SizeSequence
object
efficiently maintains an ordered list
of sizes and corresponding positions.
One situation for which SizeSequence
might be appropriate is in a component
that displays multiple rows of unequal size.
In this case, a single SizeSequence
object could be used to track the heights
and Y positions of all rows.
Another example would be a multicolumn component,
such as a JTable
,
in which the column sizes are not all equal.
The JTable
might use a single
SizeSequence
object
to store the widths and X positions of all the columns.
The JTable
could then use the
SizeSequence
object
to find the column corresponding to a certain position.
The JTable
could update the
SizeSequence
object
whenever one or more column sizes changed.
The following figure shows the relationship between size and position data for a multicolumn component.
In the figure, the first index (0) corresponds to the first column,
the second index (1) to the second column, and so on.
The first column's position starts at 0,
and the column occupies size_{0} pixels,
where size_{0} is the value returned by
getSize(0)
.
Thus, the first column ends at size_{0}  1.
The second column then begins at
the position size_{0}
and occupies size_{1} (getSize(1)
) pixels.
Note that a SizeSequence
object simply represents intervals
along an axis.
In our examples, the intervals represent height or width in pixels.
However, any other unit of measure (for example, time in days)
could be just as valid.
Implementation Notes
Normally when storing the size and position of entries, one would choose between storing the sizes or storing their positions instead. The two common operations that are needed during rendering are:getIndex(position)
and setSize(index, size)
.
Whichever choice of internal format is made one of these
operations is costly when the number of entries becomes large.
If sizes are stored, finding the index of the entry
that encloses a particular position is linear in the
number of entries. If positions are stored instead, setting
the size of an entry at a particular index requires updating
the positions of the affected entries, which is also a linear
calculation.
Like the above techniques this class holds an array of N integers internally but uses a hybrid encoding, which is halfway between the sizebased and positionalbased approaches. The result is a data structure that takes the same space to store the information but can perform most operations in Log(N) time instead of O(N), where N is the number of entries in the list.
Two operations that remain O(N) in the number of entries are
the insertEntries
and removeEntries
methods, both
of which are implemented by converting the internal array to
a set of integer sizes, copying it into the new array, and then
reforming the hybrid representation in place.
 Since:
 1.3

Constructor Summary
ConstructorDescriptionCreates a newSizeSequence
object that contains no entries.SizeSequence
(int numEntries) Creates a newSizeSequence
object that contains the specified number of entries, all initialized to have size 0.SizeSequence
(int[] sizes) Creates a newSizeSequence
object that contains the specified sizes.SizeSequence
(int numEntries, int value) Creates a newSizeSequence
object that contains the specified number of entries, all initialized to have sizevalue
. 
Method Summary
Modifier and TypeMethodDescriptionint
getIndex
(int position) Returns the index of the entry that corresponds to the specified position.int
getPosition
(int index) Returns the start position for the specified entry.int
getSize
(int index) Returns the size of the specified entry.int[]
getSizes()
Returns the size of all entries.void
insertEntries
(int start, int length, int value) Adds a contiguous group of entries to thisSizeSequence
.void
removeEntries
(int start, int length) Removes a contiguous group of entries from thisSizeSequence
.void
setSize
(int index, int size) Sets the size of the specified entry.void
setSizes
(int[] sizes) Resets thisSizeSequence
object, using the data in thesizes
argument.

Constructor Details

SizeSequence
public SizeSequence()Creates a newSizeSequence
object that contains no entries. To add entries, you can useinsertEntries
orsetSizes
. See Also:

SizeSequence
public SizeSequence(int numEntries) Creates a newSizeSequence
object that contains the specified number of entries, all initialized to have size 0. Parameters:
numEntries
 the number of sizes to track Throws:
NegativeArraySizeException
 ifnumEntries < 0

SizeSequence
public SizeSequence(int numEntries, int value) Creates a newSizeSequence
object that contains the specified number of entries, all initialized to have sizevalue
. Parameters:
numEntries
 the number of sizes to trackvalue
 the initial value of each size

SizeSequence
public SizeSequence(int[] sizes) Creates a newSizeSequence
object that contains the specified sizes. Parameters:
sizes
 the array of sizes to be contained in theSizeSequence


Method Details

setSizes
public void setSizes(int[] sizes) Resets thisSizeSequence
object, using the data in thesizes
argument. This method reinitializes this object so that it contains as many entries as thesizes
array. Each entry's size is initialized to the value of the corresponding item insizes
. Parameters:
sizes
 the array of sizes to be contained in thisSizeSequence

getSizes
public int[] getSizes()Returns the size of all entries. Returns:
 a new array containing the sizes in this object

getPosition
public int getPosition(int index) Returns the start position for the specified entry. For example,getPosition(0)
returns 0,getPosition(1)
is equal togetSize(0)
,getPosition(2)
is equal togetSize(0)
+getSize(1)
, and so on.Note that if
index
is greater thanlength
the value returned may be meaningless. Parameters:
index
 the index of the entry whose position is desired Returns:
 the starting position of the specified entry

getIndex
public int getIndex(int position) Returns the index of the entry that corresponds to the specified position. For example,getIndex(0)
is 0, since the first entry always starts at position 0. Parameters:
position
 the position of the entry Returns:
 the index of the entry that occupies the specified position

getSize
public int getSize(int index) Returns the size of the specified entry. Ifindex
is out of the range(0 <= index < getSizes().length)
the behavior is unspecified. Parameters:
index
 the index corresponding to the entry Returns:
 the size of the entry

setSize
public void setSize(int index, int size) Sets the size of the specified entry. Note that if the value ofindex
does not fall in the range:(0 <= index < getSizes().length)
the behavior is unspecified. Parameters:
index
 the index corresponding to the entrysize
 the size of the entry

insertEntries
public void insertEntries(int start, int length, int value) Adds a contiguous group of entries to thisSizeSequence
. Note that the values ofstart
andlength
must satisfy the following conditions:(0 <= start < getSizes().length) AND (length >= 0)
. If these conditions are not met, the behavior is unspecified and an exception may be thrown. Parameters:
start
 the index to be assigned to the first entry in the grouplength
 the number of entries in the groupvalue
 the size to be assigned to each new entry Throws:
ArrayIndexOutOfBoundsException
 if the parameters are outside of the range: (0 <= start < (getSizes().length)) AND (length >= 0)

removeEntries
public void removeEntries(int start, int length) Removes a contiguous group of entries from thisSizeSequence
. Note that the values ofstart
andlength
must satisfy the following conditions:(0 <= start < getSizes().length) AND (length >= 0)
. If these conditions are not met, the behavior is unspecified and an exception may be thrown. Parameters:
start
 the index of the first entry to be removedlength
 the number of entries to be removed
