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java.lang.Object![]()
![]()
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java.nio.charset.CharsetEncoder
public abstract class CharsetEncoder

An engine that can transform a sequence of sixteen-bit Unicode characters into a sequence of
bytes in a specific charset.
The input character sequence is provided in a character buffer or a series
of such buffers. The output byte sequence is written to a byte buffer
or a series of such buffers. An encoder should always be used by making
the following sequence of method invocations, hereinafter referred to as an
encoding operation:
Reset the encoder via the Invoke the Invoke the Invoke the There are two general types of encoding errors. If the input character
sequence is not a legal sixteen-bit Unicode sequence then the input is considered malformed. If
the input character sequence is legal but cannot be mapped to a valid
byte sequence in the given charset then an unmappable character has been encountered.
How an encoding error is handled depends upon the action requested for
that type of error, which is described by an instance of the The default action for malformed-input and unmappable-character errors
is to This class is designed to handle many of the details of the encoding
process, including the implementation of error actions. An encoder for a
specific charset, which is a concrete subclass of this class, need only
implement the abstract Instances of this class are not safe for use by multiple concurrent
threads.
Each invocation of the reset
method, unless it
has not been used before; encode
method zero or more times, as
long as additional input may be available, passing false for the
endOfInput argument and filling the input buffer and flushing the
output buffer between invocations; encode
method one final time, passing
true for the endOfInput argument; and then flush
method so that the encoder can
flush any internal state to the output buffer. encode
method will encode as many
characters as possible from the input buffer, writing the resulting bytes
to the output buffer. The encode
method returns when more
input is required, when there is not enough room in the output buffer, or
when an encoding error has occurred. In each case a CoderResult
object is returned to describe the reason for termination. An invoker can
examine this object and fill the input buffer, flush the output buffer, or
attempt to recover from an encoding error, as appropriate, and try again.
CodingErrorAction
class. The possible error actions are to ignore
the erroneous input, report
the error to the invoker via
the returned CoderResult
object, or replace
the erroneous input with the current value of the
replacement byte array. The replacement
is initially set to the encoder's default replacement, which often
(but not always) has the initial value { (byte)'?' };
its value may be changed via the replaceWith
method.
report
them. The
malformed-input error action may be changed via the onMalformedInput
method; the
unmappable-character action may be changed via the onUnmappableCharacter
method.
encodeLoop
method, which
encapsulates the basic encoding loop. A subclass that maintains internal
state should, additionally, override the flush
and reset
methods.
ByteBuffer
,
CharBuffer
,
Charset
,
CharsetDecoder

| Constructor Summary | |
|---|---|
protected |
CharsetEncoder
Initializes a new encoder. |
protected |
CharsetEncoder
Initializes a new encoder. |
| Method Summary | |
|---|---|
float |
averageBytesPerChar
Returns the average number of bytes that will be produced for each character of input. |
boolean |
canEncode
Tells whether or not this encoder can encode the given character. |
boolean |
canEncode
Tells whether or not this encoder can encode the given character sequence. |
Charset |
charset
Returns the charset that created this encoder. |
ByteBuffer |
encode
Convenience method that encodes the remaining content of a single input character buffer into a newly-allocated byte buffer. |
CoderResult |
encode
Encodes as many characters as possible from the given input buffer, writing the results to the given output buffer. |
protected abstract CoderResult |
encodeLoop
Encodes one or more characters into one or more bytes. |
CoderResult |
flush
Flushes this encoder. |
protected CoderResult |
implFlush
Flushes this encoder. |
protected void |
implOnMalformedInput
Reports a change to this encoder's malformed-input action. |
protected void |
implOnUnmappableCharacter
Reports a change to this encoder's unmappable-character action. |
protected void |
implReplaceWith
Reports a change to this encoder's replacement value. |
protected void |
implReset
Resets this encoder, clearing any charset-specific internal state. |
boolean |
isLegalReplacement
Tells whether or not the given byte array is a legal replacement value for this encoder. |
CodingErrorAction |
malformedInputAction
Returns this encoder's current action for malformed-input errors. |
float |
maxBytesPerChar
Returns the maximum number of bytes that will be produced for each character of input. |
CharsetEncoder |
onMalformedInput
Changes this encoder's action for malformed-input errors. |
CharsetEncoder |
onUnmappableCharacter
Changes this encoder's action for unmappable-character errors. |
byte[] |
replacement
Returns this encoder's replacement value. |
CharsetEncoder |
replaceWith
Changes this encoder's replacement value. |
CharsetEncoder |
reset
Resets this encoder, clearing any internal state. |
CodingErrorAction |
unmappableCharacterAction
Returns this encoder's current action for unmappable-character errors. |
Methods inherited from class java.lang.Object ![]() |
|---|
clone |
| Constructor Detail |
|---|

protected CharsetEncoder(Charset![]()
![]()
cs, float averageBytesPerChar, float maxBytesPerChar, byte[] replacement)
averageBytesPerChar - A positive float value indicating the expected number of
bytes that will be produced for each input charactermaxBytesPerChar - A positive float value indicating the maximum number of
bytes that will be produced for each input characterreplacement - The initial replacement; must not be null, must have
non-zero length, must not be longer than maxBytesPerChar,
and must be legal
IllegalArgumentException

