Class ByteBuffer
- All Implemented Interfaces:
Comparable<ByteBuffer>
- Direct Known Subclasses:
MappedByteBuffer
This class defines six categories of operations upon byte buffers:
Absolute and relative
get
andput
methods that read and write single bytes;Absolute and relative
bulk get
methods that transfer contiguous sequences of bytes from this buffer into an array;Absolute and 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
andput
methods that read and write values of other primitive types, translating them to and from sequences of bytes in a particular byte order;Methods for creating view buffers, which allow a byte buffer to be viewed as a buffer containing values of some other primitive type; and
A method for
compacting
a byte buffer.
Byte buffers can be created either by allocation
, which allocates space for the buffer's
content, or by wrapping
an
existing byte array into a buffer.
Direct vs. non-direct buffers
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.
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 isDirect
method. This method is provided so
that explicit buffer management can be done in performance-critical code.
Access to binary data
This class defines methods for reading and writing values of all other
primitive types, except boolean
. 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
.
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:
float getFloat()
float getFloat(int index)
ByteBuffer putFloat(float f)
ByteBuffer putFloat(int index, float f)
Corresponding methods are defined for the types char,
short, int, long
, and double
. 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, limit, and mark 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 char, short, int, long
, and double
.
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.
Invocation chaining
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
bb.putInt(0xCAFEBABE);
bb.putShort(3);
bb.putShort(45);
bb.putInt(0xCAFEBABE).putShort(3).putShort(45);
Optional operations
Methods specified as optional operations throw a ReadOnlyBufferException when invoked on a read-only ByteBuffer. The methods array and arrayOffset throw an UnsupportedOperationException if the ByteBuffer is not backed by an accessible byte array (irrespective of whether the ByteBuffer is read-only).-
Method Summary
Modifier and TypeMethodDescriptionfinal ByteBuffer
alignedSlice
(int unitSize) Creates a new byte buffer whose content is a shared and aligned subsequence of this buffer's content.final int
alignmentOffset
(int index, int unitSize) Returns the memory address, pointing to the byte at the given index, modulo the given unit size.static ByteBuffer
allocate
(int capacity) Allocates a new byte buffer.static ByteBuffer
allocateDirect
(int capacity) Allocates a new direct byte buffer.final byte[]
array()
Returns the byte array that backs this buffer (optional operation).final int
Returns the offset within this buffer's backing array of the first element of the buffer (optional operation).abstract CharBuffer
Creates a view of this byte buffer as a char buffer.abstract DoubleBuffer
Creates a view of this byte buffer as a double buffer.abstract FloatBuffer
Creates a view of this byte buffer as a float buffer.abstract IntBuffer
Creates a view of this byte buffer as an int buffer.abstract LongBuffer
Creates a view of this byte buffer as a long buffer.abstract ByteBuffer
Creates a new, read-only byte buffer that shares this buffer's content.abstract ShortBuffer
Creates a view of this byte buffer as a short buffer.clear()
Clears this buffer.abstract ByteBuffer
compact()
Compacts this buffer (optional operation).int
compareTo
(ByteBuffer that) Compares this buffer to another.abstract ByteBuffer
Creates a new byte buffer that shares this buffer's content.boolean
Tells whether or not this buffer is equal to another object.flip()
Flips this buffer.abstract byte
get()
Relative get method.get
(byte[] dst) Relative bulk get method.get
(byte[] dst, int offset, int length) Relative bulk get method.abstract byte
get
(int index) Absolute get method.get
(int index, byte[] dst) Absolute bulk get method.get
(int index, byte[] dst, int offset, int length) Absolute bulk get method.abstract char
getChar()
Relative get method for reading a char value.abstract char
getChar
(int index) Absolute get method for reading a char value.abstract double
Relative get method for reading a double value.abstract double
getDouble
(int index) Absolute get method for reading a double value.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 long
getLong()
Relative get method for reading a long value.abstract long
getLong
(int index) Absolute get method for reading a long 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.final 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.limit
(int newLimit) Sets this buffer's limit.mark()
Sets this buffer's mark at its position.int
mismatch
(ByteBuffer that) Finds and returns the relative index of the first mismatch between this buffer and a given buffer.final ByteOrder
order()
Retrieves this buffer's byte order.final ByteBuffer
Modifies this buffer's byte order.position
(int newPosition) Sets this buffer's position.abstract ByteBuffer
put
(byte b) Relative put method (optional operation).final ByteBuffer
