectOutputStream that writes to the specified OutputStream. |

### Protected Constructor Summary

|---|---|
|   | [ObjectOutputStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#ObjectOutputStream())() Provide a way for subclasses that are completely reimplementing ObjectOutputStream to not have to allocate private data just used by this implementation of ObjectOutputStream. |

### Public Method Summary

|---|---|
| void | [close](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#close())() Closes the stream. |
| void | [defaultWriteObject](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#defaultWriteObject())() Write the non-static and non-transient fields of the current class to this stream. |
| void | [flush](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#flush())() Flushes the stream. |
| [ObjectOutputStream.PutField](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.PutField.html) | [putFields](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#putFields())() Retrieve the object used to buffer persistent fields to be written to the stream. |
| void | [reset](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#reset())() Reset will disregard the state of any objects already written to the stream. |
| void | [useProtocolVersion](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#useProtocolVersion(int))(int version) Specify stream protocol version to use when writing the stream. |
| void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#write(byte[]))(byte\[\] buf) Writes an array of bytes. |
| void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#write(byte[],%20int,%20int))(byte\[\] buf, int off, int len) Writes a sub array of bytes. |
| void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#write(int))(int val) Writes a byte. |
| void | [writeBoolean](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeBoolean(boolean))(boolean val) Writes a boolean. |
| void | [writeByte](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeByte(int))(int val) Writes an 8 bit byte. |
| void | [writeBytes](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeBytes(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) str) Writes a String as a sequence of bytes. |
| void | [writeChar](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeChar(int))(int val) Writes a 16 bit char. |
| void | [writeChars](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeChars(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) str) Writes a String as a sequence of chars. |
| void | [writeDouble](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeDouble(double))(double val) Writes a 64 bit double. |
| void | [writeFields](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeFields())() Write the buffered fields to the stream. |
| void | [writeFloat](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeFloat(float))(float val) Writes a 32 bit float. |
| void | [writeInt](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeInt(int))(int val) Writes a 32 bit int. |
| void | [writeLong](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeLong(long))(long val) Writes a 64 bit long. |
| final void | [writeObject](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeObject(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Write the specified object to the ObjectOutputStream. |
| void | [writeShort](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeShort(int))(int val) Writes a 16 bit short. |
| void | [writeUTF](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeUTF(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) str) Primitive data write of this String in [modified UTF-8](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataInput#modified-utf-8) format. |
| void | [writeUnshared](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeUnshared(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Writes an "unshared" object to the ObjectOutputStream. |

### Protected Method Summary

|---|---|
| void | [annotateClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#annotateClass(java.lang.Class<?>))([Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> cl) Subclasses may implement this method to allow class data to be stored in the stream. |
| void | [annotateProxyClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#annotateProxyClass(java.lang.Class<?>))([Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> cl) Subclasses may implement this method to store custom data in the stream along with descriptors for dynamic proxy classes. |
| void | [drain](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#drain())() Drain any buffered data in ObjectOutputStream. |
| boolean | [enableReplaceObject](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#enableReplaceObject(boolean))(boolean enable) Enable the stream to do replacement of objects in the stream. |
| [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) | [replaceObject](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#replaceObject(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) This method will allow trusted subclasses of ObjectOutputStream to substitute one object for another during serialization. |
| void | [writeClassDescriptor](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeClassDescriptor(java.io.ObjectStreamClass))([ObjectStreamClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamClass.html) desc) Write the specified class descriptor to the ObjectOutputStream. |
| void | [writeObjectOverride](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeObjectOverride(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Method used by subclasses to override the default writeObject method. |
| void | [writeStreamHeader](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeStreamHeader())() The writeStreamHeader method is provided so subclasses can append or prepend their own header to the stream. |

### Inherited Method Summary

From class [java.io.OutputStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html)

|---|---|
| void | [close](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html#close())() Closes this output stream and releases any system resources associated with this stream. |
| void | [flush](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html#flush())() Flushes this output stream and forces any buffered output bytes to be written out. |
| void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html#write(byte[]))(byte\[\] b) Writes `b.length` bytes from the specified byte array to this output stream. |
| void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html#write(byte[],%20int,%20int))(byte\[\] b, int off, int len) Writes `len` bytes from the specified byte array starting at offset `off` to this output stream. |
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html#write(int))(int b) Writes the specified byte to this output stream. |

