Class FileInputStream

Constructor Detail

• FileInputStream

  public FileInputStream(String name)
                  throws FileNotFoundException

  Creates a FileInputStream by opening a connection to an actual file, the file named by the path name name in the file system. A new FileDescriptor object is created to represent this file connection.

  First, if there is a security manager, its checkRead method is called with the name argument as its argument.

  If the named file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading then a FileNotFoundException is thrown.

  Parameters:

  name - the system-dependent file name.

  Throws:

  FileNotFoundException - if the file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading.

  SecurityException - if a security manager exists and its checkRead method denies read access to the file.

  See Also:

  SecurityManager.checkRead(java.lang.String)

• FileInputStream

  public FileInputStream(File file)
                  throws FileNotFoundException

  Creates a FileInputStream by opening a connection to an actual file, the file named by the File object file in the file system. A new FileDescriptor object is created to represent this file connection.

  First, if there is a security manager, its checkRead method is called with the path represented by the file argument as its argument.

  If the named file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading then a FileNotFoundException is thrown.

  Parameters:

  file - the file to be opened for reading.

  Throws:

  FileNotFoundException - if the file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading.

  SecurityException - if a security manager exists and its checkRead method denies read access to the file.

  See Also:

  File.getPath(), SecurityManager.checkRead(java.lang.String)

• FileInputStream

  public FileInputStream(FileDescriptor fdObj)

  Creates a FileInputStream by using the file descriptor fdObj, which represents an existing connection to an actual file in the file system.

  If there is a security manager, its checkRead method is called with the file descriptor fdObj as its argument to see if it's ok to read the file descriptor. If read access is denied to the file descriptor a SecurityException is thrown.

  If fdObj is null then a NullPointerException is thrown.

  This constructor does not throw an exception if fdObj is invalid. However, if the methods are invoked on the resulting stream to attempt I/O on the stream, an IOException is thrown.

  Parameters:

  fdObj - the file descriptor to be opened for reading.

  Throws:

  SecurityException - if a security manager exists and its checkRead method denies read access to the file descriptor.

  See Also:

  SecurityManager.checkRead(java.io.FileDescriptor)

Method Detail

• read

  public int read()
           throws IOException

  Reads a byte of data from this input stream. This method blocks if no input is yet available.

  Specified by:

  read in class InputStream

  Returns:

  the next byte of data, or -1 if the end of the file is reached.

  Throws:

  IOException - if an I/O error occurs.

• read

  public int read(byte[] b)
           throws IOException

  Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

  Overrides:

  read in class InputStream

  Parameters:

  b - the buffer into which the data is read.

  Returns:

  the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.

  Throws:

  IOException - if an I/O error occurs.

  See Also:

  InputStream.read(byte[], int, int)

• read

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

  Reads up to len bytes of data from this input stream into an array of bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

  Overrides:

  read in class InputStream

  Parameters:

  b - the buffer into which the data is read.

  off - the start offset in the destination array b

  len - the maximum number of bytes read.

  Returns:

  the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.

  Throws:

  NullPointerException - If b is null.

  IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

  IOException - if an I/O error occurs.

  See Also:

  InputStream.read()

• skip

  public long skip(long n)
            throws IOException

  Skips over and discards n bytes of data from the input stream.

  The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. If n is negative, an IOException is thrown, even though the skip method of the InputStream superclass does nothing in this case. The actual number of bytes skipped is returned.

  This method may skip more bytes than are remaining in the backing file. This produces no exception and the number of bytes skipped may include some number of bytes that were beyond the EOF of the backing file. Attempting to read from the stream after skipping past the end will result in -1 indicating the end of the file.

  Overrides:

  skip in class InputStream

  Parameters:

  n - the number of bytes to be skipped.

  Returns:

  the actual number of bytes skipped.

  Throws:

  IOException - if n is negative, if the stream does not support seek, or if an I/O error occurs.

• available

  public int available()
                throws IOException

  Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

  In some cases, a non-blocking read (or skip) may appear to be blocked when it is merely slow, for example when reading large files over slow networks.

  Overrides:

  available in class InputStream

  Returns:

  an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking.

  Throws:

  IOException - if this file input stream has been closed by calling close or an I/O error occurs.

• close

  public void close()
             throws IOException

  Closes this file input stream and releases any system resources associated with the stream.

  If this stream has an associated channel then the channel is closed as well.

  Specified by:

  close in interface Closeable

  Specified by:

  close in interface AutoCloseable

  Overrides:

  close in class InputStream

  Throws:

  IOException - if an I/O error occurs.

• getFD

  public final FileDescriptor getFD()
                             throws IOException

  Returns the FileDescriptor object that represents the connection to the actual file in the file system being used by this FileInputStream.

  Returns:

  the file descriptor object associated with this stream.

  Throws:

  IOException - if an I/O error occurs.

  See Also:

  FileDescriptor

• getChannel

  public FileChannel getChannel()

  Returns the unique FileChannel object associated with this file input stream.

  The initial position of the returned channel will be equal to the number of bytes read from the file so far. Reading bytes from this stream will increment the channel's position. Changing the channel's position, either explicitly or by reading, will change this stream's file position.

  Returns:

  the file channel associated with this file input stream

  Since:

  1.4

• finalize

  protected void finalize()
                   throws IOException

  Ensures that the close method of this file input stream is called when there are no more references to it.

  Overrides:

  finalize in class Object

  Throws:

  IOException - if an I/O error occurs.

  See Also:

  close()