put
(byte[] src) Relative bulk put method (optional operation).put
(byte[] src, int offset, int length) Relative bulk put method (optional operation).abstract ByteBuffer
put
(int index, byte b) Absolute put method (optional operation).put
(int index, byte[] src) Absolute bulk put method (optional operation).put
(int index, byte[] src, int offset, int length) Absolute bulk put method (optional operation).put
(int index, ByteBuffer src, int offset, int length) Absolute bulk put method (optional operation).put
(ByteBuffer src) Relative bulk put method (optional operation).abstract ByteBuffer
putChar
(char value) Relative put method for writing a char value (optional operation).abstract ByteBuffer
putChar
(int index, char value) Absolute put method for writing a char value (optional operation).abstract ByteBuffer
putDouble
(double value) Relative put method for writing a double value (optional operation).abstract ByteBuffer
putDouble
(int index, double value) Absolute put method for writing a double value (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
putLong
(int index, long value) Absolute put method for writing a long value (optional operation).abstract ByteBuffer
putLong
(long value) Relative put method for writing a long 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).reset()
Resets this buffer's position to the previously-marked position.rewind()
Rewinds this buffer.abstract ByteBuffer
slice()
Creates a new byte buffer whose content is a shared subsequence of this buffer's content.abstract ByteBuffer
slice
(int index, int length) Creates a new byte buffer whose content is a shared subsequence of this buffer's content.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.Methods declared in class java.nio.Buffer
capacity, hasRemaining, isReadOnly, limit, position, remaining
-
Method Details
-
allocateDirect
Allocates a new direct byte buffer.The new buffer's position will be zero, its limit will be its capacity, its mark will be undefined, each of its elements will be initialized to zero, and its byte order will be
BIG_ENDIAN
. Whether or not it has abacking array
is unspecified.- Parameters:
capacity
- The new buffer's capacity, in bytes- Returns:
- The new byte buffer
- Throws:
IllegalArgumentException
- If thecapacity
is a negative integer
-
allocate
Allocates a new byte buffer.The new buffer's position will be zero, its limit will be its capacity, its mark will be undefined, each of its elements will be initialized to zero, and its byte order will be
BIG_ENDIAN
. It will have abacking array
, and itsarray offset
will be zero.- Parameters:
capacity
- The new buffer's capacity, in bytes- Returns:
- The new byte buffer
- Throws:
IllegalArgumentException
- If thecapacity
is a negative integer
-
wrap
Wraps a byte array into a buffer.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 beoffset
, its limit will beoffset + length
, its mark will be undefined, and its byte order will beBIG_ENDIAN
. Itsbacking array
will be the given array, and itsarray offset
will be zero.- Parameters:
array
- The array that will back the new bufferoffset
- The offset of the subarray to be used; must be non-negative and no larger thanarray.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 thanarray.length - offset
. The new buffer's limit will be set tooffset + length
.- Returns:
- The new byte buffer
- Throws:
IndexOutOfBoundsException
- If the preconditions on theoffset
andlength
parameters do not hold
-
wrap
Wraps a byte array into a buffer.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 mark will be undefined, and its byte order will beBIG_ENDIAN
. Itsbacking array
will be the given array, and itsarray offset
will be zero.- Parameters:
array
- The array that will back this buffer- Returns:
- The new byte buffer
-
slice
Creates a new byte buffer whose content is a shared subsequence of this buffer's content.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.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer, its mark will be undefined, and its byte order will be
BIG_ENDIAN
. 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. -
slice
Creates a new byte buffer whose content is a shared subsequence of this buffer's content.The content of the new buffer will start at position
index
in this buffer, and will containlength
elements. 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.The new buffer's position will be zero, its capacity and its limit will be
length
, its mark will be undefined, and its byte order will beBIG_ENDIAN
. 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.- Specified by:
slice
in classBuffer
- Parameters:
index
- The position in this buffer at which the content of the new buffer will start; must be non-negative and no larger thanlimit()
length
- The number of elements the new buffer will contain; must be non-negative and no larger thanlimit() - index
- Returns:
- The new buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or greater thanlimit()
,length
is negative, orlength > limit() - index
- Since:
- 13
-
duplicate
Creates a new byte buffer that shares this buffer's content.The content of the new buffer will be that of this buffer. 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.
