public abstract class ByteBuffer extends Buffer implements Comparable
This class is provided as part of the JSR 239 NIO Buffer
building block. It is a subset of the
java.nio.ByteBuffer
class in Java(TM) Standard Edition
version 1.4.2. Differences are noted in bold italic.
The class documentation may make reference to classes that are not
present in the building block.
I/O channels, marking and resetting, and read-only buffers
are not supported. Allocation of non-direct byte buffers,
compaction, and duplication are not supported. The
char
, long
, and double
datatypes are not supported. The following methods are omitted:
ByteBuffer allocate(int capacity)
ByteBuffer compact()
ByteBuffer duplicate()
Buffer mark()
Buffer reset()
boolean isReadOnly()
ByteBuffer asReadOnlyBuffer()
CharBuffer asCharBuffer()
LongBuffer asLongBuffer()
DoubleBuffer asDoubleBuffer()
char getChar()
char getChar(int index)
long getLong()
long getLong(int index)
double getDouble()
double getDouble(int index)
ByteBuffer putChar(char value)
ByteBuffer putChar(int index, char value)
ByteBuffer putLong(int index, long value)
ByteBuffer putLong(long value)
ByteBuffer putDouble(double value)
ByteBuffer putDouble(int index, double value)
This class defines six categories of operations upon byte buffers:
Absolute and relative get
and
put
methods that read and write single bytes;
Relative bulk
get
methods that transfer contiguous
sequences of bytes from this buffer into an array;
Relative bulk
put
methods that transfer contiguous
sequences of bytes from a byte array or some other byte buffer
into this buffer;
Absolute and relative get and put methods that read and write values of other primitive types, translating them to and from sequences of bytes in a particular byte order; JSR 239 does not support certain multi-byte get and put methods.
Methods for creating view buffers, which allow a byte buffer to be viewed as a buffer containing values of some other primitive type; and
Methods for compacting, duplicating, and slicing
a byte buffer. JSR 239 does not support compacting and
duplicating buffers.
Byte buffers can be created either by A byte buffer is either direct or non-direct.
Given a direct byte buffer, the Java virtual machine will make a
best effort to perform native I/O operations directly upon it.
That is, it will attempt to avoid copying the buffer's content to
(or from) an intermediate buffer before (or after) each invocation
of one of the underlying operating system's native I/O operations.
A direct byte buffer may be created by invoking the A direct byte buffer may also be created by mapping a region of
a file directly into memory. An implementation of the Java
platform may optionally support the creation of direct byte buffers
from native code via JNI. If an instance of one of these kinds of
buffers refers to an inaccessible region of memory then an attempt
to access that region will not change the buffer's content and will
cause an unspecified exception to be thrown either at the time of
the access or at some later time.
Whether a byte buffer is direct or non-direct may be determined
by invoking its This class defines methods for reading and writing values of
all other primitive types, except boolean,
For access to heterogenous binary data, that is, sequences of
values of different types, this class defines a family of absolute
and relative get and put methods for each type. For
32-bit floating-point values, for example, this class defines:
Corresponding methods are defined for the types char,
short, int, long, and double.
JSR 239 does not define the For access to homogeneous binary data, that is, sequences of
values of the same type, this class defines methods that can create
views of a given byte buffer. A view buffer is
simply another buffer whose content is backed by the byte buffer.
Changes to the byte buffer's content will be visible in the view
buffer, and vice versa; the two buffers' position, limit, and mark
values are independent. The View buffers have three important advantages over the families of
type-specific get and put methods described above:
A view buffer is indexed not in terms of bytes but rather
in terms of the type-specific size of its values; A view buffer provides relative bulk get and
put methods that can transfer contiguous sequences of
values between a buffer and an array or some other buffer of the
same type; and A view buffer is potentially much more efficient because
it will be direct if, and only if, its backing byte buffer is
direct. The byte order of a view buffer is fixed to be that of its byte
buffer at the time that the view is created. Methods in this class that do not otherwise have a value to
return are specified to return the buffer upon which they are
invoked. This allows method invocations to be chained.
The sequence of statements
allocation
,
which allocates space for the buffer's content, or by
wrapping
an existing byte array into a buffer.
