- All Implemented Interfaces:
Closeable,AutoCloseable
FileInputStream obtains input bytes
from a file in a file system. What files
are available depends on the host environment.
FileInputStream is meant for reading streams of raw bytes
such as image data. For reading streams of characters, consider using
FileReader.
- API Note:
- The
close()method should be called to release resources used by this stream, either directly, or with thetry-with-resources statement. - Implementation Requirements:
- Subclasses are responsible for the cleanup of resources acquired by the subclass.
Subclasses requiring that resource cleanup take place after a stream becomes
unreachable should use
Cleaneror some other mechanism. - Since:
- 1.0
- See Also:
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Constructor Summary
ConstructorsConstructorDescriptionFileInputStream(File file) Creates aFileInputStreamby opening a connection to an actual file, the file named by theFileobjectfilein the file system.FileInputStream(FileDescriptor fdObj) Creates aFileInputStreamby using the file descriptorfdObj, which represents an existing connection to an actual file in the file system.FileInputStream(String name) Creates aFileInputStreamby opening a connection to an actual file, the file named by the path namenamein the file system. -
Method Summary
Modifier and TypeMethodDescriptionintReturns 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.voidclose()Closes this file input stream and releases any system resources associated with the stream.Returns the uniqueFileChannelobject associated with this file input stream.final FileDescriptorgetFD()Returns theFileDescriptorobject that represents the connection to the actual file in the file system being used by thisFileInputStream.intread()Reads a byte of data from this input stream.intread(byte[] b) Reads up tob.lengthbytes of data from this input stream into an array of bytes.intread(byte[] b, int off, int len) Reads up tolenbytes of data from this input stream into an array of bytes.longskip(long n) Skips over and discardsnbytes of data from the input stream.Methods declared in class java.io.InputStream
mark, markSupported, nullInputStream, readAllBytes, readNBytes, readNBytes, reset, skipNBytes, transferTo
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Constructor Details
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FileInputStream
Creates aFileInputStreamby opening a connection to an actual file, the file named by the path namenamein the file system. A newFileDescriptorobject is created to represent this file connection.First, if there is a security manager, its
checkReadmethod is called with thenameargument 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
FileNotFoundExceptionis 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 itscheckReadmethod denies read access to the file.- See Also:
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FileInputStream
Creates aFileInputStreamby opening a connection to an actual file, the file named by theFileobjectfilein the file system. A newFileDescriptorobject is created to represent this file connection.First, if there is a security manager, its
checkReadmethod is called with the path represented by thefileargument 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
FileNotFoundExceptionis 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 itscheckReadmethod denies read access to the file.- See Also:
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FileInputStream
Creates aFileInputStreamby using the file descriptorfdObj, which represents an existing connection to an actual file in the file system.If there is a security manager, its
checkReadmethod is called with the file descriptorfdObjas its argument to see if it's ok to read the file descriptor. If read access is denied to the file descriptor aSecurityExceptionis thrown.If
fdObjis null then aNullPointerExceptionis thrown.This constructor does not throw an exception if
fdObjisinvalid. However, if the methods are invoked on the resulting stream to attempt I/O on the stream, anIOExceptionis thrown.- Parameters:
fdObj- the file descriptor to be opened for reading.- Throws:
SecurityException- if a security manager exists and itscheckReadmethod denies read access to the file descriptor.- See Also:
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Method Details
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read
Reads a byte of data from this input stream. This method blocks if no input is yet available.- Specified by:
readin classInputStream- Returns:
- the next byte of data, or
-1if the end of the file is reached. - Throws:
IOException- if an I/O error occurs.
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read
Reads up tob.lengthbytes of data from this input stream into an array of bytes. This method blocks until some input is available.- Overrides:
readin classInputStream- Parameters:
b- the buffer into which the data is read.- Returns:
- the total number of bytes read into the buffer, or
-1if there is no more data because the end of the file has been reached. - Throws:
IOException- if an I/O error occurs.- See Also:
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read
Reads up tolenbytes of data from this input stream into an array of bytes. Iflenis not zero, the method blocks until some input is available; otherwise, no bytes are read and0is returned.- Overrides:
readin classInputStream- Parameters:
b- the buffer into which the data is read.off- the start offset in arraybat which the data is written.len- the maximum number of bytes to read.- Returns:
- the total number of bytes read into the buffer, or
-1if there is no more data because the end of the stream has been reached. - Throws:
NullPointerException- Ifbisnull.IndexOutOfBoundsException- Ifoffis negative,lenis negative, orlenis greater thanb.length - offIOException- if an I/O error occurs.- See Also:
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skip
Skips over and discardsnbytes of data from the input stream.The
skipmethod may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly0. Ifnis negative, the method will try to skip backwards. In case the backing file does not support backward skip at its current position, anIOExceptionis thrown. The actual number of bytes skipped is returned. If it skips forwards, it returns a positive value. If it skips backwards, it returns a negative value.This method may skip more bytes than what 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:
skipin classInputStream- 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.- See Also:
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available
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. Returns 0 when the file position is beyond EOF. 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:
availablein classInputStream- 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 callingcloseor an I/O error occurs.
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close
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:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Overrides:
closein classInputStream- API Note:
- Overriding
close()to perform cleanup actions is reliable only when called directly or when called by try-with-resources. - Implementation Requirements:
- Subclasses requiring that resource cleanup take place after a stream becomes
unreachable should use the
Cleanermechanism.If this stream has an associated channel then this method will close the channel, which in turn will close this stream. Subclasses that override this method should be prepared to handle possible reentrant invocation.
- Throws:
IOException- if an I/O error occurs.
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getFD
Returns theFileDescriptorobject that represents the connection to the actual file in the file system being used by thisFileInputStream.- Returns:
- the file descriptor object associated with this stream.
- Throws:
IOException- if an I/O error occurs.- See Also:
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getChannel
Returns the uniqueFileChannelobject associated with this file input stream.The initial
positionof 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
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