From class [java.lang.Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)

|---|---|
| [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) | [clone](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#clone())() Creates and returns a copy of this `Object`. |
| boolean | [equals](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#equals(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Compares this instance with the specified object and indicates if they are equal. |
| void | [finalize](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#finalize())() Invoked when the garbage collector has detected that this instance is no longer reachable. |
| final [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> | [getClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#getClass())() Returns the unique instance of `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html` that represents this object's class. |
| int | [hashCode](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#hashCode())() Returns an integer hash code for this object. |
| final void | [notify](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notify())() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| final void | [notifyAll](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notifyAll())() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [toString](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#toString())() Returns a string containing a concise, human-readable description of this object. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long,%20int))(long timeout, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long))(long timeout) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait())() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object. |

From interface [java.io.Closeable](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Closeable.html)

|---|---|
| abstract void | [close](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Closeable.html#close())() Closes this stream and releases any system resources associated with it. |

From interface [java.io.Flushable](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Flushable.html)

|---|---|
| abstract void | [flush](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Flushable.html#flush())() Flushes this stream by writing any buffered output to the underlying stream. |

From interface [java.io.ObjectOutput](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html)

|---|---|
| abstract void | [close](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html#close())() Closes the target stream. |
| abstract void | [flush](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html#flush())() Flushes the target stream. |
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html#write(byte[]))(byte\[\] buffer) Writes the entire contents of the byte array `buffer` to the output stream. |
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html#write(byte[],%20int,%20int))(byte\[\] buffer, int offset, int count) Writes `count` bytes from the byte array `buffer` starting at position `offset` to the target stream. |
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html#write(int))(int value) Writes a single byte to the target stream. |
| abstract void | [writeObject](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutput.html#writeObject(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Writes the specified object `obj` to the target stream. |

From interface [java.lang.AutoCloseable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/AutoCloseable.html)

|---|---|
| abstract void | [close](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/AutoCloseable.html#close())() Closes this resource, relinquishing any underlying resources. |

From interface [java.io.DataOutput](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html)

|---|---|
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#write(byte[]))(byte\[\] b) Writes to the output stream all the bytes in array `b`. |
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#write(byte[],%20int,%20int))(byte\[\] b, int off, int len) Writes `len` bytes from array `b`, in order, to the output stream. |
| abstract void | [write](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#write(int))(int b) Writes to the output stream the eight low-order bits of the argument `b`. |
| abstract void | [writeBoolean](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeBoolean(boolean))(boolean v) Writes a `boolean` value to this output stream. |
| abstract void | [writeByte](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeByte(int))(int v) Writes to the output stream the eight low- order bits of the argument `v`. |
| abstract void | [writeBytes](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeBytes(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) s) Writes a string to the output stream. |
| abstract void | [writeChar](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeChar(int))(int v) Writes a `char` value, which is comprised of two bytes, to the output stream. |
| abstract void | [writeChars](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeChars(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) s) Writes every character in the string `s`, to the output stream, in order, two bytes per character. |
| abstract void | [writeDouble](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeDouble(double))(double v) Writes a `double` value, which is comprised of eight bytes, to the output stream. |
| abstract void | [writeFloat](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeFloat(float))(float v) Writes a `float` value, which is comprised of four bytes, to the output stream. |
| abstract void | [writeInt](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeInt(int))(int v) Writes an `int` value, which is comprised of four bytes, to the output stream. |
| abstract void | [writeLong](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeLong(long))(long v) Writes a `long` value, which is comprised of eight bytes, to the output stream. |
| abstract void | [writeShort](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeShort(int))(int v) Writes two bytes to the output stream to represent the value of the argument. |
| abstract void | [writeUTF](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataOutput.html#writeUTF(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) s) Writes two bytes of length information to the output stream, followed by the [modified UTF-8](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataInput#modified-utf-8) representation of every character in the string `s`. |

## Public Constructors

#### public
**ObjectOutputStream**
([OutputStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/OutputStream.html) out)

Creates an ObjectOutputStream that writes to the specified OutputStream.
This constructor writes the serialization stream header to the
underlying stream; callers may wish to flush the stream immediately to
ensure that constructors for receiving ObjectInputStreams will not block
when reading the header.

If a security manager is installed, this constructor will check for
the "enableSubclassImplementation" SerializablePermission when invoked
directly or indirectly by the constructor of a subclass which overrides
the ObjectOutputStream.putFields or ObjectOutputStream.writeUnshared
methods.

