Java javax.imageio.stream Class MemoryCacheImageOutputStream（JDK8）

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Standard Ed. 8

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java.lang.Object
- javax.imageio.stream.ImageInputStreamImpl
- - javax.imageio.stream.ImageOutputStreamImpl
  - - javax.imageio.stream.MemoryCacheImageOutputStream

All Implemented Interfaces:

Closeable, DataInput, DataOutput, AutoCloseable, ImageInputStream, ImageOutputStream
```
public class MemoryCacheImageOutputStream
extends ImageOutputStreamImpl
```
An implementation of ImageOutputStream that writes its output to a regular OutputStream. A memory buffer is used to cache at least the data between the discard position and the current write position. The only constructor takes an OutputStream, so this class may not be used for read/modify/write operations. Reading can occur only on parts of the stream that have already been written to the cache and not yet flushed.

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

Constructor Summary

Constructors
Constructor and Description
`MemoryCacheImageOutputStream(OutputStream stream)` Constructs a `MemoryCacheImageOutputStream` that will write to a given `OutputStream`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()` Closes this `MemoryCacheImageOutputStream`.
`void`	`flushBefore(long pos)` Discards the initial portion of the stream prior to the indicated position.
`boolean`	`isCached()` Returns `true` since this `ImageOutputStream` caches data in order to allow seeking backwards.
`boolean`	`isCachedFile()` Returns `false` since this `ImageOutputStream` does not maintain a file cache.
`boolean`	`isCachedMemory()` Returns `true` since this `ImageOutputStream` maintains a main memory cache.
`long`	`length()` Returns `-1L` to indicate that the stream has unknown length.
`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`.
`void`	`write(byte[] b, int off, int len)` Writes a sequence of bytes to the stream at the current position.
`void`	`write(int b)` Writes a single byte to the stream at the current position.

Methods inherited from class javax.imageio.stream.ImageOutputStreamImpl
flushBits, write, writeBit, writeBits, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeChars, writeDouble, writeDoubles, writeFloat, writeFloats, writeInt, writeInts, writeLong, writeLongs, writeShort, writeShorts, writeUTF

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl
checkClosed, finalize, flush, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, 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

Methods inherited from interface javax.imageio.stream.ImageInputStream
flush, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, 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

- Constructor Detail
  - MemoryCacheImageOutputStream
```
public MemoryCacheImageOutputStream(OutputStream stream)
```
    Constructs a MemoryCacheImageOutputStream that will write to a given OutputStream.
    
    Parameters:
    
    stream - an OutputStream to write to.
    
    Throws:
    
    IllegalArgumentException - if stream is null.
- 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.
  - write
```
public void write(int b)
           throws IOException
```
    Description copied from interface: ImageOutputStream
    
    Writes a single byte to the stream at the current position. The 24 high-order bits of b are ignored.
    If the bit offset within the stream is non-zero, the remainder of the current byte is padded with 0s and written out first. The bit offset will be 0 after the write. Implementers can use the flushBits method of ImageOutputStreamImpl to guarantee this.
    
    Specified by:
    
    write in interface DataOutput
    
    Specified by:
    
    write in interface ImageOutputStream
    
    Specified by:
    
    write in class ImageOutputStreamImpl
    
    Parameters:
    
    b - an int whose lower 8 bits are to be written.
    
    Throws:
    
    IOException - if an I/O error occurs.
  - write
```
public void write(byte[] b,
                  int off,
                  int len)
           throws IOException
```
    Description copied from interface: ImageOutputStream
    
    Writes a sequence of bytes to the stream at the current position. If len is 0, nothing is written. The byte b[off] is written first, then the byte b[off + 1], and so on.
    If the bit offset within the stream is non-zero, the remainder of the current byte is padded with 0s and written out first. The bit offset will be 0 after the write. Implementers can use the flushBits method of ImageOutputStreamImpl to guarantee this.
    
    Specified by:
    
    write in interface DataOutput
    
    Specified by:
    
    write in interface ImageOutputStream
    
    Specified by:
    
    write in class ImageOutputStreamImpl
    
    Parameters:
    
    b - an array of bytes to be written.
    
    off - the start offset in the data.
    
    len - the number of bytes to write.
    
    Throws:
    
    IOException - if an I/O error occurs.
  - length
```
public long length()
```
    Description copied from class: ImageInputStreamImpl
    
    Returns -1L to indicate that the stream has unknown length. Subclasses must override this method to provide actual length information.
    
    Specified by:
    
    length in interface ImageInputStream
    
    Overrides:
    
    length in class ImageInputStreamImpl
    
    Returns:
    
    -1L to indicate unknown length.
  - isCached
```
public boolean isCached()
```
    Returns true since this ImageOutputStream 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 false since this ImageOutputStream does not maintain a file cache.
    
    Specified by:
    
    isCachedFile in interface ImageInputStream
    
    Overrides:
    
    isCachedFile in class ImageInputStreamImpl
    
    Returns:
    
    false.
    
    See Also:
    
    isCached(), isCachedMemory()
  - isCachedMemory
```
public boolean isCachedMemory()
```
    Returns true since this ImageOutputStream maintains a main memory cache.
    
    Specified by:
    
    isCachedMemory in interface ImageInputStream
    
    Overrides:
    
    isCachedMemory in class ImageInputStreamImpl
    
    Returns:
    
    true.
    
    See Also:
    
    isCached(), isCachedFile()
  - close
```
public void close()
           throws IOException
```
    Closes this MemoryCacheImageOutputStream. All pending data is flushed to the output, and the cache is released. The destination OutputStream 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 I/O error occurs.
  - flushBefore
```
public void flushBefore(long pos)
                 throws IOException
```
    Description copied from interface: ImageInputStream
    
    Discards the initial portion of the stream prior to the indicated position. Attempting to seek to an offset within the flushed portion of the stream will result in an IndexOutOfBoundsException.
    Calling flushBefore may allow classes implementing this interface to free up resources such as memory or disk space that are being used to store data from the stream.
    
    Specified by:
    
    flushBefore in interface ImageInputStream
    
    Specified by:
    
    flushBefore in interface ImageOutputStream
    
    Overrides:
    
    flushBefore in class ImageInputStreamImpl
    
    Parameters:
    
    pos - a long containing the length of the stream prefix that may be flushed.
    
    Throws:
    
    IOException - if an I/O error occurs.

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Java javax.imageio.stream Class MemoryCacheImageOutputStream（JDK8）

Class MemoryCacheImageOutputStream

Field Summary

Fields inherited from class javax.imageio.stream.ImageInputStreamImpl

Constructor Summary

Method Summary

Methods inherited from class javax.imageio.stream.ImageOutputStreamImpl

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl

Methods inherited from class java.lang.Object

Methods inherited from interface javax.imageio.stream.ImageInputStream

Constructor Detail

MemoryCacheImageOutputStream

Method Detail

read

read

write

write

length

isCached

isCachedFile

isCachedMemory

close

flushBefore