Direct vs. non-direct buffers
allocateDirect
factory method of this class. The buffers returned by this method
typically have somewhat higher allocation and deallocation costs
than non-direct buffers. The contents of direct buffers may reside
outside of the normal garbage-collected heap, and so their impact
upon the memory footprint of an application might not be obvious.
It is therefore recommended that direct buffers be allocated
primarily for large, long-lived buffers that are subject to the
underlying system's native I/O operations. In general it is best
to allocate direct buffers only when they yield a measureable gain
in program performance. Certain JSR 239 methods require the
use of direct buffers.
JSR 239 does not support the techniques described in the
remainder of this paragraph.
isDirect
method. This method is provided so that explicit buffer management
can be done in performance-critical code.
Access to binary data
char
, long
, and
double
. Primitive values are translated to
(or from) sequences of bytes according to the buffer's current byte
order, which may be retrieved and modified via the
order
methods. Specific byte orders are represented
by instances of the ByteOrder
class. The initial
order of a byte buffer is always BIG_ENDIAN
. JSR
239 does not support the ByteOrder
class or the
order
methods. The inital order of a byte buffer is
the platform byte order.
float
getFloat()
float getFloat(int index)
void putFloat(float f)
void putFloat(int index, float f)
char
,
long
, or double
methods. The
index parameters of the absolute get and put methods
are in terms of bytes rather than of the type being read or
written.
asFloatBuffer
method, for example, creates an instance of the FloatBuffer
class that is backed by the
byte buffer upon which the method is invoked. Corresponding
view-creation methods are defined for the types char,
short, int, long, and
double. JSR 239 does not define views of type
char
, long
, or
double
.
Invocation chaining
can, for example, be replaced by the single statement
bb.putInt(0xCAFEBABE);
bb.putShort(3);
bb.putShort(45);
bb.putInt(0xCAFEBABE).putShort(3).putShort(45);
Modifier and Type | Method and Description |
---|---|
static ByteBuffer |
allocateDirect(int capacity)
Allocates a new direct byte buffer.
|
byte[] |
array()
Returns the byte array that backs this
buffer (optional operation).
|
int |
arrayOffset()
Returns the offset within this buffer's backing array of the
first element of the buffer (optional
operation).
|
abstract FloatBuffer |
asFloatBuffer()
Creates a view of this byte buffer as a float buffer.
|
abstract IntBuffer |
asIntBuffer()
Creates a view of this byte buffer as an int buffer.
|
abstract ShortBuffer |
asShortBuffer()
Creates a view of this byte buffer as a short buffer.
|
int |
compareTo(java.lang.Object ob)
Compares this buffer to another.
|
boolean |
equals(java.lang.Object ob)
Tells whether or not this buffer is equal to another object.
|
abstract byte |
get()
Relative get method.
|
ByteBuffer |
get(byte[] dst)
Relative bulk get method.
|
ByteBuffer |
get(byte[] dst,
int offset,
int length)
Relative bulk get method.
|
abstract byte |
get(int index)
Absolute get method.
|
abstract float |
getFloat()
Relative get method for reading a float value.
|
abstract float |
getFloat(int index)
Absolute get method for reading a float value.
|
abstract int |
getInt()
Relative get method for reading an int value.
|
abstract int |
getInt(int index)
Absolute get method for reading an int value.
|
abstract short |
getShort()
Relative get method for reading a short value.
|
abstract short |
getShort(int index)
Absolute get method for reading a short value.
|
boolean |
hasArray()
Tells whether or not this buffer is backed by an accessible
byte array.
|
int |
hashCode()
Returns the current hash code of this buffer.
|
abstract boolean |
isDirect()
Tells whether or not this byte buffer is direct.
|
abstract ByteBuffer |
put(byte b)
Relative put method (optional
operation).
|
ByteBuffer |
put(byte[] src)
Relative bulk put method (optional operation).
|
ByteBuffer |
put(byte[] src,
int offset,
int length)
Relative bulk put method (optional
operation).
|
ByteBuffer |
put(ByteBuffer src)
Relative bulk put method (optional
operation).
|
abstract ByteBuffer |
put(int index,
byte b)
Absolute put method (optional operation).
|
abstract ByteBuffer |
putFloat(float value)
Relative put method for writing a float
value (optional operation).
|
abstract ByteBuffer |
putFloat(int index,
float value)
Absolute put method for writing a float
value (optional operation).
