Java in a Nutshell, 5th Edition [Electronic resources]

The java.io package is large, but most of the classes it contains fall into a well-structured hierarchy. Most of the package consists of byte streamssubclasses of InputStream or OutputStream and character streamssubclasses of Reader or Writer. Each of these stream subtypes has a specific purpose, and, despite its size, java.io is a straightforward package to understand and to use. In Java 1.4, the java.io package was complemented by a "New I/O API" defined in the java.nio package and its subpackages. The java.nio package is totally new, although it included some compatibility with the classes in this package. It was designed for high-performance I/O, particularly for use in servers and has a lower-level API than this package does. The I/O facilities of java.io are still quite adequate for most of the I/O required by typical client-side applications.

Before we consider the stream classes that comprise the bulk of this package, let''''s examine the important nonstream classes. File represents a file or directory name in a system-independent way and provides methods for listing directories, querying file attributes, and renaming and deleting files. FilenameFilter is an interface that defines a method that accepts or rejects specified filenames. It is used by File to specify what types of files should be included in directory listings. RandomAccessFile allows you to read from or write to arbitrary locations of a file. Often, though, you''''ll prefer sequential access to a file and should use one of the stream classes.

InputStream and OutputStream are abstract classes that define methods for reading and writing bytes. Their subclasses allow bytes to be read from and written to a variety of sources and sinks. FileInputStream and FileOutputStream read from and write to files. ByteArrayInputStream and ByteArrayOutputStream read from and write to an array of bytes in memory. PipedInputStream reads bytes from a PipedOutputStream, and PipedOutputStream writes bytes to a PipedInputStream. These classes work together to implement a

pipe for communication between threads.

FilterInputStream and FilterOutputStream are special; they filter input and output bytes. When you create a FilterInputStream, you specify an InputStream for it to filter. When you call the read( ) method of a FilterInputStream, it calls the read( ) method of its InputStream, processes the bytes it reads, and returns the filtered bytes. Similarly, when you create a FilterOutputStream, you specify an OutputStream to be filtered. Calling the write( ) method of a FilterOutputStream causes it to process your bytes in some way and then pass those filtered bytes to the write( ) method of its OutputStream.

FilterInputStream and FilterOutputStream do not perform any filtering themselves; this is done by their subclasses. BufferedInputStream and BufferedOutputStream are filtered streams that provide input and output buffering and can increase I/O efficiency. DataInputStream reads raw bytes from a stream and interprets them in various binary formats. It has various methods to read primitive Java data types in their standard binary formats. DataOutputStream allows you to write Java primitive data types in binary format. The ObjectInputStream and ObjectOutputStream classes are special. These byte-stream classes are used for serializing and deserializing the internal state of objects for storage or interprocess communication.

The byte streams just described are complemented by an analogous set of character input and output streams. Reader is the superclass of all character input streams, and Writer is the superclass of all character output streams. Most of the Reader and Writer streams have obvious byte-stream analogs. BufferedReader is a commonly used stream; it provides buffering for efficiency and also has a readLine( ) method to read a line of text at a time. PrintWriter is another very common stream; its methods allow output of a textual representation of any primitive Java type or of any object (via the object''''s toString( ) method).

Java 5.0 adds the Closeable and Flushable interfaces to identify types that have close( ) and flush( ) methods. All streams have a close( ) method and implement the Closeable interface. And all byte and character output streams have a flush( ) method and implement Flushable. In a related change, all character output streams (and the byte stream PrintStream ) implement the (new in Java 5.0) interface java.lang.Appendable, making them suitable for use with the java.util.Formatter class. Similarly, all character input streams implement the java.lang.Readable interface, making them suitable for use with the java.util.Scanner class. Finally, both PrintStream and PrintWriter have been enhanced in two ways for Java 5.0. Both now include constructors for creating a stream that writes directly to a file. And both include formatted-text output methods printf( ) and format( ). See java.util.Formatter for details.