The new buffer's capacity, limit, position, and mark values will be identical to those of this buffer, and its byte order will be
BIG_ENDIAN
. 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. -
asReadOnlyBuffer
Creates a new, read-only byte buffer that shares this buffer's content.The content of the new buffer will be that of this buffer. Changes to this buffer's content will be visible in the new buffer; the new buffer itself, however, will be read-only and will not allow the shared content to be modified. The two buffers' position, limit, and mark values will be independent.
The new buffer's capacity, limit, position, and mark values will be identical to those of this buffer, and its byte order will be
BIG_ENDIAN
.If this buffer is itself read-only then this method behaves in exactly the same way as the
duplicate
method.- Returns:
- The new, read-only byte buffer
-
get
public abstract byte get()Relative get method. Reads the byte at this buffer's current position, and then increments the position.- Returns:
- The byte at the buffer's current position
- Throws:
BufferUnderflowException
- If the buffer's current position is not smaller than its limit
-
put
Relative put method (optional operation).Writes the given byte into this buffer at the current position, and then increments the position.
- Parameters:
b
- The byte to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If this buffer's current position is not smaller than its limitReadOnlyBufferException
- If this buffer is read-only
-
get
public abstract byte get(int index) Absolute get method. Reads the byte at the given index.- Parameters:
index
- The index from which the byte will be read- Returns:
- The byte at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit
-
put
Absolute put method (optional operation).Writes the given byte into this buffer at the given index.
- Parameters:
index
- The index at which the byte will be writtenb
- The byte value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limitReadOnlyBufferException
- If this buffer is read-only
-
get
Relative bulk get method.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 aBufferUnderflowException
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 bylength
.In other words, an invocation of this method of the form
src.get(dst, off, len)
has exactly the same effect as the loopfor (int i = off; i < off + len; i++) dst[i] = src.get();
- Parameters:
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 thandst.length
length
- The maximum number of bytes to be written to the given array; must be non-negative and no larger thandst.length - offset
- Returns:
- This buffer
- Throws:
BufferUnderflowException
- If there are fewer thanlength
bytes remaining in this bufferIndexOutOfBoundsException
- If the preconditions on theoffset
andlength
parameters do not hold
-
get
Relative bulk get method.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 invocationsrc.get(a, 0, a.length)
- Parameters:
dst
- The destination array- Returns:
- This buffer
- Throws:
BufferUnderflowException
- If there are fewer thanlength
bytes remaining in this buffer
-
get
Absolute bulk get method.This method transfers
length
bytes from this buffer into the given array, starting at the given index in this buffer and at the given offset in the array. The position of this buffer is unchanged.An invocation of this method of the form
src.get(index, dst, offset, length)
has exactly the same effect as the following loop except that it first checks the consistency of the supplied parameters and it is potentially much more efficient:for (int i = offset, j = index; i < offset + length; i++, j++) dst[i] = src.get(j);
- Parameters:
index
- The index in this buffer from which the first byte will be read; must be non-negative and less thanlimit()
dst
- The destination arrayoffset
- The offset within the array of the first byte to be written; must be non-negative and less thandst.length
length
- The number of bytes to be written to the given array; must be non-negative and no larger than the smaller oflimit() - index
anddst.length - offset
- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- If the preconditions on theindex
,offset
, andlength
parameters do not hold- Since:
- 13
-
get
Absolute bulk get method.This method transfers bytes from this buffer into the given destination array. The position of this buffer is unchanged. An invocation of this method of the form
src.get(index, dst)
behaves in exactly the same way as the invocation:src.get(index, dst, 0, dst.length)
- Parameters:
index
- The index in this buffer from which the first byte will be read; must be non-negative and less thanlimit()
