java.nio
Class DoubleBuffer

java.lang.Object
  |
  +--java.nio.Buffer
        |
        +--java.nio.DoubleBuffer

All Implemented Interfaces:

Comparable

public abstract class DoubleBuffer

extends Buffer

implements Comparable

A double buffer.

This class defines four categories of operations upon double buffers:

• Absolute and relative get and put methods that read and write single doubles;

• Relative bulk get methods that transfer contiguous sequences of doubles from this buffer into an array; and

• Relative bulk put methods that transfer contiguous sequences of doubles from a double array or some other double buffer into this buffer; and

• Methods for compacting, duplicating, and slicing a double buffer.

Double buffers can be created either by allocation, which allocates space for the buffer's content, by wrapping an existing double array into a buffer, or by creating a view of an existing byte buffer

Like a byte buffer, a double buffer is either direct or non-direct. A double buffer created via the wrap methods of this class will be non-direct. A double buffer created as a view of a byte buffer will be direct if, and only if, the byte buffer itself is direct. Whether or not a double buffer is direct may be determined by invoking the isDirect method.

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.

Since:

1.4

Method Summary

static DoubleBuffer	allocate(int capacity) Allocates a new double buffer.
double[]	array() Returns the double 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 DoubleBuffer	asReadOnlyBuffer() Creates a new, read-only double buffer that shares this buffer's content.
abstract DoubleBuffer	compact() Compacts this buffer (optional operation).
int	compareTo(Object ob) Compares this buffer to another object.
abstract DoubleBuffer	duplicate() Creates a new double buffer that shares this buffer's content.
boolean	equals(Object ob) Tells whether or not this buffer is equal to another object.
abstract double	get() Relative get method.
DoubleBuffer	get(double[] dst) Relative bulk get method.
DoubleBuffer	get(double[] dst, int offset, int length) Relative bulk get method.
abstract double	get(int index) Absolute get method.
boolean	hasArray() Tells whether or not this buffer is backed by an accessible double array.
int	hashCode() Returns the current hash code of this buffer.
abstract boolean	isDirect() Tells whether or not this double buffer is direct.
abstract ByteOrder	order() Retrieves this buffer's byte order.
abstract DoubleBuffer	put(double d) Relative put method (optional operation).
DoubleBuffer	put(double[] src) Relative bulk put method (optional operation).
DoubleBuffer	put(double[] src, int offset, int length) Relative bulk put method (optional operation).
DoubleBuffer	put(DoubleBuffer src) Relative bulk put method (optional operation).
abstract DoubleBuffer	put(int index, double d) Absolute put method (optional operation).
abstract DoubleBuffer	slice() Creates a new double buffer whose content is a shared subsequence of this buffer's content.
String	toString() Returns a string summarizing the state of this buffer.
static DoubleBuffer	wrap(double[] array) Wraps a double array into a buffer.
static DoubleBuffer	wrap(double[] array, int offset, int length) Wraps a double array into a buffer.

Methods inherited from class java.nio.Buffer

capacity, clear, flip, hasRemaining, isReadOnly, limit, limit, mark, position, position, remaining, reset, rewind

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

allocate

public static DoubleBuffer allocate(int capacity)

Allocates a new double buffer.

The new buffer's position will be zero, its limit will be its capacity, and its mark will be undefined. It will have a backing array, and its array offset will be zero.

Parameters:

capacity - The new buffer's capacity, in doubles

Returns:

The new double buffer

wrap

public static DoubleBuffer wrap(double[] array,
                                int offset,
                                int length)

Wraps a double array into a buffer.

The new buffer will be backed by the the given double 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.

Parameters:

array - The array that will back the new buffer

offset - 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.

Returns:

The new double buffer

Throws:

IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

wrap

public static DoubleBuffer wrap(double[] array)

Wraps a double array into a buffer.

The new buffer will be backed by the the given double 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.

Parameters:

array - The array that will back this buffer

Returns:

The new double buffer

slice

public abstract DoubleBuffer slice()

Creates a new double 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 doubles 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.

Returns:

The new double buffer

duplicate

public abstract DoubleBuffer duplicate()

Creates a new double 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. 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:

The new double buffer

asReadOnlyBuffer

public abstract DoubleBuffer asReadOnlyBuffer()

Creates a new, read-only double 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.

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 double buffer

get

public abstract double get()

Relative get method. Reads the double at this buffer's current position, and then increments the position.

Returns:

The double at the buffer's current position

Throws:

BufferUnderflowException - If the buffer's current position is not smaller than its limit

put

public abstract DoubleBuffer put(double d)

Relative put method (optional operation).

Writes the given double into this buffer at the current position, and then increments the position.

Parameters:

d - The double to be written

Returns:

This buffer

Throws:

BufferOverflowException - If this buffer's current position is not smaller than its limit

ReadOnlyBufferException - If this buffer is read-only

get

public abstract double get(int index)

Absolute get method. Reads the double at the given index.

Parameters:

index - The index from which the double will be read

Returns:

The double at the given index

Throws:

IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit

put

public abstract DoubleBuffer put(int index,
                                 double d)

Absolute put method (optional operation).

Writes the given double into this buffer at the given index.