|
abstract ByteBuffer |
putInt(int value)
Relative put method for writing an int
value (optional operation).
|
abstract ByteBuffer |
putInt(int index,
int value)
Absolute put method for writing an int
value (optional operation).
|
abstract ByteBuffer |
putShort(int index,
short value)
Absolute put method for writing a short
value (optional operation).
|
abstract ByteBuffer |
putShort(short value)
Relative put method for writing a short
value (optional operation).
|
abstract ByteBuffer |
slice()
Creates a new byte buffer whose content is a shared
subsequence of this buffer's content.
|
java.lang.String |
toString()
Returns a string summarizing the state of this buffer.
|
static ByteBuffer |
wrap(byte[] array)
Wraps a byte array into a buffer.
|
static ByteBuffer |
wrap(byte[] array,
int offset,
int length)
Wraps a byte array into a buffer.
|
public static ByteBuffer allocateDirect(int capacity)
The new buffer's position will be zero, its limit will be its capacity, and its mark will be undefined. Whether or not it has a backing array is unspecified. For JSR 239, the mark is undefined, and no backing array will be present..
capacity
- The new buffer's capacity, in bytes.java.lang.IllegalArgumentException
- If the capacity
is
a negative integer.public static ByteBuffer wrap(byte[] array, int offset, int length)
The new buffer will be backed by the the given byte array;
that is, modifications to the buffer will cause the array to be
modified and vice versa. The new buffer's capacity will be
array.length, its position will be offset,
its limit will be offset + length, and its mark will
be undefined. Its backing
array
will be the given array, and its
array
offset
will be zero.
array
- The array that will back the new bufferoffset
- The offset of the subarray to be used; must be
non-negative and no larger than array.length. The new
buffer's position will be set to this value.length
- The length of the subarray to be used; must be
non-negative and no larger than array.length - offset.
The new buffer's limit will be set to offset + length.java.lang.IndexOutOfBoundsException
- If the preconditions on the
offset and length parameters do not hold.public static ByteBuffer wrap(byte[] array)
The new buffer will be backed by the the given byte array;
that is, modifications to the buffer will cause the array to be
modified and vice versa. The new buffer's capacity and limit
will be array.length, its position will be zero, and
its mark will be undefined. Its backing
array
will be the given array, and its
array
offset
will be zero.
array
- The array that will back this buffer.public abstract ByteBuffer slice()
The content of the new buffer will start at this buffer's current position. Changes to this buffer's content will be visible in the new buffer, and vice versa; the two buffers' position, limit, and mark values will be independent. JSR 239 does not support the mark.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only. JSR 239 does not support the mark or read-only buffers.
public abstract byte get()
BufferUnderflowException
- If the buffer's current
position is not smaller than its limit.public abstract ByteBuffer put(byte b)
Writes the given byte into this buffer at the current position, and then increments the position.
b
- The byte to be written.BufferOverflowException
- If this buffer's current
position is not smaller than its limit.ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.public abstract byte get(int index)
index
- The index from which the byte will be read.java.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit.public abstract ByteBuffer put(int index, byte b)
Writes the given byte into this buffer at the given index.
index
- The index at which the byte will be written.b
- The byte value to be written.java.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit.ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.public ByteBuffer get(byte[] dst, int offset, int length)
This method transfers bytes from this buffer into the
given destination array. If there are fewer bytes
remaining in the buffer than are required to satisfy the
request, that is, if
length > remaining(),
then no bytes are transferred and a BufferUnderflowException
is thrown.
Otherwise, this method copies length bytes from this buffer into the given array, starting at the current position of this buffer and at the given offset in the array. The position of this buffer is then incremented by length.