dst
- The destination array- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative, not smaller thanlimit()
, orlimit() - index < dst.length
- Since:
- 13
-
put
Relative bulk put method (optional operation).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 aBufferOverflowException
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 loopwhile (src.hasRemaining()) dst.put(src.get());
- Parameters:
src
- The source buffer from which bytes are to be read; must not be this buffer- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there is insufficient space in this buffer for the remaining bytes in the source bufferIllegalArgumentException
- If the source buffer is this bufferReadOnlyBufferException
- If this buffer is read-only
-
put
Absolute bulk put method (optional operation).This method transfers
length
bytes into this buffer from the given source buffer, starting at the givenoffset
in the source buffer and the givenindex
in this buffer. The positions of both buffers are unchanged.In other words, an invocation of this method of the form
dst.put(index, src, offset, length)
has exactly the same effect as the loopfor (int i = offset, j = index; i < offset + length; i++, j++) dst.put(j, src.get(i));
- Parameters:
index
- The index in this buffer at which the first byte will be written; must be non-negative and less thanlimit()
src
- The buffer from which bytes are to be readoffset
- The index within the source buffer of the first byte to be read; must be non-negative and less thansrc.limit()
length
- The number of bytes to be read from the given buffer; must be non-negative and no larger than the smaller oflimit() - index
andsrc.limit() - offset
- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- If the preconditions on theindex
,offset
, andlength
parameters do not holdReadOnlyBufferException
- If this buffer is read-only- Since:
- 16
-
put
Relative bulk put method (optional operation).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 aBufferOverflowException
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 bylength
.In other words, an invocation of this method of the form
dst.put(src, off, len)
has exactly the same effect as the loopfor (int i = off; i < off + len; i++) dst.put(src[i]);
- Parameters:
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 thansrc.length
length
- The number of bytes to be read from the given array; must be non-negative and no larger thansrc.length - offset
- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there is insufficient space in this bufferIndexOutOfBoundsException
- If the preconditions on theoffset
andlength
parameters do not holdReadOnlyBufferException
- If this buffer is read-only
-
put
Relative bulk put method (optional operation).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 invocationdst.put(a, 0, a.length)
- Parameters:
src
- The source array- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there is insufficient space in this bufferReadOnlyBufferException
- If this buffer is read-only
-
put
Absolute bulk put method (optional operation).This method transfers
length
bytes from the given array, starting at the given offset in the array and at the given index in this buffer. The position of this buffer is unchanged.An invocation of this method of the form
dst.put(index, src, offset, length)
has exactly the same effect as the following loop except that it first checks the consistency of the supplied parameters and it is potentially much more efficient:for (int i = offset, j = index; i < offset + length; i++, j++) dst.put(j, src[i]);
- Parameters:
index
- The index in this buffer at which the first byte will be written; must be non-negative and less thanlimit()
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 less thansrc.length
length
- The number of bytes to be read from the given array; must be non-negative and no larger than the smaller oflimit() - index
andsrc.length - offset
- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- If the preconditions on theindex
,offset
, andlength
parameters do not holdReadOnlyBufferException
- If this buffer is read-only- Since:
- 13
-
put
Absolute bulk put method (optional operation).This method copies bytes into this buffer from the given source array. The position of this buffer is unchanged. An invocation of this method of the form
dst.put(index, src)
behaves in exactly the same way as the invocation:dst.put(index, src, 0, src.length);
- Parameters:
index
- The index in this buffer at which the first byte will be written; must be non-negative and less thanlimit()
src
