Class Area
- java.lang.Object
-
- java.awt.geom.Area
public class Area extends Object implements Shape, Cloneable
An Area
object stores and manipulates a resolution-independent description of an enclosed area of 2-dimensional space. Area
objects can be transformed and can perform various Constructive Area Geometry (CAG) operations when combined with other Area
objects. The CAG operations include area addition
, subtraction
, intersection
, and exclusive or
. See the linked method documentation for examples of the various operations.
The Area
class implements the Shape
interface and provides full support for all of its hit-testing and path iteration facilities, but an Area
is more specific than a generalized path in a number of ways:
- Only closed paths and sub-paths are stored.
Area
objects constructed from unclosed paths are implicitly closed during construction as if those paths had been filled by theGraphics2D.fill
method. - The interiors of the individual stored sub-paths are all non-empty and non-overlapping. Paths are decomposed during construction into separate component non-overlapping parts, empty pieces of the path are discarded, and then these non-empty and non-overlapping properties are maintained through all subsequent CAG operations. Outlines of different component sub-paths may touch each other, as long as they do not cross so that their enclosed areas overlap.
- The geometry of the path describing the outline of the
Area
resembles the path from which it was constructed only in that it describes the same enclosed 2-dimensional area, but may use entirely different types and ordering of the path segments to do so.
Area
include: - Creating an
Area
from an unclosed (open)Shape
results in a closed outline in theArea
object. - Creating an
Area
from aShape
which encloses no area (even when "closed") produces an emptyArea
. A common example of this issue is that producing anArea
from a line will be empty since the line encloses no area. An emptyArea
will iterate no geometry in itsPathIterator
objects. - A self-intersecting
Shape
may be split into two (or more) sub-paths each enclosing one of the non-intersecting portions of the original path. - An
Area
may take more path segments to describe the same geometry even when the original outline is simple and obvious. The analysis that theArea
class must perform on the path may not reflect the same concepts of "simple and obvious" as a human being perceives.
- Since:
- 1.2
Constructor Summary
Constructor | Description |
---|---|
Area() | Default constructor which creates an empty area. |
Area(Shape s) | The |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
void | add(Area rhs) | Adds the shape of the specified |
Object | clone() | Returns an exact copy of this |
boolean | contains(double x,
double y) | Tests if the specified coordinates are inside the boundary of the |
boolean | contains(double x,
double y,
double w,
double h) | Tests if the interior of the |
boolean | contains(Point2D p) | Tests if a specified |
boolean | contains(Rectangle2D r) | Tests if the interior of the |
Area | createTransformedArea(AffineTransform t) | Creates a new |
boolean | equals(Area other) | Tests whether the geometries of the two |
void | exclusiveOr(Area rhs) | Sets the shape of this |
Rectangle | getBounds() | Returns a bounding |
Rectangle2D | getBounds2D() | Returns a high precision bounding |
PathIterator | getPathIterator(AffineTransform at) | Creates a |
PathIterator | getPathIterator(AffineTransform at,
double flatness) | Creates a |
void | intersect(Area rhs) | Sets the shape of this |
boolean | intersects(double x,
double y,
double w,
double h) | Tests if the interior of the |
boolean | intersects(Rectangle2D r) | Tests if the interior of the |
boolean | isEmpty() | Tests whether this |
boolean | isPolygonal() | Tests whether this |
boolean | isRectangular() | Tests whether this |
boolean | isSingular() | Tests whether this |
void | reset() | Removes all of the geometry from this |
void | subtract(Area rhs) | Subtracts the shape of the specified |
void | transform(AffineTransform t) | Transforms the geometry of this |
Methods declared in class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Constructor Detail
Area
public Area()
Default constructor which creates an empty area.
- Since:
- 1.2
Area
public Area(Shape s)
The Area
class creates an area geometry from the specified Shape
object. The geometry is explicitly closed, if the Shape
is not already closed. The fill rule (even-odd or winding) specified by the geometry of the Shape
is used to determine the resulting enclosed area.
- Parameters:
-
s
- theShape
from which the area is constructed - Throws:
-
NullPointerException
- ifs
is null - Since:
- 1.2
Method Detail
add
public void add(Area rhs)
Adds the shape of the specified Area
to the shape of this Area
. The resulting shape of this Area
will include the union of both shapes, or all areas that were contained in either this or the specified Area
.
// Example: Area a1 = new Area([triangle 0,0 => 8,0 => 0,8]); Area a2 = new Area([triangle 0,0 => 8,0 => 8,8]); a1.add(a2); a1(before) + a2 = a1(after) ################ ################ ################ ############## ############## ################ ############ ############ ################ ########## ########## ################ ######## ######## ################ ###### ###### ###### ###### #### #### #### #### ## ## ## ##
- Parameters:
-
rhs
- theArea
to be added to the current shape - Throws:
-
NullPointerException
- ifrhs
is null - Since:
- 1.2
subtract
public void subtract(Area rhs)
Subtracts the shape of the specified Area
from the shape of this Area
. The resulting shape of this Area
will include areas that were contained only in this Area
and not in the specified Area
.
