public class SizeSequence extends Object
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.
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.
Constructor and Description 

SizeSequence()
Creates a new
SizeSequence object
that contains no entries. 
SizeSequence(int numEntries)
Creates a new
SizeSequence object
that contains the specified number of entries,
all initialized to have size 0. 
SizeSequence(int[] sizes)
Creates a new
SizeSequence object
that contains the specified sizes. 
SizeSequence(int numEntries,
int value)
Creates a new
SizeSequence object
that contains the specified number of entries,
all initialized to have size value . 
Modifier and Type  Method and Description 

int 
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 this
SizeSequence . 
void 
removeEntries(int start,
int length)
Removes a contiguous group of entries
from this
SizeSequence . 
void 
setSize(int index,
int size)
Sets the size of the specified entry.

void 
setSizes(int[] sizes)
Resets this
SizeSequence object,
using the data in the sizes argument. 
public SizeSequence()
SizeSequence
object
that contains no entries. To add entries, you
can use insertEntries
or setSizes
.insertEntries(int, int, int)
,
setSizes(int[])
public SizeSequence(int numEntries)
SizeSequence
object
that contains the specified number of entries,
all initialized to have size 0.numEntries
 the number of sizes to trackNegativeArraySizeException
 if
numEntries < 0
public SizeSequence(int numEntries, int value)
SizeSequence
object
that contains the specified number of entries,
all initialized to have size value
.numEntries
 the number of sizes to trackvalue
 the initial value of each sizepublic SizeSequence(int[] sizes)
SizeSequence
object
that contains the specified sizes.sizes
 the array of sizes to be contained in
the SizeSequence
public void setSizes(int[] sizes)
SizeSequence
object,
using the data in the sizes
argument.
This method reinitializes this object so that it
contains as many entries as the sizes
array.
Each entry's size is initialized to the value of the
corresponding item in sizes
.sizes
 the array of sizes to be contained in
this SizeSequence
public int[] getSizes()
public int getPosition(int index)
getPosition(0)
returns 0,
getPosition(1)
is equal to
getSize(0)
,
getPosition(2)
is equal to
getSize(0)
+ getSize(1)
,
and so on.
Note that if index
is greater than
length
the value returned may
be meaningless.
index
 the index of the entry whose position is desiredpublic int getIndex(int position)
getIndex(0)
is 0,
since the first entry always starts at position 0.position
 the position of the entrypublic int getSize(int index)
index
is out of the range
(0 <= index < getSizes().length)
the behavior is unspecified.index
 the index corresponding to the entrypublic void setSize(int index, int size)
index
does not fall in the range:
(0 <= index < getSizes().length)
the behavior is unspecified.index
 the index corresponding to the entrysize
 the size of the entrypublic void insertEntries(int start, int length, int value)
SizeSequence
.
Note that the values of start
and
length
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.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 entryArrayIndexOutOfBoundsException
 if the parameters
are outside of the range:
(0 <= start < (getSizes().length)) AND (length >= 0)
public void removeEntries(int start, int length)
SizeSequence
.
Note that the values of start
and
length
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.start
 the index of the first entry to be removedlength
 the number of entries to be removed