##### Parameters

| out | output stream to write to |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if an I/O error occurs while writing stream header |
| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if untrusted subclass illegally overrides security-sensitive methods |
| [NullPointerException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/NullPointerException.html) | if `out` is `null` |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#ObjectOutputStream()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#putFields()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectInputStream.html#ObjectInputStream(java.io.InputStream)`

## Protected Constructors

#### protected
**ObjectOutputStream**
()

Provide a way for subclasses that are completely reimplementing
ObjectOutputStream to not have to allocate private data just used by
this implementation of ObjectOutputStream.

If there is a security manager installed, this method first calls the
security manager's `checkPermission` method with a
`SerializablePermission("enableSubclassImplementation")`
permission to ensure it's ok to enable subclassing.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if a security manager exists and its `checkPermission` method denies enabling subclassing. |
| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if an I/O error occurs while creating this stream |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityManager.html#checkPermission(java.security.Permission)`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/SerializablePermission.html`

## Public Methods

#### public void
**close**
()

Closes the stream. This method must be called to release any resources
associated with the stream.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | If an I/O error has occurred. |
|---|---|

#### public void
**defaultWriteObject**
()

Write the non-static and non-transient fields of the current class to
this stream. This may only be called from the writeObject method of the
class being serialized. It will throw the NotActiveException if it is
called otherwise.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying `OutputStream` |
|---|---|

#### public void
**flush**
()

Flushes the stream. This will write any buffered output bytes and flush
through to the underlying stream.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | If an I/O error has occurred. |
|---|---|

#### public [ObjectOutputStream.PutField](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.PutField.html)
**putFields**
()

Retrieve the object used to buffer persistent fields to be written to
the stream. The fields will be written to the stream when writeFields
method is called.

##### Returns

- an instance of the class Putfield that holds the serializable fields

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur |
|---|---|

#### public void
**reset**
()

Reset will disregard the state of any objects already written to the
stream. The state is reset to be the same as a new ObjectOutputStream.
The current point in the stream is marked as reset so the corresponding
ObjectInputStream will be reset at the same point. Objects previously
written to the stream will not be referred to as already being in the
stream. They will be written to the stream again.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if reset() is invoked while serializing an object. |
|---|---|

#### public void
**useProtocolVersion**
(int version)

Specify stream protocol version to use when writing the stream.

This routine provides a hook to enable the current version of
Serialization to write in a format that is backwards compatible to a
previous version of the stream format.

Every effort will be made to avoid introducing additional
backwards incompatibilities; however, sometimes there is no
other alternative.

##### Parameters

| version | use ProtocolVersion from java.io.ObjectStreamConstants. |
|---|---|

##### Throws

| [IllegalStateException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalStateException.html) | if called after any objects have been serialized. |
| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | if invalid version is passed in. |
| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#PROTOCOL_VERSION_1`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#PROTOCOL_VERSION_2`

#### public void
**write**
(byte\[\] buf)

Writes an array of bytes. This method will block until the bytes are
actually written.

##### Parameters

| buf | the data to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | If an I/O error has occurred. |
|---|---|

#### public void
**write**
(byte\[\] buf, int off, int len)

Writes a sub array of bytes.

##### Parameters

| buf | the data to be written |
| off | the start offset in the data |
| len | the number of bytes that are written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | If an I/O error has occurred. |
|---|---|

#### public void
**write**
(int val)

Writes a byte. This method will block until the byte is actually
written.

##### Parameters

| val | the byte to be written to the stream |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | If an I/O error has occurred. |
|---|---|

#### public void
**writeBoolean**
(boolean val)

Writes a boolean.

##### Parameters

| val | the boolean to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeByte**
(int val)

Writes an 8 bit byte.

##### Parameters

| val | the byte value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeBytes**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) str)

Writes a String as a sequence of bytes.

##### Parameters

| str | the String of bytes to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeChar**
(int val)

Writes a 16 bit char.

##### Parameters

| val | the char value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeChars**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) str)

Writes a String as a sequence of chars.

##### Parameters

| str | the String of chars to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeDouble**
(double val)

Writes a 64 bit double.

##### Parameters

| val | the double value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeFields**
()

Write the buffered fields to the stream.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
| [NotActiveException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/NotActiveException.html) | Called when a classes writeObject method was not called to write the state of the object. |
|---|---|

#### public void
**writeFloat**
(float val)

Writes a 32 bit float.