- The array from which bytes are to be read- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative, not smaller thanlimit()
, orlimit() - index < src.length
ReadOnlyBufferException
- If this buffer is read-only- Since:
- 13
-
hasArray
public final boolean hasArray()Tells whether or not this buffer is backed by an accessible byte array.If this method returns
true
then thearray
andarrayOffset
methods may safely be invoked. -
array
public final byte[] array()Returns the byte array that backs this buffer (optional operation).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.- Specified by:
array
in classBuffer
- Returns:
- The array that backs this buffer
- Throws:
ReadOnlyBufferException
- If this buffer is backed by an array but is read-onlyUnsupportedOperationException
- If this buffer is not backed by an accessible array
-
arrayOffset
public final int arrayOffset()Returns the offset within this buffer's backing array of the first element of the buffer (optional operation).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.- Specified by:
arrayOffset
in classBuffer
- Returns:
- The offset within this buffer's array of the first element of the buffer
- Throws:
ReadOnlyBufferException
- If this buffer is backed by an array but is read-onlyUnsupportedOperationException
- If this buffer is not backed by an accessible array
-
position
Sets this buffer's position. If the mark is defined and larger than the new position then it is discarded. -
limit
Sets this buffer's limit. If the position is larger than the new limit then it is set to the new limit. If the mark is defined and larger than the new limit then it is discarded. -
mark
Sets this buffer's mark at its position. -
reset
Resets this buffer's position to the previously-marked position.Invoking this method neither changes nor discards the mark's value.
-
clear
Clears this buffer. The position is set to zero, the limit is set to the capacity, and the mark is discarded.Invoke this method before using a sequence of channel-read or put operations to fill this buffer. For example:
buf.clear(); // Prepare buffer for reading in.read(buf); // Read data
This method does not actually erase the data in the buffer, but it is named as if it did because it will most often be used in situations in which that might as well be the case.
-
flip
Flips this buffer. The limit is set to the current position and then the position is set to zero. If the mark is defined then it is discarded.After a sequence of channel-read or put operations, invoke this method to prepare for a sequence of channel-write or relative get operations. For example:
buf.put(magic); // Prepend header in.read(buf); // Read data into rest of buffer buf.flip(); // Flip buffer out.write(buf); // Write header + data to channel
This method is often used in conjunction with the
compact
method when transferring data from one place to another. -
rewind
Rewinds this buffer. The position is set to zero and the mark is discarded.Invoke this method before a sequence of channel-write or get operations, assuming that the limit has already been set appropriately. For example:
out.write(buf); // Write remaining data buf.rewind(); // Rewind buffer buf.get(array); // Copy data into array
-
compact
Compacts this buffer (optional operation).The bytes between the buffer's current position and its limit, if any, are copied to the beginning of the buffer. That is, the byte at index p =
position()
is copied to index zero, the byte at index p + 1 is copied to index one, and so forth until the byte at indexlimit()
- 1 is copied to index n =limit()
-1
- p. The buffer's position is then set to n+1 and its limit is set to its capacity. The mark, if defined, is discarded.The buffer's position is set to the number of bytes copied, rather than to zero, so that an invocation of this method can be followed immediately by an invocation of another relative put method.
Invoke this method after writing data from a buffer in case the write was incomplete. The following loop, for example, copies bytes from one channel to another via the buffer
buf
:buf.clear(); // Prepare buffer for use while (in.read(buf) >= 0 || buf.position != 0) { buf.flip(); out.write(buf); buf.compact(); // In case of partial write }
- Returns:
- This buffer
- Throws:
ReadOnlyBufferException
- If this buffer is read-only
-
isDirect
-
toString
-
hashCode
public int hashCode()Returns the current hash code of this buffer.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 atlimit()
-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.
-
equals
Tells whether or not this buffer is equal to another object.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.
