- java.lang.Object
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- java.io.InputStream
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- java.io.FileInputStream
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- All Implemented Interfaces:
Closeable,AutoCloseable
public class FileInputStream extends InputStream
AFileInputStreamobtains input bytes from a file in a file system. What files are available depends on the host environment.FileInputStreamis meant for reading streams of raw bytes such as image data. For reading streams of characters, consider usingFileReader.- API Note:
- To release resources used by this stream
close()should be called directly or by try-with-resources. Subclasses are responsible for the cleanup of resources acquired by the subclass. Subclasses that overridefinalize()in order to perform cleanup should be modified to use alternative cleanup mechanisms such asCleanerand remove the overridingfinalizemethod. - Implementation Requirements:
- If this FileInputStream has been subclassed and the
close()method has been overridden, theclose()method will be called when the FileInputStream is unreachable. Otherwise, it is implementation specific how the resource cleanup described inclose()is performed. - Since:
- 1.0
- See Also:
File,FileDescriptor,FileOutputStream,Files.newInputStream(java.nio.file.Path, java.nio.file.OpenOption...)
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Constructor Summary
Constructors Constructor Description FileInputStream(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.
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description intavailable()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.voidclose()Closes this file input stream and releases any system resources associated with the stream.protected voidfinalize()Deprecated, for removal: This API element is subject to removal in a future version.Thefinalizemethod has been deprecated and will be removed.FileChannelgetChannel()Returns the uniqueFileChannelobject associated with this file input stream.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, transferTo
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Constructor Detail
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FileInputStream
public FileInputStream(String name) throws FileNotFoundException
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:
SecurityManager.checkRead(java.lang.String)
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FileInputStream
public FileInputStream(File file) throws FileNotFoundException
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:
File.getPath(),SecurityManager.checkRead(java.lang.String)
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FileInputStream
public FileInputStream(FileDescriptor fdObj)
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:
SecurityManager.checkRead(java.io.FileDescriptor)
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Method Detail
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read
public int read() throws IOExceptionReads 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
public int read(byte[] b) throws IOExceptionReads 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:
InputStream.read(byte[], int, int)
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read
public int read(byte[] b, int off, int len) throws IOExceptionReads 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 the destination arrayblen- the maximum number of bytes 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:
NullPointerException- Ifbisnull.IndexOutOfBoundsException- Ifoffis negative,lenis negative, orlenis greater thanb.length - offIOException- if an I/O error occurs.- See Also:
InputStream.read()
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skip
public long skip(long n) throws IOExceptionSkips 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.
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available
public int available() throws IOExceptionReturns 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
public void close() throws IOExceptionCloses 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. Do not depend on finalization to invokeclose; finalization is not reliable and is deprecated. If cleanup of native resources is needed, other mechanisms such as Cleaner should be used. - Throws:
IOException- if an I/O error occurs.
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getFD
public final FileDescriptor getFD() throws IOException
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:
FileDescriptor
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getChannel
public FileChannel 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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finalize
@Deprecated(since="9", forRemoval=true) protected void finalize() throws IOException
Deprecated, for removal: This API element is subject to removal in a future version.Thefinalizemethod has been deprecated and will be removed. Subclasses that overridefinalizein order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overridingfinalizemethod. When overriding thefinalizemethod, its implementation must explicitly ensure thatsuper.finalize()is invoked as described inObject.finalize(). See the specification forObject.finalize()for further information about migration options.Ensures that theclose()method of this file input stream is called when there are no more references to it. Thefinalize()method does not callclose()directly.- Overrides:
finalizein classObject- API Note:
- To release resources used by this stream
close()should be called directly or by try-with-resources. - Implementation Requirements:
- If this FileInputStream has been subclassed and the
close()method has been overridden, theclose()method will be called when the FileInputStream is unreachable. Otherwise, it is implementation specific how the resource cleanup described inclose()is performed. - Throws:
IOException- if an I/O error occurs.- See Also:
close()
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