Chapter 31

Package java.io

CONTENTS

• DataInput
• DataOutput
• BufferedInputStream
• BufferedOutputStream
• ByteArrayInputStream
• ByteArrayOutputStream
• DataInputStream
• DataOutputStream
• File
• FileDescriptor
• FileInputStream
• FileOutputStream
• FilterInputStream
• FilterOutputStream
• InputStream
• LineNumberInputStream
• OutputStream
• PipedInputStream
• PipedOutputStream
• PrintStream
• PushbackInputStream
• RandomAccessFile
• SequenceInputStream
• StreamTokenizer
• StringBufferInputStream
• EOFException
• FileNotFoundException
• IOException
• InterruptedIOException
• UTFDataFormatException

The Java I/O package, also known as java.io, gives classes support for reading and writing data to and from different input and output devices, including files, strings, and other data sources. The I/O package includes classes for inputting streams of data, outputting streams of data, working with files, and tokenizing streams of data. Table 31.1 shows the contents of the java.io package, and Figure 31.1 illustrates the contents' hierarchy.

Figure 31.1: Contents of the java.io package.

DataInput

Object

See also: DataInputStream, DataOutput.

The DataInput interface describes an input stream that can read input data in a platform-independent manner; here is its definition:

public interface java.io.DataInput {
   // Methods
   public abstract boolean readBoolean();
   public abstract byte readByte();
   public abstract char readChar();
   public abstract double readDouble();
   public abstract float readFloat();
   public abstract void readFully(byte b[]);
   public abstract void readFully(byte b[], int off, int len);
   public abstract int readInt();
   public abstract String readLine();
   public abstract long readLong();
   public abstract short readShort();
   public abstract int readUnsignedByte();
   public abstract int readUnsignedShort();
   public abstract String readUTF();
   public abstract int skipBytes(int n);
}

public abstract boolean readBoolean() throws IOException

This method reads a Boolean value (byte) from the input stream. A value of 0 is interpreted as false, but all other values are interpreted as true.

the Boolean value read.

public abstract byte readByte() throws IOException

This method reads a signed byte (8-bit) value from the input stream.

the byte value read.

public abstract char readChar() throws IOException

This method reads a Unicode character (16-bit) value from the input stream.

the Unicode character value read.

public abstract double readDouble() throws IOException

This method reads a double (64-bit) value from the input stream.

the double value read.

public abstract float readFloat() throws IOException

This method reads a float (32-bit) value from the input stream.

the float value read.

public abstract void readFully(byte b[]) throws IOException

This method reads up to b.length bytes from the input stream into the byte array b, blocking until all bytes are read.

b is the byte array into which the data is read.

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

This method reads up to len bytes from the input stream into the byte array b beginning off bytes into the array, blocking until all bytes are read.

b is the byte array into which the data is read.

public abstract int readInt() throws IOException

This method reads an integer (32-bit) value from the input stream.

the integer value read.

public abstract String readLine() throws IOException

This method reads a line of text from the input stream.

a string containing the line of text read.

public abstract long readLong() throws IOException

This method reads a long (64-bit) value from the input stream.

the long value read.

EOFException if the end of the stream is reached before reading the value.

public abstract short readShort() throws IOException

This method reads a short (16-bit) value from the input stream.

the short value read.

public abstract int readUnsignedByte() throws IOException

This method reads an unsigned byte (8-bit) value from the input stream.

the unsigned byte value read.

public abstract int readUnsignedShort() throws IOException

This method reads an unsigned short (16-bit) value from the input stream.

the short value read.

public abstract String readUTF() throws IOException

This method reads a string encoded by using a modified UTF-8 format from the input stream.

the string read.

public abstract int skipBytes(int n) throws IOException

This method skips n bytes of data in the input stream, blocking until all bytes are skipped.

n is the number of bytes to skip.

DataOutput

Object

See also: DataOutputStream, DataInput.