##### Parameters

| val | the float value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeInt**
(int val)

Writes a 32 bit int.

##### Parameters

| val | the integer value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeLong**
(long val)

Writes a 64 bit long.

##### Parameters

| val | the long value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public final void
**writeObject**
([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj)

Write the specified object to the ObjectOutputStream. The class of the
object, the signature of the class, and the values of the non-transient
and non-static fields of the class and all of its supertypes are
written. Default serialization for a class can be overridden using the
writeObject and the readObject methods. Objects referenced by this
object are written transitively so that a complete equivalent graph of
objects can be reconstructed by an ObjectInputStream.

Exceptions are thrown for problems with the OutputStream and for
classes that should not be serialized. All exceptions are fatal to the
OutputStream, which is left in an indeterminate state, and it is up to
the caller to ignore or recover the stream state.

##### Parameters

| obj | the object to write. |
|---|---|

##### Throws

| [InvalidClassException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/InvalidClassException.html) | Something is wrong with a class used by serialization. |
| [NotSerializableException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/NotSerializableException.html) | Some object to be serialized does not implement the java.io.Serializable interface. |
| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | Any exception thrown by the underlying OutputStream. |
|---|---|

#### public void
**writeShort**
(int val)

Writes a 16 bit short.

##### Parameters

| val | the short value to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeUTF**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) str)

Primitive data write of this String in
[modified UTF-8](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/DataInput#modified-utf-8)
format. Note that there is a
significant difference between writing a String into the stream as
primitive data or as an Object. A String instance written by writeObject
is written into the stream as a String initially. Future writeObject()
calls write references to the string into the stream.

##### Parameters

| str | the String to be written |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### public void
**writeUnshared**
([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj)

Writes an "unshared" object to the ObjectOutputStream. This method is
identical to writeObject, except that it always writes the given object
as a new, unique object in the stream (as opposed to a back-reference
pointing to a previously serialized instance). Specifically:

- An object written via writeUnshared is always serialized in the same manner as a newly appearing object (an object that has not been written to the stream yet), regardless of whether or not the object has been written previously.
- If writeObject is used to write an object that has been previously written with writeUnshared, the previous writeUnshared operation is treated as if it were a write of a separate object. In other words, ObjectOutputStream will never generate back-references to object data written by calls to writeUnshared.

While writing an object via writeUnshared does not in itself guarantee a unique reference to the object when it is deserialized, it allows a single object to be defined multiple times in a stream, so that multiple calls to readUnshared by the receiver will not conflict. Note that the rules described above only apply to the base-level object written with writeUnshared, and not to any transitively referenced sub-objects in the object graph to be serialized.

ObjectOutputStream subclasses which override this method can only be
constructed in security contexts possessing the
"enableSubclassImplementation" SerializablePermission; any attempt to
instantiate such a subclass without this permission will cause a
SecurityException to be thrown.

##### Parameters

| obj | object to write to stream |
|---|---|

##### Throws

| [NotSerializableException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/NotSerializableException.html) | if an object in the graph to be serialized does not implement the Serializable interface |
| [InvalidClassException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/InvalidClassException.html) | if a problem exists with the class of an object to be serialized |
| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if an I/O error occurs during serialization |
|---|---|

## Protected Methods

#### protected void
**annotateClass**
([Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> cl)

Subclasses may implement this method to allow class data to be stored in
the stream. By default this method does nothing. The corresponding
method in ObjectInputStream is resolveClass. This method is called
exactly once for each unique class in the stream. The class name and
signature will have already been written to the stream. This method may
make free use of the ObjectOutputStream to save any representation of
the class it deems suitable (for example, the bytes of the class file).
The resolveClass method in the corresponding subclass of
ObjectInputStream must read and use any data or objects written by
annotateClass.

##### Parameters

| cl | the class to annotate custom data for |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | Any exception thrown by the underlying OutputStream. |
|---|---|

#### protected void
**annotateProxyClass**
([Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> cl)

Subclasses may implement this method to store custom data in the stream
along with descriptors for dynamic proxy classes.

This method is called exactly once for each unique proxy class
descriptor in the stream. The default implementation of this method in
`ObjectOutputStream` does nothing.

The corresponding method in `ObjectInputStream` is
`resolveProxyClass`. For a given subclass of
`ObjectOutputStream` that overrides this method, the
`resolveProxyClass` method in the corresponding subclass of
`ObjectInputStream` must read any data or objects written by
`annotateProxyClass`.

