FileInputStreampublic class FileInputStream extends InputStream A 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.
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| Fields Summary |
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| private FileDescriptor | fd | | private FileChannel | channel |
| Constructors Summary |
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public FileInputStream(String name)Creates a FileInputStream by
opening a connection to an actual file,
the file named by the path name name
in the file system. A new FileDescriptor
object is created to represent this file
connection.
First, if there is a security
manager, its checkRead method
is called with the name 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 a
FileNotFoundException is thrown.
this(name != null ? new File(name) : null);
| public FileInputStream(File file)Creates a FileInputStream by
opening a connection to an actual file,
the file named by the File
object file in the file system.
A new FileDescriptor object
is created to represent this file connection.
First, if there is a security manager,
its checkRead method is called
with the path represented by the file
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 a
FileNotFoundException is thrown.
String name = (file != null ? file.getPath() : null);
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(name);
}
if (name == null) {
throw new NullPointerException();
}
fd = new FileDescriptor();
open(name);
| public FileInputStream(FileDescriptor fdObj)Creates a FileInputStream by using the file descriptor
fdObj, which represents an existing connection to an
actual file in the file system.
If there is a security manager, its checkRead method is
called with the file descriptor fdObj as its argument to
see if it's ok to read the file descriptor. If read access is denied
to the file descriptor a SecurityException is thrown.
If fdObj is null then a NullPointerException
is thrown.
SecurityManager security = System.getSecurityManager();
if (fdObj == null) {
throw new NullPointerException();
}
if (security != null) {
security.checkRead(fdObj);
}
fd = fdObj;
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| Methods Summary |
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| public native int | 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. 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.
| | public void | 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.
if (channel != null)
channel.close();
close0();
| | private native void | close0()
| | protected void | finalize()Ensures that the close method of this file input stream is
called when there are no more references to it.
initIDs();
if (fd != null) {
if (fd != fd.in) {
close();
}
}
| | public java.nio.channels.FileChannel | getChannel()Returns the unique {@link java.nio.channels.FileChannel FileChannel}
object associated with this file input stream.
The initial {@link java.nio.channels.FileChannel#position()
position} 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.
synchronized (this) {
if (channel == null)
channel = FileChannelImpl.open(fd, true, false, this);
return channel;
}
| | public final java.io.FileDescriptor | getFD()Returns the FileDescriptor
object that represents the connection to
the actual file in the file system being
used by this FileInputStream.
if (fd != null) return fd;
throw new IOException();
| | private static native void | initIDs()
| | private native void | open(java.lang.String name)Opens the specified file for reading.
| | public native int | read()Reads a byte of data from this input stream. This method blocks
if no input is yet available.
| | public int | read(byte[] b)Reads up to b.length bytes of data from this input
stream into an array of bytes. This method blocks until some input
is available.
return readBytes(b, 0, b.length);
| | public int | read(byte[] b, int off, int len)Reads up to len bytes of data from this input stream
into an array of bytes. If len is not zero, the method
blocks until some input is available; otherwise, no
bytes are read and 0 is returned.
return readBytes(b, off, len);
| | private native int | readBytes(byte[] b, int off, int len)Reads a subarray as a sequence of bytes.
| | public native long | skip(long n)Skips over and discards n bytes of data from the
input stream.
The skip method may, for a variety of
reasons, end up skipping over some smaller number of bytes,
possibly 0. If n is negative, an
IOException is thrown, even though the skip
method of the {@link InputStream} superclass does nothing in this case.
The actual number of bytes skipped is returned.
This method may skip more bytes than 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.
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