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Added in API level 1

FileInputStream

public class FileInputStream
extends InputStream

java.lang.Object
   ↳ java.io.InputStream
     ↳ java.io.FileInputStream
Known Direct Subclasses
Known Indirect Subclasses


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.

See also:

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 estimated number of bytes that can be read or skipped without blocking for more input.

void close()

Closes this 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 a single byte from this stream and returns it as an integer in the range from 0 to 255.

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

Reads up to byteCount bytes from this stream and stores them in the byte array buffer starting at byteOffset.

long skip(long byteCount)

Skips at most byteCount bytes in this stream.

Protected methods

void finalize()

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

Inherited methods

From class java.io.InputStream
From class java.lang.Object
From interface java.io.Closeable
From interface java.lang.AutoCloseable

Public constructors

FileInputStream

Added in API level 1
FileInputStream (File file)

Constructs a new FileInputStream that reads from file.

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

FileInputStream

Added in API level 1
FileInputStream (FileDescriptor fd)

Constructs a new FileInputStream that reads from fd.

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

FileInputStream

Added in API level 1
FileInputStream (String path)

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

Parameters
path String
Throws
FileNotFoundException

Public methods

available

Added in API level 1
int available ()

Returns an estimated number of bytes that can be read or skipped without blocking for more input.

Note that this method provides such a weak guarantee that it is not very useful in practice.

Firstly, the guarantee is "without blocking for more input" rather than "without blocking": a read may still block waiting for I/O to complete — the guarantee is merely that it won't have to wait indefinitely for data to be written. The result of this method should not be used as a license to do I/O on a thread that shouldn't be blocked.

Secondly, the result is a conservative estimate and may be significantly smaller than the actual number of bytes available. In particular, an implementation that always returns 0 would be correct. In general, callers should only use this method if they'd be satisfied with treating the result as a boolean yes or no answer to the question "is there definitely data ready?".

Thirdly, the fact that a given number of bytes is "available" does not guarantee that a read or skip will actually read or skip that many bytes: they may read or skip fewer.

It is particularly important to realize that you must not use this method to size a container and assume that you can read the entirety of the stream without needing to resize the container. Such callers should probably write everything they read to a ByteArrayOutputStream and convert that to a byte array. Alternatively, if you're reading from a file, length() returns the current length of the file (though assuming the file's length can't change may be incorrect, reading a file is inherently racy).

The default implementation of this method in InputStream always returns 0. Subclasses should override this method if they are able to indicate the number of bytes available.

Returns
int the estimated number of bytes available
Throws
IOException

close

Added in API level 1
void close ()

Closes this stream. Concrete implementations of this class should free any resources during close. This implementation does nothing.

Throws
IOException

getChannel

Added in API level 1
FileChannel getChannel ()

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

Returns
FileChannel

getFD

Added in API level 1
FileDescriptor getFD ()

Returns the underlying file descriptor.

Returns
FileDescriptor
Throws
IOException

read

Added in API level 1
int read ()

Reads a single byte from this stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of the stream has been reached. Blocks until one byte has been read, the end of the source stream is detected or an exception is thrown.

Returns
int
Throws
IOException

read

Added in API level 1
int read (byte[] buffer, 
                int byteOffset, 
                int byteCount)

Reads up to byteCount bytes from this stream and stores them in the byte array buffer starting at byteOffset. Returns the number of bytes actually read or -1 if the end of the stream has been reached.

Parameters
buffer byte
byteOffset int
byteCount int
Returns
int
Throws
IOException

skip

Added in API level 1
long skip (long byteCount)

Skips at most byteCount bytes in this stream. The number of actual bytes skipped may be anywhere between 0 and byteCount. If byteCount is negative, this method does nothing and returns 0, but some subclasses may throw.

Note the "at most" in the description of this method: this method may choose to skip fewer bytes than requested. Callers should always check the return value.

This default implementation reads bytes into a temporary buffer. Concrete subclasses should provide their own implementation.

Parameters
byteCount long
Returns
long the number of bytes actually skipped.
Throws
IOException

Protected methods

finalize

Added in API level 1
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.
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