FileInputStream - JRE Emulation | JRE Emulation
public class

FileInputStream

extends InputStream
java.lang.Object
   ↳ java.io.InputStream
     ↳ java.io.FileInputStream

Class Overview

An input stream that reads bytes from a file.

   File file = ...
   InputStream in = null;
   try {
     in = new BufferedInputStream(new FileInputStream(file));
     ...
   } finally {
     if (in != null) {
       in.close();
     }
   }
 

This stream is not buffered. Most callers should wrap this stream with a BufferedInputStream.

Use FileReader to read characters, as opposed to bytes, from a file.

Summary

Public Constructors
FileInputStream(File file)
Constructs a new FileInputStream that reads from file.
FileInputStream(FileDescriptor fd)
Constructs a new FileInputStream that reads from fd.
FileInputStream(String path)
Equivalent to new FileInputStream(new File(path)).
Public Methods
int available()
Returns an estimate of the number of 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.
void close()
Closes this input stream and releases any system resources associated with the stream.
FileChannel getChannel()
Returns a read-only FileChannel that shares its position with this stream.
final FileDescriptor getFD()
Returns the underlying file descriptor.
int read()
Reads the next byte of data from the input stream.
int read(byte[] buffer, int byteOffset, int byteCount)
Reads up to len bytes of data from the input stream into an array of bytes.
long skip(long byteCount)
Skips over and discards n bytes of data from this input stream.
Protected Methods
void finalize()
Ensures that all resources for this stream are released when it is about to be garbage collected.
Inherited Methods
[Expand]
From class java.io.InputStream
From class java.lang.Object
From interface java.io.Closeable
From interface java.lang.AutoCloseable

Public Constructors

public FileInputStream (File file)

Constructs a new FileInputStream that reads from file.

Parameters
file the file from which this stream reads.
Throws
FileNotFoundException if file does not exist.

public FileInputStream (FileDescriptor fd)

Constructs a new FileInputStream that reads from fd.

Parameters
fd the FileDescriptor from which this stream reads.
Throws
NullPointerException if fd is null.

public FileInputStream (String path)

Equivalent to new FileInputStream(new File(path)).

Public Methods

public int available ()

Returns an estimate of the number of 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.

Note that while some implementations of InputStream will return the total number of bytes in the stream, many will not. It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream.

A subclass' implementation of this method may choose to throw an IOException if this input stream has been closed by invoking the close() method.

The available method for class InputStream always returns 0.

This method should be overridden by subclasses.

Returns
  • an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking or 0 when it reaches the end of the input stream.
Throws
IOException

public void close ()

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

The close method of InputStream does nothing.

Throws
IOException

public FileChannel getChannel ()

Returns a read-only FileChannel that shares its position with this stream.

public final FileDescriptor getFD ()

Returns the underlying file descriptor.

Throws
IOException

public int read ()

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

Returns
  • the next byte of data, or -1 if the end of the stream is reached.
Throws
IOException

public int read (byte[] buffer, int byteOffset, int byteCount)

Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

The read(b, off, len) method for class InputStream simply calls the method read() repeatedly. If the first such call results in an IOException, that exception is returned from the call to the read(b, off, len) method. If any subsequent call to read() results in a IOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned. The default implementation of this method blocks until the requested amount of input data len has been read, end of file is detected, or an exception is thrown. Subclasses are encouraged to provide a more efficient implementation of this method.

Parameters
buffer the buffer into which the data is read.
byteOffset the start offset in array b at which the data is written.
byteCount the maximum number of bytes to read.
Returns
  • the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
Throws
IOException

public long skip (long byteCount)

Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

The skip method of this class creates a byte array and then repeatedly reads into it until n bytes have been read or the end of the stream has been reached. Subclasses are encouraged to provide a more efficient implementation of this method. For instance, the implementation may depend on the ability to seek.

Parameters
byteCount the number of bytes to be skipped.
Returns
  • the actual number of bytes skipped.
Throws
IOException

Protected Methods

protected void finalize ()

Ensures that all resources for this stream are released when it is about to be garbage collected.

Throws
IOException if an error occurs attempting to finalize this stream.