In other words, an invocation of this method of the form src.get(dst, off, len) has exactly the same effect as the loop
for (int i = off; i < off + len; i++) dst[i] = src.get();except that it first checks that there are sufficient bytes in this buffer and it is potentially much more efficient.
dst
- The array into which bytes are to be written.offset
- The offset within the array of the first
byte to be written; must be non-negative and no larger
than dst.length.length
- The maximum number of bytes to be written
to the given array; must be non-negative and no larger than
dst.length - offset.BufferUnderflowException
- If there are fewer than
length bytes remaining in this buffer.java.lang.IndexOutOfBoundsException
- If the preconditions on the
offset and length parameters do not hold.public ByteBuffer get(byte[] dst)
This method transfers bytes from this buffer into the given destination array. An invocation of this method of the form src.get(a) behaves in exactly the same way as the invocation
src.get(a, 0, a.length)
BufferUnderflowException
- If there are fewer than
dst.length bytes remaining in this buffer.public ByteBuffer put(ByteBuffer src)
This method transfers the bytes remaining in the
given source buffer into this buffer. If there are more
bytes remaining in the source buffer than in this buffer,
that is, if
src.remaining() > remaining(),
then no bytes are transferred and a BufferOverflowException
is thrown.
Otherwise, this method copies n = src.remaining() bytes from the given buffer into this buffer, starting at each buffer's current position. The positions of both buffers are then incremented by n.
In other words, an invocation of this method of the form dst.put(src) has exactly the same effect as the loop
while (src.hasRemaining()) dst.put(src.get());except that it first checks that there is sufficient space in this buffer and it is potentially much more efficient.
src
- The source buffer from which bytes are to be
read; must not be this buffer.BufferOverflowException
- If there is insufficient space
in this buffer for the remaining bytes in the source
buffer.java.lang.IllegalArgumentException
- If the source buffer is this buffer.ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.public ByteBuffer put(byte[] src, int offset, int length)
This method transfers bytes into this buffer from the
given source array. If there are more bytes to be copied
from the array than remain in this buffer, that is, if
length > remaining(),
then no bytes are transferred and a BufferOverflowException
is thrown.
Otherwise, this method copies length bytes from the given array into this buffer, starting at the given offset in the array and at the current position of this buffer. The position of this buffer is then incremented by length.
In other words, an invocation of this method of the form dst.put(src, off, len) has exactly the same effect as the loop
for (int i = off; i < off + len; i++) dst.put(a[i]);except that it first checks that there is sufficient space in this buffer and it is potentially much more efficient.
src
- The array from which bytes are to be read.offset
- The offset within the array of the first
byte to be read; must be non-negative and no larger than
array.length.length
- The number of bytes to be read from the
given array; must be non-negative and no larger than
array.length - offset.BufferOverflowException
- If there is insufficient space
in this buffer.java.lang.IndexOutOfBoundsException
- If the preconditions on the
offset and length parameters do not hold.ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.public final ByteBuffer put(byte[] src)
This method transfers the entire content of the given source byte array into this buffer. An invocation of this method of the form dst.put(a) behaves in exactly the same way as the invocation
dst.put(a, 0, a.length)
BufferOverflowException
- If there is insufficient space
in this buffer.ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.public final boolean hasArray()
If this method returns true then the array
and arrayOffset
methods
may safely be invoked.
public final byte[] array()
Modifications to this buffer's content will cause the returned array's content to be modified, and vice versa.
Invoke the hasArray
method before
invoking this method in order to ensure that this buffer has an
accessible backing array.
ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.UnsupportedOperationException
- If this buffer is not
backed by an accessible array.public final int arrayOffset()
If this buffer is backed by an array then buffer position p corresponds to array index p + arrayOffset().
Invoke the hasArray
method before
invoking this method in order to ensure that this buffer has an
accessible backing array.
ReadOnlyBufferException
- If this buffer is
read-only. JSR 239 does not support read-only buffer or
the ReadOnlyBufferException
class.UnsupportedOperationException
- If this buffer is not
backed by an accessible array.public abstract boolean isDirect()
public java.lang.String toString()
toString
in class java.lang.Object
public int hashCode()
The hash code of a byte buffer depends only upon its remaining elements; that is, upon the elements from position() up to, and including, the element at limit() - 1.
Because buffer hash codes are content-dependent, it is inadvisable to use buffers as keys in hash maps or similar data structures unless it is known that their contents will not change.
hashCode
in class java.lang.Object
public boolean equals(java.lang.Object ob)
Two byte buffers are equal if, and only if,
They have the same element type,
They have the same number of remaining elements, and
The two sequences of remaining elements, considered independently of their starting positions, are pointwise equal.
A byte buffer is not equal to any other type of object.
equals
in class java.lang.Object
ob
- The object to which this buffer is to be compared.public int compareTo(java.lang.Object ob)
Two byte buffers are compared by comparing their sequences of remaining elements lexicographically, without regard to the starting position of each sequence within its corresponding buffer.