The DataOutput interface describes an output stream that can write output data in a platform-independent manner; this is its definition:

public interface java.io.DataOutput {
   // Methods
   public abstract void write(byte b[]);
   public abstract void write(byte b[], int off, int len)
   public abstract void write(int b);
   public abstract void writeBoolean(boolean v);
   public abstract void writeByte(int v);
   public abstract void writeBytes(String s);
   public abstract void writeChar(int v);
   public abstract void writeChars(String s);
   public abstract void writeDouble(double v);
   public abstract void writeFloat(float v);
   public abstract void writeInt(int v);
   public abstract void writeLong(long v);
   public abstract void writeShort(int v);
   public abstract void writeUTF(String str);
}

public abstract void write(byte b[]) throws IOException

This method writes b.length bytes to the output stream from the byte array b, blocking until all bytes are written.

b is the byte array from which the data is written.

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

This method writes len bytes to the output stream from the byte array b beginning off bytes into the array, blocking until all bytes are written.

b is the byte array from which the data is written.

public abstract void write(int b) throws IOException

This method writes a byte value to the output stream, blocking until the byte is written.

b is the byte value to be written.

public abstract void writeBoolean(boolean v) throws IOException

This method writes a Boolean value to the output stream. The Boolean value true is written as the byte value 1, and false is written as the byte value 0.

v is the Boolean value to be written.

public abstract void writeByte(int v) throws IOException

This method writes a byte (8-bit) value to the output stream.

v is the byte value to be written.

public abstract void writeBytes(String s) throws IOException

This method writes a string to the output stream as a sequence of bytes.

s is the string to be written as bytes.

public abstract void writeChar(int v) throws IOException

This method writes a character (16-bit) value to the output stream.

v is the character value to be written.

public abstract void writeChars(String s) throws IOException

This method writes a string to the output stream as a sequence of characters.

s is the string to be written as characters.

public abstract void writeDouble(double v) throws IOException

This method writes a double (64-bit) value to the output stream.

v is the double value to be written.

public abstract void writeFloat(float v) throws IOException

This method writes a float (32-bit) value to the output stream.

v is the float value to be written.

public abstract void writeInt(int v) throws IOException

This method writes an integer (32-bit) value to the output stream.

v is the integer value to be written.

public abstract void writeLong(long v) throws IOException

This method writes a long (64-bit) value to the output stream.

v is the long value to be written.

public abstract void writeShort(int v) throws IOException

This method writes a short (16-bit) value to the output stream.

v is the short value to be written.

WriteUTF

DataOutput

public abstract void writeUTF(String str) throws IOException

This method encodes a string using a modified UTF-8 format and writes it to the output stream.

str is the string to be written.

FilenameFilter

Object

See also: File

The FilenameFilter interface describes a filename filter used to filter directory listings. Filename filters are used by the list method defined in the File class, as well as the AWT's FileDialog component; here is the definition for the interface:

public interface java.io.FilenameFilter {
// Methods
public abstract boolean accept(File dir, String name);
}

public abstract boolean accept(File dir, String name)

This method determines whether a file should be included in a directory listing.

dir is the directory in which the file is located.

BufferedInputStream

FilterInputStream

See also: BufferedOutputStream.

This class implements a buffered input stream, which allows you to read data from a stream without causing a call to the underlying system for each byte read. This is done by reading blocks of data into a buffer, where the data is readily accessible, independent of the underlying stream. Subsequent reads are much faster since they read from the buffer rather than the underlying input stream. Here is the definition for the BufferedInputStream class:

public class java.io.BufferedInputStream extends java.io.FilterInputStream
{
   // Member Variables
   protected byte buf[];
   protected int count;
   protected int marklimit;
   protected int markpos;
   protected int pos;

   // Constructors
   public BufferedInputStream(InputStream in);
   public BufferedInputStream(InputStream in, int size);

