Java javax.imageio.stream Class FileCacheImageInputStream（JDK8）

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Java™ Platform
Standard Ed. 8

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java.lang.Object
- javax.imageio.stream.ImageInputStreamImpl
- - javax.imageio.stream.FileCacheImageInputStream

All Implemented Interfaces:

Closeable, DataInput, AutoCloseable, ImageInputStream
```
public class FileCacheImageInputStream
extends ImageInputStreamImpl
```
An implementation of ImageInputStream that gets its input from a regular InputStream. A file is used to cache previously read data.

Field Summary
- Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
  bitOffset, byteOrder, flushedPos, streamPos

Constructor Summary

Constructors
Constructor and Description
`FileCacheImageInputStream(InputStream stream, File cacheDir)` Constructs a `FileCacheImageInputStream` that will read from a given `InputStream`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()` Closes this `FileCacheImageInputStream`, closing and removing the cache file.
`protected void`	`finalize()` Finalizes this object prior to garbage collection.
`boolean`	`isCached()` Returns `true` since this `ImageInputStream` caches data in order to allow seeking backwards.
`boolean`	`isCachedFile()` Returns `true` since this `ImageInputStream` maintains a file cache.
`boolean`	`isCachedMemory()` Returns `false` since this `ImageInputStream` does not maintain a main memory cache.
`int`	`read()` Reads a single byte from the stream and returns it as an `int` between 0 and 255.
`int`	`read(byte[] b, int off, int len)` Reads up to `len` bytes from the stream, and stores them into `b` starting at index `off`.

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl
checkClosed, flush, flushBefore, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, length, mark, read, readBit, readBits, readBoolean, readByte, readBytes, readChar, readDouble, readFloat, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedInt, readUnsignedShort, readUTF, reset, seek, setBitOffset, setByteOrder, skipBytes, skipBytes

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - FileCacheImageInputStream
```
public FileCacheImageInputStream(InputStream stream,
                                 File cacheDir)
                          throws IOException
```
    Constructs a FileCacheImageInputStream that will read from a given InputStream.
    A temporary file is used as a cache. If cacheDiris non-null and is a directory, the file will be created there. If it is null, the system-dependent default temporary-file directory will be used (see the documentation for File.createTempFile for details).
    
    Parameters:
    
    stream - an InputStream to read from.
    
    cacheDir - a File indicating where the cache file should be created, or null to use the system directory.
    
    Throws:
    
    IllegalArgumentException - if stream is null.
    
    IllegalArgumentException - if cacheDir is non-null but is not a directory.
    
    IOException - if a cache file cannot be created.
- Method Detail
  - read
```
public int read()
         throws IOException
```
    Description copied from class: ImageInputStreamImpl
    
    Reads a single byte from the stream and returns it as an int between 0 and 255. If EOF is reached, -1 is returned.
    Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.
    
    The bit offset within the stream must be reset to zero before the read occurs.
    
    Specified by:
    
    read in interface ImageInputStream
    
    Specified by:
    
    read in class ImageInputStreamImpl
    
    Returns:
    
    the value of the next byte in the stream, or -1 if EOF is reached.
    
    Throws:
    
    IOException - if the stream has been closed.
  - read
```
public int read(byte[] b,
                int off,
                int len)
         throws IOException
```
    Description copied from class: ImageInputStreamImpl
    
    Reads up to len bytes from the stream, and stores them into b starting at index off. If no bytes can be read because the end of the stream has been reached, -1 is returned.
    The bit offset within the stream must be reset to zero before the read occurs.
    
    Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.
    
    Specified by:
    
    read in interface ImageInputStream
    
    Specified by:
    
    read in class ImageInputStreamImpl
    
    Parameters:
    
    b - an array of bytes to be written to.
    
    off - the starting position within b to write to.
    
    len - the maximum number of bytes to read.
    
    Returns:
    
    the number of bytes actually read, or -1 to indicate EOF.
    
    Throws:
    
    IOException - if an I/O error occurs.
  - isCached
```
public boolean isCached()
```
    Returns true since this ImageInputStream caches data in order to allow seeking backwards.
    
    Specified by:
    
    isCached in interface ImageInputStream
    
    Overrides:
    
    isCached in class ImageInputStreamImpl
    
    Returns:
    
    true.
    
    See Also:
    
    isCachedMemory(), isCachedFile()
  - isCachedFile
```
public boolean isCachedFile()
```
    Returns true since this ImageInputStream maintains a file cache.
    
    Specified by:
    
    isCachedFile in interface ImageInputStream
    
    Overrides:
    
    isCachedFile in class ImageInputStreamImpl
    
    Returns:
    
    true.
    
    See Also:
    
    isCached(), isCachedMemory()
  - isCachedMemory
```
public boolean isCachedMemory()
```
    Returns false since this ImageInputStream does not maintain a main memory cache.
    
    Specified by:
    
    isCachedMemory in interface ImageInputStream
    
    Overrides:
    
    isCachedMemory in class ImageInputStreamImpl
    
    Returns:
    
    false.
    
    See Also:
    
    isCached(), isCachedFile()
  - close
```
public void close()
           throws IOException
```
    Closes this FileCacheImageInputStream, closing and removing the cache file. The source InputStream is not closed.
    
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Specified by:
    
    close in interface ImageInputStream
    
    Overrides:
    
    close in class ImageInputStreamImpl
    
    Throws:
    
    IOException - if an error occurs.
  - finalize
```
protected void finalize()
                 throws Throwable
```
    Finalizes this object prior to garbage collection. The close method is called to close any open input source. This method should not be called from application code.
    
    Overrides:
    
    finalize in class ImageInputStreamImpl
    
    Throws:
    
    Throwable - if an error occurs during superclass finalization.
    
    See Also:
    
    WeakReference, PhantomReference

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Java javax.imageio.stream Class FileCacheImageInputStream（JDK8）

Class FileCacheImageInputStream

Field Summary

Fields inherited from class javax.imageio.stream.ImageInputStreamImpl

Constructor Summary

Method Summary

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl

Methods inherited from class java.lang.Object

Constructor Detail

FileCacheImageInputStream

Method Detail

read

read

isCached

isCachedFile

isCachedMemory

close

finalize