-
compareTo
Compares this buffer to another.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. Pairs of
byte
elements are compared as if by invokingByte.compare(byte,byte)
.A byte buffer is not comparable to any other type of object.
- Specified by:
compareTo
in interfaceComparable<ByteBuffer>
- Parameters:
that
- the object to be compared.- Returns:
- A negative integer, zero, or a positive integer as this buffer is less than, equal to, or greater than the given buffer
-
mismatch
Finds and returns the relative index of the first mismatch between this buffer and a given buffer. The index is relative to theposition
of each buffer and will be in the range of 0 (inclusive) up to the smaller of theremaining
elements in each buffer (exclusive).If the two buffers share a common prefix then the returned index is the length of the common prefix and it follows that there is a mismatch between the two buffers at that index within the respective buffers. If one buffer is a proper prefix of the other then the returned index is the smaller of the remaining elements in each buffer, and it follows that the index is only valid for the buffer with the larger number of remaining elements. Otherwise, there is no mismatch.
- Parameters:
that
- The byte buffer to be tested for a mismatch with this buffer- Returns:
- The relative index of the first mismatch between this and the given buffer, otherwise -1 if no mismatch.
- Since:
- 11
-
order
Retrieves this buffer's byte 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
.- Returns:
- This buffer's byte order
-
order
Modifies this buffer's byte order.- Parameters:
bo
- The new byte order, eitherBIG_ENDIAN
orLITTLE_ENDIAN
- Returns:
- This buffer
-
alignmentOffset
public final int alignmentOffset(int index, int unitSize) Returns the memory address, pointing to the byte at the given index, modulo the given unit size.The return value is non-negative in the range of
0
(inclusive) up tounitSize
(exclusive), with zero indicating that the address of the byte at the index is aligned for the unit size, and a positive value that the address is misaligned for the unit size. If the address of the byte at the index is misaligned, the return value represents how much the index should be adjusted to locate a byte at an aligned address. Specifically, the index should either be decremented by the return value if the latter is not greater thanindex
, or be incremented by the unit size minus the return value. Therefore givenint value = alignmentOffset(index, unitSize)
alignmentOffset(index - value, unitSize) == 0, value <= index
alignmentOffset(index + (unitSize - value), unitSize) == 0
- API Note:
- This method may be utilized to determine if unit size bytes from an index can be accessed atomically, if supported by the native platform.
- Parameters:
index
- The index to query for alignment offset, must be non-negative, no upper bounds check is performedunitSize
- The unit size in bytes, must be a power of2
- Returns:
- The indexed byte's memory address modulo the unit size
- Throws:
IllegalArgumentException
- If the index is negative or the unit size is not a power of2
UnsupportedOperationException
- If the buffer is non-direct, andunitSize > 1
- Since:
- 9
- See Also:
-
alignedSlice
Creates a new byte buffer whose content is a shared and aligned subsequence of this buffer's content.The content of the new buffer will start at this buffer's current position rounded up to the index of the nearest aligned byte for the given unit size, and end at this buffer's limit rounded down to the index of the nearest aligned byte for the given unit size. If rounding results in out-of-bound values then the new buffer's capacity and limit will be zero. If rounding is within bounds the following expressions will be true for a new buffer
nb
and unit sizeunitSize
:nb.alignmentOffset(0, unitSize) == 0 nb.alignmentOffset(nb.limit(), unitSize) == 0
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.
The new buffer's position will be zero, its capacity and its limit will be the number of bytes remaining in this buffer or fewer subject to alignment, its mark will be undefined, and its byte order will be
BIG_ENDIAN
. 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.- API Note:
- This method may be utilized to create a new buffer where unit size bytes from index, that is a multiple of the unit size, may be accessed atomically, if supported by the native platform.
- Parameters:
unitSize
- The unit size in bytes, must be a power of2
- Returns:
- The new byte buffer
- Throws:
IllegalArgumentException
- If the unit size not a power of2
UnsupportedOperationException
- If the buffer is non-direct, andunitSize > 1
- Since:
- 9
- See Also:
-
getChar
public abstract char getChar()Relative get method for reading a char value.Reads the next two bytes at this buffer's current position, composing them into a char value according to the current byte order, and then increments the position by two.