   // Methods
   public int available();
   public void mark(int readlimit);
   public boolean markSupported();
   public int read();
   public int read(byte b[], int off, int len);
   public void reset();
   public long skip(long n);
}

Following are the member variables defined in BufferedInputStream:

protected byte buf[]

This is the buffer where data is stored.

protected int count

This is the number of bytes of data currently in the buffer.

protected int marklimit

This is the maximum number of bytes that can be read before the marked position (markpos) is invalidated.

protected int markpos

This is the position in the buffer of the current mark, used to return to a particular location in the buffer with the mark and reset methods. The mark position is set to -1 if there is no current mark.

protected int pos

This is the current read position in the buffer.

public BufferedInputStream(InputStream in)

This constructor creates a new buffered input stream, with a default buffer size of 512 bytes, to read data from the in input stream.

in is the input stream to read data from.

public BufferedInputStream(InputStream in, int size)

This constructor creates a new buffered input stream, with a buffer size of size bytes, to read data from the in input stream.

in is the input stream to read data from.

public int available() throws IOException

This method determines the number of bytes that can be read from the input stream without blocking. That number is calculated by adding the number of free bytes in the buffer and the number of bytes available in the input stream.

the number of available bytes.

public void mark(int readlimit)

This method marks the current read position in the input stream. The reset method can be used to reset the read position to this mark; subsequent reads will read data beginning at the mark position. The mark position is invalidated after readlimit bytes have been read.

readlimit is the maximum number of bytes that can be read before the mark position becomes invalid.

public boolean markSupported()

This method determines whether the input stream supports the mark and reset methods.

true if the mark and reset methods are supported; false otherwise.

public int read() throws IOException

This method reads a byte value from the buffered input stream, blocking until the byte is read.

an integer representing the byte value read, or -1 if the end of the stream is reached.

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

This method reads up to len bytes from the buffered input stream into the byte array b beginning off bytes into the array, blocking until all bytes are read.

b is the byte array into which the data is read.

public void reset() throws IOException

This method resets the read position in the input stream to the current mark position, as set by the mark method.

IOException if the stream has not been marked or if the mark is invalid.

public long skip(long n) throws IOException

This method skips n bytes of data in the input stream.

n is the number of bytes to skip.

BufferedOutputStream

FilterOutputStream

See also: BufferedInputStream.

This class implements a buffered output stream, which enables you to write data to a stream without causing a call to the underlying system for each byte written. This is done by writing blocks of data into a buffer rather than directly to the underlying output stream. The buffer is then written to the underlying output stream when the buffer fills up or is flushed or when the stream is closed. This is the definition for the BufferedOutputStream class:

public class java.io.BufferedOutputStream extends java.io.FilterOutputStream {
   // Member Variables
   protected byte buf[];
   protected int count;

   // Constructors
   public BufferedOutputStream(OutputStream out);
   public BufferedOutputStream(OutputStream out, int size);

   // Methods
   public void flush();
   public void write(byte b[], int off, int len);
   public void write(int b);
}

Following are the member variables defined in BufferedOutputStream:

protected byte buf[]

This is the buffer where data is stored.

protected int count

This is the number of bytes of data currently in the buffer.

public BufferedOutputStream(OutputStream out)

This constructor creates a new buffered output stream, with a default buffer size of 512 bytes, to write data to the out output stream.

out is the output stream to write data to.

public BufferedOutputStream(OutputStream out, int size)

This constructor creates a new buffered output stream, with a buffer size of size bytes, to write data to the out output stream.

out is the output stream to write data to.

public void flush() throws IOException

This method flushes the output stream, resulting in any buffered data being written to the underlying output stream.

IOException if an I/O error occurs.

public void write(byte b[], int off, int len) throws IOException

This method writes len bytes to the buffered output stream from the byte array b beginning off bytes into the array.

b is the byte array from which the data is written.

public void write(int b) throws IOException

This method writes a byte value to the buffered output stream.

b is the byte value to be written.