Interfaces

public interface 
Closeable ;
public interface 
DataInput ;
public interface 
DataOutput ;
public interface 
Externalizable  extends Serializable;
public interface 
FileFilter ;
public interface 
FilenameFilter ;
public interface 
Flushable ;
public interface 
ObjectInput  extends DataInput;
public interface 
ObjectInputValidation ;
public interface 
ObjectOutput  extends DataOutput;
public interface 
ObjectStreamConstants ;
public interface 
Serializable ;

Classes

public class 
File  implements Serializable, Comparable<File>;
public final class 
FileDescriptor ;
public final class 
FilePermission  extends java.security.Permission implements 
Serializable;
public abstract class 
InputStream  implements Closeable;
public class 
ByteArrayInputStream  extends InputStream;
public class 
FileInputStream  extends InputStream;
public class 
FilterInputStream  extends InputStream;
public class 
BufferedInputStream  extends FilterInputStream;
public class 
DataInputStream  extends FilterInputStream implements 
DataInput;
public class 
LineNumberInputStream  extends FilterInputStream;
public class 
PushbackInputStream  extends FilterInputStream;
public class 
ObjectInputStream  extends InputStream implements ObjectInput, 
ObjectStreamConstants;
public class 
PipedInputStream  extends InputStream;
public class 
SequenceInputStream  extends InputStream;
public class 
StringBufferInputStream  extends InputStream;
public abstract static class 
ObjectInputStream.GetField ;
public abstract static class 
ObjectOutputStream.PutField ;
public class 
ObjectStreamClass  implements Serializable;
public class 
ObjectStreamField  implements Comparable<Object>;
public abstract class 
OutputStream  implements Closeable, Flushable;
public class 
ByteArrayOutputStream  extends OutputStream;
public class 
FileOutputStream  extends OutputStream;
public class 
FilterOutputStream  extends OutputStream;
public class 
BufferedOutputStream  extends FilterOutputStream;
public class 
DataOutputStream  extends FilterOutputStream implements 
DataOutput;
public class 
PrintStream  extends FilterOutputStream implements Appendable, 
Closeable;
public class 
ObjectOutputStream  extends OutputStream implements ObjectOutput, 
ObjectStreamConstants;
public class 
PipedOutputStream  extends OutputStream;
public class 
RandomAccessFile  implements Closeable, DataInput, DataOutput;
public abstract class 
Reader  implements Closeable, Readable;
public class 
BufferedReader  extends Reader;
public class 
LineNumberReader  extends BufferedReader;
public class 
CharArrayReader  extends Reader;
public abstract class 
FilterReader  extends Reader;
public class 
PushbackReader  extends FilterReader;
public class 
InputStreamReader  extends Reader;
public class 
FileReader  extends InputStreamReader;
public class 
PipedReader  extends Reader;
public class 
StringReader  extends Reader;
public final class 
SerializablePermission  extends java.security.BasicPermission;
public class 
StreamTokenizer ;
public abstract class 
Writer  implements Appendable, Closeable, Flushable;
public class 
BufferedWriter  extends Writer;
public class 
CharArrayWriter  extends Writer;
public abstract class 
FilterWriter  extends Writer;
public class 
OutputStreamWriter  extends Writer;
public class 
FileWriter  extends OutputStreamWriter;
public class 
PipedWriter  extends Writer;
public class 
PrintWriter  extends Writer;
public class 
StringWriter  extends Writer;

Exceptions

public class 
IOException  extends Exception;
public class 
CharConversionException  extends IOException;
public class 
EOFException  extends IOException;
public class 
FileNotFoundException  extends IOException;
public class 
InterruptedIOException  extends IOException;
public abstract class 
ObjectStreamException  extends IOException;
public class 
InvalidClassException  extends ObjectStreamException;
public class 
InvalidObjectException  extends ObjectStreamException;
public class 
NotActiveException  extends ObjectStreamException;
public class 
NotSerializableException  extends ObjectStreamException;
public class 
OptionalDataException  extends ObjectStreamException;
public class 
StreamCorruptedException  extends ObjectStreamException;
public class 
WriteAbortedException  extends ObjectStreamException;
public class 
SyncFailedException  extends IOException;
public class 
UnsupportedEncodingException  extends IOException;
public class 
UTFDataFormatException  extends IOException;