Chapter 11
The java.io Package

ObjectInput

Name

ObjectInput

Synopsis

Interface Name:

java.io.ObjectInput

Super-interface:

java.io.DataInput

Immediate Sub-interfaces:

None

Implemented By:

java.io.ObjectInputStream

Availability:

New as of JDK 1.1

The ObjectInput interface extends the DataInput interface for object serialization. While DataInput defines methods for reading primitive types from a stream, ObjectInput defines methods for reading objects and arrays of bytes.

Interface Declaration

public abstract interface java.io.ObjectInput extends java.io.DataInput {
  // Methods
  public abstract int available();
  public abstract void close();
  public abstract int read();
  public abstract int read(byte[] b);
  public abstract int read(byte[] b, int off, int len);
  public abstract Object readObject();
  public abstract long skip(long n);
}

Methods

available

public abstract int available() throws IOException

Returns

The number of bytes that can be read without blocking.

Throws

IOException: If any kind of I/O error occurs.

Description

This method returns the number of bytes that can be read from the stream without accessing a physical device, like a disk or a network.

close

public abstract void close() throws IOException

Throws

IOException: If any kind of I/O error occurs.

Description

This method closes the stream and releases any system resources associated with it.

read

public abstract int read() throws IOException

Returns

The next byte of data or -1 if the end of the stream is encountered.

Throws

IOException: If any kind of I/O error occurs.

Description

This method returns the next byte of data from the stream. The method blocks until the byte is read, the end of stream is detected, or an exception is thrown.

public abstract int read(byte[] b) throws IOException

Parameters

b: An array of bytes to be filled from the stream.

Returns

The actual number of bytes read or -1 if the end of the stream is encountered immediately.

Throws

IOException: If any kind of I/O error occurs.

Description

This method reads bytes from the stream to fill the given array. The method blocks until some data is available.

 public abstract int read(byte[] b, int off, int len) throws IOException

Parameters

b

An array of bytes to be filled from the stream.

off

An offset into the array.

len

The number of bytes to read.

Returns

The actual number of bytes read or -1 if the end of the stream is encountered immediately.

Throws

IOException: If any kind of I/O error occurs.

Description

This method reads up to len bytes of input into the given array starting at index off. The method blocks until some data is available.

readObject

 public abstract Object readObject() throws ClassNotFoundException, IOException

Returns

An Object that has been deserialized from the stream.

Throws

ClassNotFoundException

If the class of the serialized object cannot be found in the run-time environment.

IOException

If any kind of I/O error occurs.

Description

This method reads and returns an object instance from the stream; in other words, it deserializes an object from the stream. The class that implements this interface determines exactly how the object is to be read.

skip

public abstract long skip(long n) throws IOException

Parameters

n: The number of bytes to skip.

Returns

The actual number of bytes skipped.

Throws

IOException: If any kind of I/O error occurs.

Description

This method skips n bytes of input.

Inherited Methods

Method	Inherited From	Method	Inherited From
`readBoolean()`	`DataInput`	`readByte()`	`DataInput`
`readChar()`	`DataInput`	`readDouble()`	`DataInput`
`readFloat(byte[])`	`DataInput`	`readFully(byte[])`	`DataInput`
`readFully(byte[], int, int)`	`DataInput`	`readInt()`	`DataInput`
`readLine()`	`DataInput`	`readLong()`	`DataInput`
`readShort()`	`DataInput`	`readUnsignedByte()`	`DataInput`
`readUnsignedChar()`	`DataInput`	`readUTF()`	`DataInput`
`skipBytes(int)`	`DataInput`