ByteArrayInputStream

InputStream

See also: ByteArrayOutputStream.

The ByteArrayInputStream class implements an input stream whose data is read from an array of bytes; here is the definition for the class:

public class java.io.ByteArrayInputStream extends java.io.InputStream {
   // Member Variables
   protected byte buf[];
   protected int count;
   protected int pos;

   // Constructors
   public ByteArrayInputStream(byte b[]);
   public ByteArrayInputStream(byte b[], int off, int len);

  // Methods
  public int available();
  public int read();
  public int read(byte b[], int off, int len);
  public void reset();
  public long skip(long n);
}

Following are the member variables defined in ByteArrayInputStream:

protected byte buf[]

This is the buffer where data is stored.

protected int count

This is the number of bytes of data currently in the buffer.

protected int pos

This is the current read position in the buffer.

public ByteArrayInputStream(byte b[])

This constructor creates a new input stream from the byte array b. Note that the byte array is not copied to create the stream.

b is the byte array from which the data is read.

public ByteArrayInputStream(byte b[], int off, int len)

This constructor creates a new input stream of size len from the byte array b beginning off bytes into the array. Note that the byte array is not copied to create the stream.

b is the byte array from which the data is read.

public int available()

This method determines the number of bytes that can be read from the input stream.

the number of available bytes.

public int read()

This method reads a byte value from the input stream.

an integer representing the byte value read, or -1 if the end of the stream is reached.

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

This method reads up to len bytes from the input stream into the byte array b beginning off bytes into the array.

b is the byte array into which the data is read.

public void reset()

This method resets the read position to the beginning of the input stream.

reset in class InputStream.

public long skip(long n)

This method skips n bytes of data in the input stream.

n is the number of bytes to skip.

ByteArrayOutputStream

OutputStream

See also: ByteArrayInputStream.

The ByteArrayOutputStream class implements an output stream whose data is written to an array of bytes. The byte array automatically grows as data is written to it. Here is the definition for the class:

public class java.io.ByteArrayOutputStream extends java.io.OutputStream {
  // Member Variables
  protected byte buf[];
  protected int count;

  // Constructors
  public ByteArrayOutputStream();
  public ByteArrayOutputStream(int size);

  // Methods
  public void reset();
  public int size();
  public byte[] toByteArray();
  public String toString();
  public String toString(int hibyte);
  public void write(byte b[], int off, int len);
  public void write(int b);
  public void writeTo(OutputStream out);
}

Following are the member variables defined in ByteArrayOutputStream:

protected byte buf[]

This is the buffer where data is stored.

protected int count

This is the number of bytes of data currently in the buffer.

public ByteArrayOutputStream()

This constructor creates a new output stream with a default buffer size of 32 bytes. The size of the buffer automatically grows as data is written to it.

public ByteArrayOutputStream(int size)

This constructor creates a new output stream with an initial size of size bytes. The size of the buffer automatically grows as data is written to it.

size is the initial size of the buffer.

public void reset()

This method resets the contents of the underlying byte array by setting the count member variable to zero, resulting in the accumulated data being discarded.

public int size()

This method returns the current size of the buffer, which is stored in the count member variable.

the current size of the buffer.

public byte[] toByteArray()

This method creates a new byte array containing the data currently stored in the underlying byte array associated with the output stream.

a byte array containing the current data stored in the output stream.

public String toString()

This method creates a new string containing the data currently stored in the underlying byte array associated with the output stream.

a string containing the current data stored in the output stream.

public String toString(int hibyte)

This method creates a new string containing the data currently stored in the underlying byte array associated with the output stream, with the top 8 bits of each string character set to hibyte.

hibyte is the high byte value for each character.

public void write(byte b[], int off, int len)

This method writes len bytes to the output stream from the byte array b beginning off bytes into the array.

b is the byte array from which the data is written.

public void write(int b)

This method writes a byte value to the output stream.

b is the byte value to be written.

public void writeTo(OutputStream out) throws IOException

This method writes the contents of the underlying byte array to another output

stream.

out is the output stream to write to.