Parameters:

index - The index at which the double will be written

d - The double value to be written

Returns:

This buffer

Throws:

IndexOutOfBoundsException - If index is negative or not smaller than the buffer's limit

ReadOnlyBufferException - If this buffer is read-only

get

public DoubleBuffer get(double[] dst,
                        int offset,
                        int length)

Relative bulk get method.

This method transfers doubles from this buffer into the given destination array. If there are fewer doubles remaining in the buffer than are required to satisfy the request, that is, if length > remaining(), then no doubles are transferred and a BufferUnderflowException is thrown.

Otherwise, this method copies length doubles 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 doubles in this buffer and it is potentially much more efficient.

Parameters:

dst - The array into which doubles are to be written

offset - The offset within the array of the first double to be written; must be non-negative and no larger than dst.length

length - The maximum number of doubles to be written to the given array; must be non-negative and no larger than dst.length - offset

Returns:

This buffer

Throws:

BufferUnderflowException - If there are fewer than length doubles remaining in this buffer

IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

get

public DoubleBuffer get(double[] dst)

Relative bulk get method.

This method transfers doubles 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) 

Returns:

This buffer

Throws:

BufferUnderflowException - If there are fewer than length doubles remaining in this buffer

put

public DoubleBuffer put(DoubleBuffer src)

Relative bulk put method (optional operation).

This method transfers the doubles remaining in the given source buffer into this buffer. If there are more doubles remaining in the source buffer than in this buffer, that is, if src.remaining() > remaining(), then no doubles are transferred and a BufferOverflowException is thrown.

Otherwise, this method copies n = src.remaining() doubles 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.

Parameters:

src - The source buffer from which doubles 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 doubles in the source buffer

IllegalArgumentException - If the source buffer is this buffer

ReadOnlyBufferException - If this buffer is read-only

put

public DoubleBuffer put(double[] src,
                        int offset,
                        int length)

Relative bulk put method (optional operation).

This method transfers doubles into this buffer from the given source array. If there are more doubles to be copied from the array than remain in this buffer, that is, if length > remaining(), then no doubles are transferred and a BufferOverflowException is thrown.

Otherwise, this method copies length doubles 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.

Parameters:

offset - The offset within the array of the first double to be read; must be non-negative and no larger than array.length

length - The number of doubles to be read from the given array; must be non-negative and no larger than array.length - offset

Returns:

This buffer

Throws:

BufferOverflowException - If there is insufficient space in this buffer

IndexOutOfBoundsException - If the preconditions on the offset and length parameters do not hold

ReadOnlyBufferException - If this buffer is read-only

put

public final DoubleBuffer put(double[] src)

Relative bulk put method (optional operation).

This method transfers the entire content of the given source double 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) 

Returns:

This buffer

Throws:

BufferOverflowException - If there is insufficient space in this buffer

ReadOnlyBufferException - If this buffer is read-only

hasArray

public final boolean hasArray()

Tells whether or not this buffer is backed by an accessible double array.

If this method returns true then the array and arrayOffset methods may safely be invoked.

Returns:

true if, and only if, this buffer is backed by an array and is not read-only

array

public final double[] array()

Returns the double 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.

Returns:

The array that backs this buffer

Throws:

ReadOnlyBufferException - If this buffer is backed by an array but is read-only

UnsupportedOperationException - 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.

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-only

UnsupportedOperationException - If this buffer is not backed by an accessible array

compact

public abstract DoubleBuffer compact()

Compacts this buffer (optional operation).

The doubles between the buffer's current position and its limit, if any, are copied to the beginning of the buffer. That is, the double at index p = position() is copied to index zero, the double at index p + 1 is copied to index one, and so forth until the double at index limit() - 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 doubles copied, rather than to zero, so that an invocation of this method can be followed immediately by an invocation of another relative put method.

Returns:

This buffer

Throws:

ReadOnlyBufferException - If this buffer is read-only

isDirect

public abstract boolean isDirect()

Tells whether or not this double buffer is direct.

Returns:

true if, and only if, this buffer is direct

toString

public String toString()

Returns a string summarizing the state of this buffer.

Overrides:

toString in class Object

Returns:

A summary string

hashCode

public int hashCode()

Returns the current hash code of this buffer.

The hash code of a double 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.

Overrides:

hashCode in class Object

Returns:

The current hash code of this buffer

See Also:

Object.equals(java.lang.Object), Hashtable

equals

public boolean equals(Object ob)

Tells whether or not this buffer is equal to another object.

Two double buffers are equal if, and only if,

1. They have the same element type,

2. They have the same number of remaining elements, and

3. The two sequences of remaining elements, considered independently of their starting positions, are pointwise equal.

A double buffer is not equal to any other type of object.

Overrides:

equals in class Object

Parameters:

ob - The object to which this buffer is to be compared

Returns:

true if, and only if, this buffer is equal to the given object

See Also:

Object.hashCode(), Hashtable

compareTo

public int compareTo(Object ob)

Compares this buffer to another object.

Two double 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 double buffer is not comparable to any other type of object.

Specified by:

compareTo in interface Comparable

Parameters:

ob - 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

Throws:

ClassCastException - If the argument is not a double buffer

order

public abstract ByteOrder order()

Retrieves this buffer's byte order.

The byte order of a double buffer created by allocation or by wrapping an existing double array is the native order of the underlying hardware. The byte order of a double buffer created as a view of a byte buffer is that of the byte buffer at the moment that the view is created.

Returns:

This buffer's byte order