public class FileInputStream extends InputStream implements Closeable
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.
BufferedInputStream,
FileOutputStream| Constructor and Description |
|---|
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)). |
| Modifier and Type | Method and Description |
|---|---|
int |
available()
Returns an estimated number of bytes that can be read or skipped without blocking for more
input.
|
void |
close()
Closes this stream.
|
protected void |
finalize()
Ensures that all resources for this stream are released when it is about
to be garbage collected.
|
FileChannel |
getChannel()
Returns a read-only
FileChannel that shares its position with
this stream. |
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 at most
length bytes from this stream and stores them in
the byte array b starting at offset. |
long |
skip(long byteCount)
Skips at most
n bytes in this stream. |
mark, markSupported, read, resetpublic FileInputStream(File file) throws FileNotFoundException
FileInputStream that reads from file.file - the file from which this stream reads.FileNotFoundException - if file does not exist.public FileInputStream(FileDescriptor fd)
FileInputStream that reads from fd.fd - the FileDescriptor from which this stream reads.NullPointerException - if fd is null.public FileInputStream(String path) throws FileNotFoundException
new FileInputStream(new File(path)).FileNotFoundExceptionpublic int available()
throws IOException
InputStreamNote 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, 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.
available in class InputStreamIOException - if this stream is closed or an error occurspublic void close()
throws IOException
InputStreamclose in interface Closeableclose in interface AutoCloseableclose in class InputStreamIOException - if an error occurs while closing this stream.protected void finalize()
throws IOException
finalize in class ObjectIOException - if an error occurs attempting to finalize this stream.public FileChannel getChannel()
FileChannel that shares its position with
this stream.public final FileDescriptor getFD() throws IOException
IOExceptionpublic int read()
throws IOException
InputStreamread in class InputStreamIOException - if the stream is closed or another IOException occurs.public int read(byte[] buffer,
int byteOffset,
int byteCount)
throws IOException
InputStreamlength bytes from this stream and stores them in
the byte array b starting at offset.read in class InputStreambuffer - the byte array in which to store the bytes read.byteOffset - the initial position in buffer to store the bytes read
from this stream.byteCount - the maximum number of bytes to store in b.IOException - if the stream is closed or another IOException occurs.public long skip(long byteCount)
throws IOException
InputStreamn bytes in this stream. This method does nothing and returns
0 if n is negative, 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.
skip in class InputStreambyteCount - the number of bytes to skip.IOException - if this stream is closed or another IOException occurs.