DataInputStream

FilterInputStream

See also: DataOutputStream.

The DataInputStream class implements an input stream that can read Java primitive data types in a platform-independent manner. Here is the definition for the class:

public class java.io.DataInputStream extends java.io.FilterInputStream
  implements java.io.DataInput {
  // Constructors
  public DataInputStream(InputStream in);

  // Methods
  public final int read(byte b[]);
  public final int read(byte b[], int off, int len);
  public final boolean readBoolean();
  public final byte readByte();
  public final char readChar();
  public final double readDouble();
  public final float readFloat();
  public final void readFully(byte b[]);
  public final void readFully(byte b[], int off, int len);
  public final int readInt();
  public final String readLine();
  public final long readLong();
  public final short readShort();
  public final int readUnsignedByte();
  public final int readUnsignedShort();
  public final String readUTF();
  public final static String readUTF(DataInput in);
  public final int skipBytes(int n);
}

public DataInputStream(InputStream in)

This method creates a new data input stream to read data from the in input stream.

in is the input stream to read data from.

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

This method reads up to b.length bytes from the data input stream into the byte array b, blocking until all bytes are read.

b is the byte array into which the data is read.

the actual number of bytes read, or -1 if the end of the stream is reached.

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

This method reads up to len bytes from the data input stream into the byte array b beginning off bytes into the array, blocking until all bytes are read.

b is the byte array into which the data is read.

public final boolean readBoolean() throws IOException

This method reads a Boolean value (byte) from the data input stream, blocking until the byte is read. A value of 0 is interpreted as false, and all other values are interpreted as true.

the Boolean value read.

public final byte readByte() throws IOException

This method reads a signed byte (8-bit) value from the data input stream, blocking until the byte is read.

the byte value read.

public final char readChar() throws IOException

This method reads a character (16-bit) value from the data input stream, blocking until both bytes are read.

the character value read.

public final double readDouble() throws IOException

This method reads a double (64-bit) value from the data input stream, blocking until all eight bytes are read.

the double value read.

public final float readFloat() throws IOException

This method reads a float (32-bit) value from the data input stream, blocking until all four bytes are read.

the float value read.

ReadFully

DataInputStream

public final void readFully(byte b[]) throws IOException

This method reads up to b.length bytes from the data input stream into the byte array b, blocking until all bytes are read.

b is the byte array into which the data is read.

public final void readFully(byte b[], int off, int len) throws IOException

This method reads up to len bytes from the data input stream into the byte array b beginning off bytes into the array, blocking until all bytes are read.

b is the byte array into which the data is read.

public final int readInt() throws IOException

This method reads an integer (32-bit) value from the data input stream, blocking until all four bytes are read.

the integer value read.

public final String readLine() throws IOException

This method reads a line of text from the data input stream, blocking until either a newline character (\n) or a carriage return character (\r) is read.

a string containing the line of text read.

public final long readLong() throws IOException

This method reads a long (64-bit) value from the data input stream, blocking until all eight bytes are read.

the long value read.

public final short readShort() throws IOException

This method reads a signed short (16-bit) value from the data input stream, blocking until both bytes are read.

the short value read.

public final int readUnsignedByte() throws IOException

This method reads an unsigned byte (8-bit) value from the data input stream, blocking until the byte is read.

the unsigned byte value read.

public final int readUnsignedShort() throws IOException

This method reads an unsigned short (16-bit) value from the data input stream, blocking until both bytes are read.

the unsigned short value read.

public final String readUTF() throws IOException

This method reads a string that has been encoded using a modified UTF-8 format from the data input stream, blocking until all bytes are read.

the string read.

public final static String readUTF(DataInput in) throws IOException

This method reads a string from the in data input stream that has been encoded using a modified UTF-8 format, blocking until all bytes are read.

in is the data input stream to read the string from.

public final int skipBytes(int n) throws IOException

This method skips n bytes of data in the data input stream, blocking until all bytes are skipped.

n is the number of bytes to skip.

