Module java.base
Package java.io

Class FileInputStream

  • All Implemented Interfaces:
    Closeable,AutoCloseable
    public classFileInputStreamextendsInputStream
    AFileInputStream 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 usingFileReader.

    API Note:
    To release resources used by this streamclose() 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 asCleaner and remove the overridingfinalize method.
    Implementation Requirements:
    If this FileInputStream has been subclassed and theclose() 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...)

    • Constructor Summary

      Constructors 
      ConstructorDescription
      FileInputStream​(File file)
      Creates aFileInputStream by opening a connection to an actual file, the file named by theFile objectfile in the file system.
      FileInputStream​(FileDescriptor fdObj)
      Creates aFileInputStream by using the file descriptorfdObj, which represents an existing connection to an actual file in the file system.
      FileInputStream​(String name)
      Creates aFileInputStream by opening a connection to an actual file, the file named by the path namename in the file system.

    • Constructor Detail

      • FileInputStream

        public FileInputStream​(String name)                throwsFileNotFoundException
        Creates aFileInputStream by opening a connection to an actual file, the file named by the path namename in the file system. A newFileDescriptor object is created to represent this file connection.

        First, if there is a security manager, itscheckRead method is called with thename argument 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 aFileNotFoundException is 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 itscheckRead method denies read access to the file.
        See Also:
        SecurityManager.checkRead(java.lang.String)

      • FileInputStream

        public FileInputStream​(File file)                throwsFileNotFoundException
        Creates aFileInputStream by opening a connection to an actual file, the file named by theFile objectfile in the file system. A newFileDescriptor object is created to represent this file connection.

        First, if there is a security manager, itscheckRead method is called with the path represented by thefile argument 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 aFileNotFoundException is 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 itscheckRead method denies read access to the file.
        See Also:
        File.getPath(),SecurityManager.checkRead(java.lang.String)

      • FileInputStream

        public FileInputStream​(FileDescriptor fdObj)
        Creates aFileInputStream by using the file descriptorfdObj, which represents an existing connection to an actual file in the file system.

        If there is a security manager, itscheckRead method is called with the file descriptorfdObj as its argument to see if it's ok to read the file descriptor. If read access is denied to the file descriptor aSecurityException is thrown.

        IffdObj is null then aNullPointerException is thrown.

        This constructor does not throw an exception iffdObj isinvalid. However, if the methods are invoked on the resulting stream to attempt I/O on the stream, anIOException is thrown.

        Parameters:
        fdObj - the file descriptor to be opened for reading.
        Throws:
        SecurityException - if a security manager exists and itscheckRead method denies read access to the file descriptor.
        See Also:
        SecurityManager.checkRead(java.io.FileDescriptor)

    • Method Detail

      • read

        public int read()         throwsIOException
        Reads a byte of data from this input stream. This method blocks if no input is yet available.
        Specified by:
        read in class InputStream
        Returns:
        the next byte of data, or-1 if the end of the file is reached.
        Throws:
        IOException - if an I/O error occurs.

      • read

        public int read​(byte[] b)         throwsIOException
        Reads up tob.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.
        Overrides:
        read in class InputStream
        Parameters:
        b - the buffer into which the data is read.
        Returns:
        the total number of bytes read into the buffer, or-1 if 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)

      • read

        public int read​(byte[] b,                int off,                int len)         throwsIOException
        Reads up tolen bytes of data from this input stream into an array of bytes. Iflen is not zero, the method blocks until some input is available; otherwise, no bytes are read and0 is returned.
        Overrides:
        read in class InputStream
        Parameters:
        b - the buffer into which the data is read.
        off - the start offset in the destination arrayb
        len - the maximum number of bytes read.
        Returns:
        the total number of bytes read into the buffer, or-1 if there is no more data because the end of the file has been reached.
        Throws:
        NullPointerException - Ifb isnull.
        IndexOutOfBoundsException - Ifoff is negative,len is negative, orlen is greater thanb.length - off
        IOException - if an I/O error occurs.
        See Also:
        InputStream.read()

      • skip

        public long skip​(long n)          throwsIOException
        Skips over and discardsn bytes of data from the input stream.

        Theskip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly0. Ifn is negative, the method will try to skip backwards. In case the backing file does not support backward skip at its current position, anIOException is 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:
        skip in class InputStream
        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.

      • available

        public int available()              throwsIOException
        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:
        available in class InputStream
        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 callingclose or an I/O error occurs.

      • close

        public void close()           throwsIOException
        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:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        Overrides:
        close in class InputStream
        API Note:
        Overridingclose() 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 asCleaner should be used.
        Throws:
        IOException - if an I/O error occurs.

      • getFD

        public final FileDescriptor getFD()                           throwsIOException
        Returns theFileDescriptor object 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

      • getChannel

        public FileChannel getChannel()
        Returns the uniqueFileChannel object associated with this file input stream.

        The initialposition of 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

      • finalize

        @Deprecated(since="9",forRemoval=true)protected void finalize()                 throwsIOException
        Deprecated, for removal: This API element is subject to removal in a future version.
        Thefinalize method has been deprecated and will be removed. Subclasses that overridefinalize in order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overridingfinalize method. When overriding thefinalize method, 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:
        finalize in class Object
        API Note:
        To release resources used by this streamclose() should be called directly or by try-with-resources.
        Implementation Requirements:
        If this FileInputStream has been subclassed and theclose() 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()