- Returns:
- The char value at the buffer's current position
- Throws:
BufferUnderflowException
- If there are fewer than two bytes remaining in this buffer
-
putChar
Relative put method for writing a char value (optional operation).Writes two bytes containing the given char value, in the current byte order, into this buffer at the current position, and then increments the position by two.
- Parameters:
value
- The char value to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there are fewer than two bytes remaining in this bufferReadOnlyBufferException
- If this buffer is read-only
-
getChar
public abstract char getChar(int index) Absolute get method for reading a char value.Reads two bytes at the given index, composing them into a char value according to the current byte order.
- Parameters:
index
- The index from which the bytes will be read- Returns:
- The char value at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus one
-
putChar
Absolute put method for writing a char value (optional operation).Writes two bytes containing the given char value, in the current byte order, into this buffer at the given index.
- Parameters:
index
- The index at which the bytes will be writtenvalue
- The char value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus oneReadOnlyBufferException
- If this buffer is read-only
-
asCharBuffer
Creates a view of this byte buffer as a char buffer.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.
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, its mark will be undefined, and its byte order will be that of the byte buffer at the moment the view is created. 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.
- Returns:
- A new char buffer
-
getShort
public abstract short getShort()Relative get method for reading a short value.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.
- Returns:
- The short value at the buffer's current position
- Throws:
BufferUnderflowException
- If there are fewer than two bytes remaining in this buffer
-
putShort
Relative put method for writing a short value (optional operation).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.
- Parameters:
value
- The short value to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there are fewer than two bytes remaining in this bufferReadOnlyBufferException
- If this buffer is read-only
-
getShort
public abstract short getShort(int index) Absolute get method for reading a short value.Reads two bytes at the given index, composing them into a short value according to the current byte order.
- Parameters:
index
- The index from which the bytes will be read- Returns:
- The short value at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus one
-
putShort
Absolute put method for writing a short value (optional operation).Writes two bytes containing the given short value, in the current byte order, into this buffer at the given index.
- Parameters:
index
- The index at which the bytes will be writtenvalue
- The short value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus oneReadOnlyBufferException
- If this buffer is read-only
-
asShortBuffer
Creates a view of this byte buffer as a short buffer.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.
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, its mark will be undefined, and its byte order will be that of the byte buffer at the moment the view is created. 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.
- Returns:
- A new short buffer
-
getInt
public abstract int getInt()Relative get method for reading an int value.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.
- Returns:
- The int value at the buffer's current position
- Throws:
BufferUnderflowException
- If there are fewer than four bytes remaining in this buffer
-
putInt
Relative put method for writing an int value (optional operation).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.
- Parameters:
value
- The int value to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there are fewer than four bytes remaining in this bufferReadOnlyBufferException
- If this buffer is read-only
-
getInt
public abstract int getInt(int index) Absolute get method for reading an int value.Reads four bytes at the given index, composing them into a int value according to the current byte order.
- Parameters:
index
- The index from which the bytes will be read- Returns:
- The int value at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus three
-
putInt
Absolute put method for writing an int value (optional operation).Writes four bytes containing the given int value, in the current byte order, into this buffer at the given index.
- Parameters:
index
- The index at which the bytes will be writtenvalue
- The int value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus threeReadOnlyBufferException
- If this buffer is read-only
-
asIntBuffer
Creates a view of this byte buffer as an int buffer.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.
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, its mark will be undefined, and its byte order will be that of the byte buffer at the moment the view is created. 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.
- Returns:
- A new int buffer
-
getLong
public abstract long getLong()Relative get method for reading a long value.Reads the next eight bytes at this buffer's current position, composing them into a long value according to the current byte order, and then increments the position by eight.