DataOutputStream

FilterOutputStream

See also: DataInputStream.

The DataOutputStream class implements an output stream that can write Java primitive data types in a platform-independent manner; this is the definition for the class:

public class java.io.DataOutputStream extends java.io.FilterOutputStream
  implements java.io.DataOutput {
  // Member Variables
  protected int written;

  // Constructors
  public DataOutputStream(OutputStream out);

  // Methods
  public void flush();
  public final int size();
  public void write(byte b[], int off, int len);
  public void write(int b);
  public final void writeBoolean(boolean v);
  public final void writeByte(int v);
  public final void writeBytes(String s);
  public final void writeChar(int v);
  public final void writeChars(String s);
  public final void writeDouble(double v);
  public final void writeFloat(float v);
  public final void writeInt(int v);
  public final void writeLong(long v);
  public final void writeShort(int v);
  public final void writeUTF(String str);
}

Following are the member variables defined in DataOutputStream:

protected int written

This is the number of bytes written to the output stream so far.

public DataOutputStream(OutputStream out)

This method creates a new data output stream to write data to the out output stream.

out is the output stream to write data to.

public void flush() throws IOException

This method flushes the data output stream, resulting in any buffered data being written to the underlying output stream.

IOException if an I/O error occurs.

public final int size()

This method returns the number of bytes written to the data output stream thus far, which is stored in the written member variable.

the number of bytes written to the data output stream so far.

public void write(byte b[], int off, int len) throws IOException

This method writes len bytes to the data output stream from the byte array b beginning off bytes into the array.

b is the byte array from which the data is written.

public void write(int b) throws IOException

This method writes a byte value to the data output stream.

b is the byte value to be written.

public final void writeBoolean(boolean v) throws IOException

This method writes a Boolean value to the data output stream. The Boolean value true is written as the byte value 1, and false is written as the byte value 0.

v is the Boolean value to be written.

public final void writeByte(int v) throws IOException

This method writes a byte (8-bit) value to the data output stream.

v is the byte value to be written.

public final void writeBytes(String s) throws IOException

This method writes a string to the data output stream as a sequence of bytes.

s is the string to be written as bytes.

public final void writeChar(int v) throws IOException

This method writes a character (16-bit) value to the data output stream.

v is the character value to be written.

IOException if an I/O error occurs.

public final void writeChars(String s) throws IOException

This method writes a string to the data output stream as a sequence of characters.

s is the string to be written as characters.

public final void writeDouble(double v) throws IOException

This method writes a double (64-bit) value to the data output stream.

v is the double value to be written.

public final void writeFloat(float v) throws IOException

This method writes a float (32-bit) value to the data output stream.

v is the float value to be written.

public final void writeInt(int v) throws IOException

This method writes an integer (32-bit) value to the data output stream.

v is the integer value to be written.

public final void writeLong(long v) throws IOException

This method writes a long (64-bit) value to the data output stream.

v is the long value to be written.

public final void writeShort(int v) throws IOException

This method writes a short (16-bit) value to the data output stream.

v is the short value to be written.

public final void writeUTF(String str) throws IOException

This method encodes a string using a modified UTF-8 format and writes it to the data output stream.

str is the string to be written.

File

Object

See also: FileDescriptor.