- If the preconditions on the parameters do not hold

protected CharsetEncoder(Charset![]()
![]()
cs, float averageBytesPerChar, float maxBytesPerChar)
averageBytesPerChar - A positive float value indicating the expected number of
bytes that will be produced for each input charactermaxBytesPerChar - A positive float value indicating the maximum number of
bytes that will be produced for each input character
IllegalArgumentException

- If the preconditions on the parameters do not hold| Method Detail |
|---|

public final Charset![]()
![]()
charset()

public final byte[] replacement()

public final CharsetEncoder![]()
![]()
replaceWith(byte[] newReplacement)
This method invokes the implReplaceWith
method, passing the new replacement, after checking that the new
replacement is acceptable.
newReplacement - The new replacement; must not be null, must have
non-zero length, must not be longer than the value returned by
the maxBytesPerChar
method, and
must be legal
IllegalArgumentException

- If the preconditions on the parameter do not hold

protected void implReplaceWith(byte[] newReplacement)
The default implementation of this method does nothing. This method should be overridden by encoders that require notification of changes to the replacement.
newReplacement -

public boolean isLegalReplacement(byte[] repl)
A replacement is legal if, and only if, it is a legal sequence of bytes in this encoder's charset; that is, it must be possible to decode the replacement into one or more sixteen-bit Unicode characters.
The default implementation of this method is not very efficient; it should generally be overridden to improve performance.
repl - The byte array to be tested

public CodingErrorAction![]()
![]()
malformedInputAction()

public final CharsetEncoder![]()
![]()
onMalformedInput(CodingErrorAction
![]()
![]()
newAction)
This method invokes the implOnMalformedInput
method, passing the new action.
newAction - The new action; must not be null
IllegalArgumentException

- If the precondition on the parameter does not hold

protected void implOnMalformedInput(CodingErrorAction![]()
![]()
newAction)
The default implementation of this method does nothing. This method should be overridden by encoders that require notification of changes to the malformed-input action.

public CodingErrorAction![]()
![]()
unmappableCharacterAction()

public final CharsetEncoder![]()
![]()
onUnmappableCharacter(CodingErrorAction
![]()
![]()
newAction)
This method invokes the implOnUnmappableCharacter
method, passing the new action.
newAction - The new action; must not be null
IllegalArgumentException

- If the precondition on the parameter does not hold

protected void implOnUnmappableCharacter(CodingErrorAction![]()
![]()
newAction)
The default implementation of this method does nothing. This method should be overridden by encoders that require notification of changes to the unmappable-character action.

public final float averageBytesPerChar()

public final float maxBytesPerChar()

public final CoderResult![]()
![]()
encode(CharBuffer
![]()
![]()
in, ByteBuffer
![]()
![]()
out, boolean endOfInput)
The buffers are read from, and written to, starting at their current
positions. At most in.remaining()
characters
will be read and at most out.remaining()
bytes will be written. The buffers' positions will be advanced to
reflect the characters read and the bytes written, but their marks and
limits will not be modified.
In addition to reading characters from the input buffer and writing
bytes to the output buffer, this method returns a CoderResult
object to describe its reason for termination:
CoderResult.UNDERFLOW
indicates that as much of the
input buffer as possible has been encoded. If there are no characters
remaining and the invoker has no further input then the encoding
operation is complete. Otherwise there is insufficient input for the
operation to proceed, so this method should be invoked again with
further input.
CoderResult.OVERFLOW
indicates that the output buffer
is full. This method should be invoked again with a non-full output
buffer.
A malformed-input
result indicates that a malformed-input
error has been detected. The malformed characters begin at the input
buffer's (possibly incremented) position; the number of malformed
characters may be determined by invoking the result object's length
method. This case applies only if the
malformed action
of this encoder
is CodingErrorAction.REPORT
; otherwise the malformed input
will be ignored or replaced, as requested.
An unmappable-character
result indicates that an
unmappable-character error has been detected. The characters that
encode the unmappable character begin at the input buffer's (possibly
incremented) position; the number of such characters may be determined
by invoking the result object's length
method. This case applies only if the unmappable action
of this encoder is CodingErrorAction.REPORT
; otherwise the unmappable character will be
ignored or replaced, as requested.
The endOfInput parameter advises this method as to whether the invoker can provide further input beyond that contained in the given input buffer. If there is a possibility of providing additional input then the invoker should pass false for this parameter; if there is no possibility of providing further input then the invoker should pass true. It is not erroneous, and in fact it is quite common, to pass false in one invocation and later discover that no further input was actually available. It is critical, however, that the final invocation of this method in a sequence of invocations always pass true so that any remaining unencoded input will be treated as being malformed.
This method works by invoking the encodeLoop
method, interpreting its results, handling error conditions, and
reinvoking it as necessary.
in - The input character bufferout - The output byte bufferendOfInput - true if, and only if, the invoker can provide no
additional input characters beyond those in the given buffer
IllegalStateException