##### Parameters

| cl | the proxy class to annotate custom data for |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | any exception thrown by the underlying `OutputStream` |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectInputStream.html#resolveProxyClass(java.lang.String[])`

#### protected void
**drain**
()

Drain any buffered data in ObjectOutputStream. Similar to flush but
does not propagate the flush to the underlying stream.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|

#### protected boolean
**enableReplaceObject**
(boolean enable)

Enable the stream to do replacement of objects in the stream. When
enabled, the replaceObject method is called for every object being
serialized.

If `enable` is true, and there is a security manager
installed, this method first calls the security manager's
`checkPermission` method with a
`SerializablePermission("enableSubstitution")` permission to
ensure it's ok to enable the stream to do replacement of objects in the
stream.

##### Parameters

| enable | boolean parameter to enable replacement of objects |
|---|---|

##### Returns

- the previous setting before this method was invoked

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if a security manager exists and its `checkPermission` method denies enabling the stream to do replacement of objects in the stream. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityManager.html#checkPermission(java.security.Permission)`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/SerializablePermission.html`

#### protected [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)
**replaceObject**
([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj)

This method will allow trusted subclasses of ObjectOutputStream to
substitute one object for another during serialization. Replacing
objects is disabled until enableReplaceObject is called. The
enableReplaceObject method checks that the stream requesting to do
replacement can be trusted. The first occurrence of each object written
into the serialization stream is passed to replaceObject. Subsequent
references to the object are replaced by the object returned by the
original call to replaceObject. To ensure that the private state of
objects is not unintentionally exposed, only trusted streams may use
replaceObject.

The ObjectOutputStream.writeObject method takes a parameter of type
Object (as opposed to type Serializable) to allow for cases where
non-serializable objects are replaced by serializable ones.

When a subclass is replacing objects it must insure that either a
complementary substitution must be made during deserialization or that
the substituted object is compatible with every field where the
reference will be stored. Objects whose type is not a subclass of the
type of the field or array element abort the serialization by raising an
exception and the object is not be stored.

This method is called only once when each object is first
encountered. All subsequent references to the object will be redirected
to the new object. This method should return the object to be
substituted or the original object.

Null can be returned as the object to be substituted, but may cause
NullReferenceException in classes that contain references to the
original object since they may be expecting an object instead of
null.

##### Parameters

| obj | the object to be replaced |
|---|---|

##### Returns

- the alternate object that replaced the specified one

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | Any exception thrown by the underlying OutputStream. |
|---|---|

#### protected void
**writeClassDescriptor**
([ObjectStreamClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamClass.html) desc)

Write the specified class descriptor to the ObjectOutputStream. Class
descriptors are used to identify the classes of objects written to the
stream. Subclasses of ObjectOutputStream may override this method to
customize the way in which class descriptors are written to the
serialization stream. The corresponding method in ObjectInputStream,
`readClassDescriptor`, should then be overridden to
reconstitute the class descriptor from its custom stream representation.
By default, this method writes class descriptors according to the format
defined in the Object Serialization specification.

Note that this method will only be called if the ObjectOutputStream
is not using the old serialization stream format (set by calling
ObjectOutputStream's `useProtocolVersion` method). If this
serialization stream is using the old format
(`PROTOCOL_VERSION_1`), the class descriptor will be written
internally in a manner that cannot be overridden or customized.

##### Parameters

| desc | class descriptor to write to the stream |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | If an I/O error has occurred. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectInputStream.html#readClassDescriptor()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#useProtocolVersion(int)`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectStreamConstants.html#PROTOCOL_VERSION_1`

#### protected void
**writeObjectOverride**
([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj)

Method used by subclasses to override the default writeObject method.
This method is called by trusted subclasses of ObjectInputStream that
constructed ObjectInputStream using the protected no-arg constructor.
The subclass is expected to provide an override method with the modifier
"final".

##### Parameters

| obj | object to be written to the underlying stream |
|---|---|

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if there are I/O errors while writing to the underlying stream |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#ObjectOutputStream()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/io/ObjectOutputStream.html#writeObject(java.lang.Object)`

#### protected void
**writeStreamHeader**
()

The writeStreamHeader method is provided so subclasses can append or
prepend their own header to the stream. It writes the magic number and
version to the stream.

##### Throws

| [IOException](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/IOException.html) | if I/O errors occur while writing to the underlying stream |
|---|---|