ObjectInputStream class

■ For its methods, see DataInput interface and InputStream class

It has these methods because it implements DataInput:

Plus it has these methods because it extends InputStream:

.readBoolean( ) Reads one byte and returns true or false if it was zero or non-zero. .readByte( ) Reads and returns a byte. .readChar( ) Reads and returns a char. .readDouble( ) Reads eight bytes and returns a double. .readFloat( ) Reads four bytes and returns a float. .readFully( byte[ ] ) Reads bytes into an array. .readFully( byte[ ], offset, len) Reads len bytes into an arry starting at offset. .readInt( ) Reads four bytes and returns an int. .readLine( ) Reads the next line of text from the input stream. .readLong( ) Reads eight bytes and returns a long. .readShort( ) Reads two bytes and returns a short. .readUnsignedByte( ) Reads a byte, extends it to int, returns it in the range 0 -255. .readUnsignedShort( ) Reads two bytes and returns an int in range 0 to 65535. .readUTF( ) Reads in a String encoded using a modified UTF-8 format. .skipBytes( num ) Skips num bytes of the input stream.

available( ) Tells how many bytes can be gotten without blocking. close( ) Close the stream. mark( int readAheadLimit ) Mark the present position in the stream. markSupported( ) Tell whether this stream supports mark(...). read( ) Read a single byte, returning it as the low end of an int. read( byte[ ] b ) Read bytes into a byte array. read( byte[ ] b, int off, int len) Read bytes into a portion of a byte array. ready( ) Tell whether this stream is ready to be read. reset( ) Reset the stream to the beginning. skip( long n ) Skip characters.

■ ObjectInputStream reads back:

(1) Serializable or Externalizable objects written with OutputStream.

(2) Bytes and primitives written with ObjectOutputStream

■ All object inputs, including Strings and Arrays, have to be cast upon receipt.

■ Restoral includes loading and initializations.

It adds one notable method which reads an object from the ObjectInputStream:

Object readObject( ) method

■ This sample code writes and then reads an int then two objects in order:

import java.io.*;

import java.util.*;

try {

FileOutputStream fos = new FileOutputStream("obj.tmp");

ObjectOutputStream oos = new ObjectOutputStream(fos);

int i = 123;

String s = "a String";

Date d = new Date( );

oos.writeInt( i ); // write it

oos.writeObject( s );

oos.writeObject( d );

oos.close( );

FileInputStream fis = new FileInputStream("obj.tmp");

ObjectInputStream ois = new ObjectInputStream(fis);

int i2 = ois.readInt( ); // read it

String s2 = (String) ois.readObject( );

Date d2 = (Date) ois.readObject( );

fis.close( );

}

catch (Exception e) { }