A byte buffer is not comparable to any other type of object.
compareTo
in interface Comparable
ob
- the Object to be compared.java.lang.ClassCastException
- If the argument is not a byte buffer.public abstract short getShort()
Reads the next two bytes at this buffer's current position, composing them into a short value according to the current byte order, and then increments the position by two.
BufferUnderflowException
- If there are fewer than two bytes
remaining in this bufferpublic abstract ByteBuffer putShort(short value)
Writes two bytes containing the given short value, in the current byte order, into this buffer at the current position, and then increments the position by two.
value
- The short value to be writtenBufferOverflowException
- If there are fewer than two bytes
remaining in this bufferReadOnlyBufferException
- If this buffer is read-onlypublic abstract short getShort(int index)
Reads two bytes at the given index, composing them into a short value according to the current byte order.
index
- The index from which the bytes will be readjava.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus onepublic abstract ByteBuffer putShort(int index, short value)
Writes two bytes containing the given short value, in the current byte order, into this buffer at the given index.
index
- The index at which the bytes will be writtenvalue
- The short value to be writtenjava.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus oneReadOnlyBufferException
- If this buffer is read-onlypublic abstract ShortBuffer asShortBuffer()
The content of the new buffer will start at this buffer's current position. Changes to this buffer's content will be visible in the new buffer, and vice versa; the two buffers' position, limit, and mark values will be independent. JSR 239 does not support the mark.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer divided by two, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only. JSR 239 does not support the mark or read-only buffers.
public abstract int getInt()
Reads the next four bytes at this buffer's current position, composing them into an int value according to the current byte order, and then increments the position by four.
BufferUnderflowException
- If there are fewer than four bytes
remaining in this bufferpublic abstract ByteBuffer putInt(int value)
Writes four bytes containing the given int value, in the current byte order, into this buffer at the current position, and then increments the position by four.
value
- The int value to be writtenBufferOverflowException
- If there are fewer than four bytes
remaining in this bufferReadOnlyBufferException
- If this buffer is read-onlypublic abstract int getInt(int index)
Reads four bytes at the given index, composing them into a int value according to the current byte order.
index
- The index from which the bytes will be readjava.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threepublic abstract ByteBuffer putInt(int index, int value)
Writes four bytes containing the given int value, in the current byte order, into this buffer at the given index.
index
- The index at which the bytes will be writtenvalue
- The int value to be writtenjava.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threeReadOnlyBufferException
- If this buffer is read-onlypublic abstract IntBuffer asIntBuffer()
The content of the new buffer will start at this buffer's current position. Changes to this buffer's content will be visible in the new buffer, and vice versa; the two buffers' position, limit, and mark values will be independent. JSR 239 does not support the mark.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer divided by four, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only. JSR 239 does not support the mark or read-only buffers.
public abstract float getFloat()
Reads the next four bytes at this buffer's current position, composing them into a float value according to the current byte order, and then increments the position by four.
BufferUnderflowException
- If there are fewer than four bytes
remaining in this bufferpublic abstract ByteBuffer putFloat(float value)
Writes four bytes containing the given float value, in the current byte order, into this buffer at the current position, and then increments the position by four.
value
- The float value to be writtenBufferOverflowException
- If there are fewer than four bytes
remaining in this bufferReadOnlyBufferException
- If this buffer is read-onlypublic abstract float getFloat(int index)
Reads four bytes at the given index, composing them into a float value according to the current byte order.
index
- The index from which the bytes will be readjava.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threepublic abstract ByteBuffer putFloat(int index, float value)
Writes four bytes containing the given float value, in the current byte order, into this buffer at the given index.
index
- The index at which the bytes will be writtenvalue
- The float value to be writtenjava.lang.IndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threeReadOnlyBufferException
- If this buffer is read-onlypublic abstract FloatBuffer asFloatBuffer()
The content of the new buffer will start at this buffer's current position. Changes to this buffer's content will be visible in the new buffer, and vice versa; the two buffers' position, limit, and mark values will be independent. JSR 239 does not support the mark.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer divided by four, and its mark will be undefined. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only. JSR 239 does not support the mark or read-only buffers.
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