The File class implements a filename in a platform-independent manner; it gives you the functionality needed to work with filenames and directories without having to deal with the complexities associated with filenames on a particular platform. Here is the class definition:

public class java.io.File extends java.lang.Object {
  // Member Variables
  public final static String pathSeparator;
  public final static char pathSeparatorChar;
  public final static String separator;
  public final static char separatorChar;

  // Constructors
  public File(File dir, String name);
  public File(String path);
  public File(String path, String name);

  // Methods
  public boolean canRead();
  public boolean canWrite();
  public boolean delete();
  public boolean equals(Object obj);
  public boolean exists();
  public String getAbsolutePath();
  public String getName();
  public String getParent();
  public String getPath();
  public int hashCode();
  public boolean isAbsolute();
  public boolean isDirectory();
  public boolean isFile();
  public long lastModified();
  public long length();
  public String[] list();
  public String[] list(FilenameFilter filter);
  public boolean mkdir();
  public boolean mkdirs();
  public boolean renameTo(File dest);
  public String toString();
}

Following are the member variables defined in File:

public final static String pathSeparator

This is the platform-specific path separator string.

public final static char pathSeparatorChar

This is the platform-specific path separator character, which separates filenames in a path list.

public final static String separator

This is the platform-specific file separator string.

public final static char separatorChar

This is the platform-specific file separator character, which separates the file and directory components in a filename.

public File(File dir, String name)

This constructor creates the filename of an underlying file based on the specified directory and filename. If no directory is specified in the dir argument, the constructor assumes the file is in the current directory.

dir is the directory where the file is located.

public File(String path)

This constructor creates the filename of an underlying file based on the specified file path.

path is the file path.

public File(String path, String name)

This constructor creates the filename of an underlying file based on the specified path and filename.

path is the path where the file is located.

public boolean canRead()

This method determines whether the underlying file can be read from. In other words, if the file is readable, canRead determines whether the file exists.

true if the file can be read from; false otherwise.

SecurityException if the application doesn't have read access to the file.

public boolean canWrite()

This method determines whether the underlying file can be written to. In other words, if the file is writeable, canWrite determines whether the file exists.

true if the file can be written to; false otherwise.

public boolean delete()

This method deletes the underlying file.

true if the file is deleted; false otherwise.

public boolean equals(Object obj)

This method compares the path name of the obj File object to the path name of the underlying file.

obj is the object to compare with.

public boolean exists()

This method determines whether the underlying file exists by opening it for reading and then closing it.

true if the file exists; false otherwise.

public String getAbsolutePath()

This method determines the platform-specific absolute path name of the underlying file.

the absolute path name of the file.

public String getName()

This method determines the filename of the underlying file, which doesn't include any path information.

the filename of the file.

public String getParent()

This method determines the parent directory of the underlying file, which is the immediate directory where the file is located.

the parent directory of the file, or null if the file is located in the root directory.

public String getPath()

This method determines the path name of the underlying file.

the path name of the file.

public int hashCode()

This method calculates a hash code for the underlying file.

a hash code for the file.

public boolean isAbsolute()

This method determines whether this object represents an absolute path name for the underlying file. Note that absolute path names are platform specific.

true if the path name for the file is absolute; false otherwise.

public boolean isDirectory()

This method determines whether the underlying file is actually a directory.

true if the file is actually a directory; false otherwise.

public boolean isFile()

This method determines whether the underlying file is a normal file-that is, not a directory.

true if the file is a normal file; false otherwise.

public long lastModified()

This method determines the last modification time of the underlying file. Note that this time is system specific and is not absolute; in other words, use the time only to compare against other times retrieved by using this method.

the last modification time of the file, or 0 if the file doesn't exist.

public long length()

This method determines the length in bytes of the underlying file.

the length of the file in bytes.

public String[] list()

This method builds a list of the filenames in the directory represented by this object. Note that the underlying file must actually be a directory for this method to work.

an array containing the filenames located in the directory.

public String[] list(FilenameFilter filter)

This method builds a list, using the specified filename filter, of the filenames in the directory represented by this object. Note that the underlying file must actually be a directory for this method to work.

filter is the filename filter used to select the filenames.

public boolean mkdir()

This method creates a directory based on the path name specified by this object.

true if the directory is created; false otherwise.