- If an encoding operation is already in progress and the previous
step was an invocation neither of the reset
method, nor of this method with a value of false for
the endOfInput parameter, nor of this method with a
value of true for the endOfInput parameter
but a return value indicating an incomplete encoding operation
CoderMalfunctionError

- If an invocation of the encodeLoop method threw
an unexpected exception

public final CoderResult![]()
![]()
flush(ByteBuffer
![]()
![]()
out)
Some encoders maintain internal state and may need to write some final bytes to the output buffer once the overall input sequence has been read.
Any additional output is written to the output buffer beginning at
its current position. At most out.remaining()
bytes will be written. The buffer's position will be advanced
appropriately, but its mark and limit will not be modified.
If this method completes successfully then it returns CoderResult.UNDERFLOW
. If there is insufficient room in the output
buffer then it returns CoderResult.OVERFLOW
. If this happens
then this method must be invoked again, with an output buffer that has
more room, in order to complete the current encoding
operation.
This method invokes the implFlush
method to
perform the actual flushing operation.
out - The output byte buffer
CoderResult.UNDERFLOW
or
CoderResult.OVERFLOW
IllegalStateException

- If the previous step of the current encoding operation was an
invocation neither of the reset
method nor of
the three-argument encode
method
with a value of true for the endOfInput
parameter

protected CoderResult![]()
![]()
implFlush(ByteBuffer
![]()
![]()
out)
The default implementation of this method does nothing, and always
returns CoderResult.UNDERFLOW
. This method should be overridden
by encoders that may need to write final bytes to the output buffer
once the entire input sequence has been read.
out - The output byte buffer
CoderResult.UNDERFLOW
or
CoderResult.OVERFLOW


public final CharsetEncoder![]()
![]()
reset()
This method resets charset-independent state and also invokes the
implReset
method in order to perform any
charset-specific reset actions.

protected void implReset()
The default implementation of this method does nothing. This method should be overridden by encoders that maintain internal state.

protected abstract CoderResult![]()
![]()
encodeLoop(CharBuffer
![]()
![]()
in, ByteBuffer
![]()
![]()
out)
This method encapsulates the basic encoding loop, encoding as many
characters as possible until it either runs out of input, runs out of room
in the output buffer, or encounters an encoding error. This method is
invoked by the encode
method, which handles result
interpretation and error recovery.
The buffers are read from, and written to, starting at their current
positions. At most in.remaining()
characters
will be read, and at most out.remaining()
bytes will be written. The buffers' positions will be advanced to
reflect the characters read and the bytes written, but their marks and
limits will not be modified.
This method returns a CoderResult
object to describe its
reason for termination, in the same manner as the encode
method. Most implementations of this method will handle encoding errors
by returning an appropriate result object for interpretation by the
encode
method. An optimized implementation may instead
examine the relevant error action and implement that action itself.
An implementation of this method may perform arbitrary lookahead by
returning CoderResult.UNDERFLOW
until it receives sufficient
input.
in - The input character bufferout - The output byte buffer

public final ByteBuffer![]()
![]()
encode(CharBuffer
![]()
![]()
in) throws CharacterCodingException
![]()
![]()
This method implements an entire encoding operation; that is, it resets this encoder, then it encodes the characters in the given character buffer, and finally it flushes this encoder. This method should therefore not be invoked if an encoding operation is already in progress.
in - The input character buffer
IllegalStateException

- If an encoding operation is already in progress
MalformedInputException

- If the character sequence starting at the input buffer's current
position is not a legal sixteen-bit Unicode sequence and the current malformed-input action
is CodingErrorAction.REPORT
UnmappableCharacterException

- If the character sequence starting at the input buffer's current
position cannot be mapped to an equivalent byte sequence and
the current unmappable-character action is CodingErrorAction.REPORT
CharacterCodingException


public boolean canEncode(char c)
This method returns false if the given character is a
surrogate character; such characters can be interpreted only when they
are members of a pair consisting of a high surrogate followed by a low
surrogate. The canEncode(CharSequence)
method may be used to test whether or not a
character sequence can be encoded.
This method may modify this encoder's state; it should therefore not be invoked if an encoding operation is already in progress.
The default implementation of this method is not very efficient; it should generally be overridden to improve performance.
IllegalStateException

- If an encoding operation is already in progress

public boolean canEncode(CharSequence![]()
![]()
cs)
If this method returns false for a particular character sequence then more information about why the sequence cannot be encoded may be obtained by performing a full encoding operation.
This method may modify this encoder's state; it should therefore not be invoked if an encoding operation is already in progress.
The default implementation of this method is not very efficient; it should generally be overridden to improve performance.
IllegalStateException

- If an encoding operation is already in progress
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