- Returns:
- The long value at the buffer's current position
- Throws:
BufferUnderflowException
- If there are fewer than eight bytes remaining in this buffer
-
putLong
Relative put method for writing a long value (optional operation).Writes eight bytes containing the given long value, in the current byte order, into this buffer at the current position, and then increments the position by eight.
- Parameters:
value
- The long value to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there are fewer than eight bytes remaining in this bufferReadOnlyBufferException
- If this buffer is read-only
-
getLong
public abstract long getLong(int index) Absolute get method for reading a long value.Reads eight bytes at the given index, composing them into a long value according to the current byte order.
- Parameters:
index
- The index from which the bytes will be read- Returns:
- The long value at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus seven
-
putLong
Absolute put method for writing a long value (optional operation).Writes eight bytes containing the given long value, in the current byte order, into this buffer at the given index.
- Parameters:
index
- The index at which the bytes will be writtenvalue
- The long value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus sevenReadOnlyBufferException
- If this buffer is read-only
-
asLongBuffer
Creates a view of this byte buffer as a long buffer.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.
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 eight, its mark will be undefined, and its byte order will be that of the byte buffer at the moment the view is created. 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.
- Returns:
- A new long buffer
-
getFloat
public abstract float getFloat()Relative get method for reading a float value.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.
- Returns:
- The float value at the buffer's current position
- Throws:
BufferUnderflowException
- If there are fewer than four bytes remaining in this buffer
-
putFloat
Relative put method for writing a float value (optional operation).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.
- Parameters:
value
- The float value to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there are fewer than four bytes remaining in this bufferReadOnlyBufferException
- If this buffer is read-only
-
getFloat
public abstract float getFloat(int index) Absolute get method for reading a float value.Reads four bytes at the given index, composing them into a float value according to the current byte order.
- Parameters:
index
- The index from which the bytes will be read- Returns:
- The float value at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus three
-
putFloat
Absolute put method for writing a float value (optional operation).Writes four bytes containing the given float value, in the current byte order, into this buffer at the given index.
- Parameters:
index
- The index at which the bytes will be writtenvalue
- The float value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus threeReadOnlyBufferException
- If this buffer is read-only
-
asFloatBuffer
Creates a view of this byte buffer as a float buffer.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.
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, its mark will be undefined, and its byte order will be that of the byte buffer at the moment the view is created. 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.
- Returns:
- A new float buffer
-
getDouble
public abstract double getDouble()Relative get method for reading a double value.Reads the next eight bytes at this buffer's current position, composing them into a double value according to the current byte order, and then increments the position by eight.
- Returns:
- The double value at the buffer's current position
- Throws:
BufferUnderflowException
- If there are fewer than eight bytes remaining in this buffer
-
putDouble
Relative put method for writing a double value (optional operation).Writes eight bytes containing the given double value, in the current byte order, into this buffer at the current position, and then increments the position by eight.
- Parameters:
value
- The double value to be written- Returns:
- This buffer
- Throws:
BufferOverflowException
- If there are fewer than eight bytes remaining in this bufferReadOnlyBufferException
- If this buffer is read-only
-
getDouble
public abstract double getDouble(int index) Absolute get method for reading a double value.Reads eight bytes at the given index, composing them into a double value according to the current byte order.
- Parameters:
index
- The index from which the bytes will be read- Returns:
- The double value at the given index
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus seven
-
putDouble
Absolute put method for writing a double value (optional operation).Writes eight bytes containing the given double value, in the current byte order, into this buffer at the given index.
- Parameters:
index
- The index at which the bytes will be writtenvalue
- The double value to be written- Returns:
- This buffer
- Throws:
IndexOutOfBoundsException
- Ifindex
is negative or not smaller than the buffer's limit, minus sevenReadOnlyBufferException
- If this buffer is read-only
-
asDoubleBuffer
Creates a view of this byte buffer as a double buffer.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.
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 eight, its mark will be undefined, and its byte order will be that of the byte buffer at the moment the view is created. 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.
- Returns:
- A new double buffer
-