public class ByteBuffer extends Buffer implements Comparable<ByteBuffer>
This class is a subset of the
java.nio.ByteBuffer
class in Java(TM) Standard Edition.
Differences are noted in bold italic.
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 CLDC version of this class is not abstract but a concrete class.
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;
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 slicing
a byte buffer.
Byte buffers can be created by wrapping
an
existing byte array into a buffer.
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 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 measurable gain in program performance.
Whether a byte buffer is direct or non-direct may be determined by
invoking its isDirect
method. This method is provided so
that explicit buffer management can be done in performance-critical code.
For access to heterogeneous 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:
floatgetFloat()
floatgetFloat(int index)
voidputFloat(float f)
voidputFloat(int index, float f)
Corresponding methods are defined for the types short and int. The index parameters of the absolute get and put methods are in terms of bytes rather than of the type being read or written.
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, and limit values are independent. The 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 short, int, and
float.
Views of type
char
, long
, or
double
are not supported.
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
can, for example, be replaced by the single statementbb.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).
|
FloatBuffer |
asFloatBuffer()
Creates a view of this byte buffer as a float buffer.
|
IntBuffer |
asIntBuffer()
Creates a view of this byte buffer as an int buffer.
|
ShortBuffer |
asShortBuffer()
Creates a view of this byte buffer as a short buffer.
|
int |
compareTo(ByteBuffer that)
Compares this buffer to another.
|
boolean |
equals(Object ob)
Tells whether or not this buffer is equal to another object.
|
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.
|
byte |
get(int index)
Absolute get method.
|
float |
getFloat()
Relative get method for reading a float value.
|
float |
getFloat(int index)
Absolute get method for reading a float value.
|
int |
getInt()
Relative get method for reading an int value.
|
int |
getInt(int index)
Absolute get method for reading an int value.
|
short |
getShort()
Relative get method for reading a short value.
|
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.
|
boolean |
isDirect()
Tells whether or not this byte buffer is direct.
|
ByteOrder |
order()
Retrieves this buffer's byte order.
|
ByteBuffer |
order(ByteOrder bo)
Modifies this buffer's byte order.
|
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).
|
ByteBuffer |
put(int index,
byte b)
Absolute put method (optional operation).
|
ByteBuffer |
putFloat(float value)
Relative put method for writing a float
value (optional operation).
|
ByteBuffer |
putFloat(int index,
float value)
Absolute put method for writing a float
value (optional operation).
|
ByteBuffer |
putInt(int value)
Relative put method for writing an int
value (optional operation).
|
ByteBuffer |
putInt(int index,
int value)
Absolute put method for writing an int
value (optional operation).
|
ByteBuffer |
putShort(int index,
short value)
Absolute put method for writing a short
value (optional operation).
|
ByteBuffer |
putShort(short value)
Relative put method for writing a short
value (optional operation).
|
ByteBuffer |
slice()
Creates a new byte buffer whose content is a shared subsequence of
this buffer's content.
|
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. Whether or not it has a
backing array
is unspecified.
capacity
- The new buffer's capacity, in bytesIllegalArgumentException
- If the capacity is a negative integerpublic 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.
UnsupportedOperationException
- If this buffer is not backed by an accessible arraypublic 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.
UnsupportedOperationException
- If this buffer is not backed by an accessible arraypublic 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 and limit values will be independent.
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. The new buffer will be direct if, and only if, this buffer is direct.
public 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 and limit values will be independent.
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. The new buffer will be direct if, and only if, this buffer is direct.
public 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 and limit values will be independent.
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. The new buffer will be direct if, and only if, this buffer is direct.
public int compareTo(ByteBuffer that)
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<ByteBuffer>
that
- The object to which this buffer is to be comparedpublic boolean equals(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 Object
ob
- The object to which this buffer is to be comparedObject.hashCode()
,
HashMap
public byte get()
BufferUnderflowException
- If the buffer's current position is not smaller than its limitpublic 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)
dst
- The array into which bytes are to be writtenBufferUnderflowException
- If there are fewer than length bytes
remaining in this bufferpublic 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 writtenoffset
- The offset within the array of the first byte to be
written; must be non-negative and no larger than
dst.lengthlength
- The maximum number of bytes to be written to the given
array; must be non-negative and no larger than
dst.length - offsetBufferUnderflowException
- If there are fewer than length bytes
remaining in this bufferIndexOutOfBoundsException
- If the preconditions on the offset and length
parameters do not holdpublic byte get(int index)
index
- The index from which the byte will be readIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limitpublic 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 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 readIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threepublic 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 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 readIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threepublic 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 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 readIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus onepublic final boolean hasArray()
If this method returns true then the array
and arrayOffset
methods may safely be invoked.
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 Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public boolean isDirect()
public final ByteOrder order()
The byte order is used when reading or writing multibyte values, and
when creating buffers that are views of this byte buffer. The order of
a newly-created byte buffer is always BIG_ENDIAN
.
public final ByteBuffer order(ByteOrder bo)
bo
- The new byte order,
either BIG_ENDIAN
or LITTLE_ENDIAN
public 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 writtenBufferOverflowException
- If this buffer's current position is not smaller than its limitpublic 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)
src
- The array from which bytes are to be readBufferOverflowException
- If there is insufficient space in this bufferpublic 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 readoffset
- The offset within the array of the first byte to be read;
must be non-negative and no larger than array.lengthlength
- The number of bytes to be read from the given array;
must be non-negative and no larger than
array.length - offsetBufferOverflowException
- If there is insufficient space in this bufferIndexOutOfBoundsException
- If the preconditions on the offset and length
parameters do not holdpublic 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 bufferBufferOverflowException
- If there is insufficient space in this buffer
for the remaining bytes in the source bufferIllegalArgumentException
- If the source buffer is this bufferpublic 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 writtenb
- The byte value to be writtenIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limitpublic 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 bufferpublic 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 writtenIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threepublic 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 bufferpublic 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 writtenIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus threepublic 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 writtenIndexOutOfBoundsException
- If index is negative
or not smaller than the buffer's limit,
minus onepublic 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 bufferpublic 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, and limit values will be independent.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer. The new buffer will be direct if, and only if, this buffer is direct.
public String toString()
public static ByteBuffer wrap(byte[] array)
The new buffer will be backed by 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.
Its backing array
will be the
given array, and its array offset
will
be zero.
array
- The array that will back this bufferpublic static ByteBuffer wrap(byte[] array, int offset, int length)
The new buffer will be backed by 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. 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.IndexOutOfBoundsException
- If the preconditions on the offset and length
parameters do not holdCopyright (c) 2014, Oracle and/or its affiliates. All rights reserved. Use of this specification is subject to license terms.