Module java.desktop
Package javax.swing

# Class SizeSequence

java.lang.Object
javax.swing.SizeSequence

public class SizeSequence extends Object
A `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 multi-column 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 multi-column 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 size0 pixels, where size0 is the value returned by `getSize(0)`. Thus, the first column ends at size0 - 1. The second column then begins at the position size0 and occupies size1 (`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 size-based and positional-based 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

Constructors
Constructor
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`.

## Method Summary

Modifier and Type
Method
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.

### Methods declared in class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Constructor Details

### SizeSequence

public SizeSequence()
Creates a new `SizeSequence` object that contains no entries. To add entries, you can use `insertEntries` or `setSizes`.

See Also:
  - `insertEntries(int, int, int)`
  - `setSizes(int[])`

### SizeSequence

public SizeSequence(int numEntries)
Creates a new `SizeSequence` object that contains the specified number of entries, all initialized to have size 0.

Parameters:
  `numEntries` - the number of sizes to track
Throws:
  `NegativeArraySizeException` - if `numEntries < 0`

### SizeSequence

public SizeSequence(int numEntries, int value)
Creates a new `SizeSequence` object that contains the specified number of entries, all initialized to have size `value`.

Parameters:
  `numEntries` - the number of sizes to track
  `value` - the initial value of each size

### SizeSequence

public SizeSequence(int[] sizes)
Creates a new `SizeSequence` object that contains the specified sizes.

Parameters:
  `sizes` - the array of sizes to be contained in the `SizeSequence`

## Method Details

### setSizes

public void setSizes(int[] sizes)
Resets this `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`.

Parameters:
  `sizes` - the array of sizes to be contained in this `SizeSequence`

### 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 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.

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. If `index` 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 of `index` does not fall in the range: `(0 <= index < getSizes().length)` the behavior is unspecified.

Parameters:
  `index` - the index corresponding to the entry
  `size` - the size of the entry

### insertEntries

public void insertEntries(int start, int length, int value)
Adds a contiguous group of entries to this `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.

Parameters:
  `start` - the index to be assigned to the first entry in the group
  `length` - the number of entries in the group
  `value` - 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 this `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.

Parameters:
  `start` - the index of the first entry to be removed
  `length` - the number of entries to be removed