// Example: Area a1 = new Area([triangle 0,0 => 8,0 => 0,8]); Area a2 = new Area([triangle 0,0 => 8,0 => 8,8]); a1.subtract(a2); a1(before) - a2 = a1(after) ################ ################ ############## ############## ## ############ ############ #### ########## ########## ###### ######## ######## ######## ###### ###### ###### #### #### #### ## ## ##
- Parameters:
-
rhs
- theArea
to be subtracted from the current shape - Throws:
-
NullPointerException
- ifrhs
is null - Since:
- 1.2
intersect
public void intersect(Area rhs)
Sets the shape of this Area
to the intersection of its current shape and the shape of the specified Area
. The resulting shape of this Area
will include only areas that were contained in both this Area
and also in the specified Area
.
// Example: Area a1 = new Area([triangle 0,0 => 8,0 => 0,8]); Area a2 = new Area([triangle 0,0 => 8,0 => 8,8]); a1.intersect(a2); a1(before) intersect a2 = a1(after) ################ ################ ################ ############## ############## ############ ############ ############ ######## ########## ########## #### ######## ######## ###### ###### #### #### ## ##
- Parameters:
-
rhs
- theArea
to be intersected with thisArea
- Throws:
-
NullPointerException
- ifrhs
is null - Since:
- 1.2
exclusiveOr
public void exclusiveOr(Area rhs)
Sets the shape of this Area
to be the combined area of its current shape and the shape of the specified Area
, minus their intersection. The resulting shape of this Area
will include only areas that were contained in either this Area
or in the specified Area
, but not in both.
// Example: Area a1 = new Area([triangle 0,0 => 8,0 => 0,8]); Area a2 = new Area([triangle 0,0 => 8,0 => 8,8]); a1.exclusiveOr(a2); a1(before) xor a2 = a1(after) ################ ################ ############## ############## ## ## ############ ############ #### #### ########## ########## ###### ###### ######## ######## ################ ###### ###### ###### ###### #### #### #### #### ## ## ## ##
- Parameters:
-
rhs
- theArea
to be exclusive ORed with thisArea
. - Throws:
-
NullPointerException
- ifrhs
is null - Since:
- 1.2
reset
public void reset()
Removes all of the geometry from this Area
and restores it to an empty area.
- Since:
- 1.2
isEmpty
public boolean isEmpty()
Tests whether this Area
object encloses any area.
- Returns:
-
true
if thisArea
object represents an empty area;false
otherwise. - Since:
- 1.2
isPolygonal
public boolean isPolygonal()
Tests whether this Area
consists entirely of straight edged polygonal geometry.
- Returns:
-
true
if the geometry of thisArea
consists entirely of line segments;false
otherwise. - Since:
- 1.2
isRectangular
public boolean isRectangular()
Tests whether this Area
is rectangular in shape.
- Returns:
-
true
if the geometry of thisArea
is rectangular in shape;false
otherwise. - Since:
- 1.2
isSingular
public boolean isSingular()
Tests whether this Area
is comprised of a single closed subpath. This method returns true
if the path contains 0 or 1 subpaths, or false
if the path contains more than 1 subpath. The subpaths are counted by the number of SEG_MOVETO
segments that appear in the path.
- Returns:
-
true
if theArea
is comprised of a single basic geometry;false
otherwise. - Since:
- 1.2
getBounds2D
public Rectangle2D getBounds2D()
Returns a high precision bounding Rectangle2D
that completely encloses this Area
.
The Area class will attempt to return the tightest bounding box possible for the Shape. The bounding box will not be padded to include the control points of curves in the outline of the Shape, but should tightly fit the actual geometry of the outline itself.
- Specified by:
-
getBounds2D
in interfaceShape
- Returns:
- the bounding
Rectangle2D
for theArea
. - Since:
- 1.2
- See Also:
Shape.getBounds()
getBounds
public Rectangle getBounds()
Returns a bounding Rectangle
that completely encloses this Area
.
The Area class will attempt to return the tightest bounding box possible for the Shape. The bounding box will not be padded to include the control points of curves in the outline of the Shape, but should tightly fit the actual geometry of the outline itself. Since the returned object represents the bounding box with integers, the bounding box can only be as tight as the nearest integer coordinates that encompass the geometry of the Shape.
- Specified by:
-
getBounds
in interfaceShape
- Returns:
- the bounding
Rectangle
for theArea
. - Since:
- 1.2
- See Also:
Shape.getBounds2D()
clone
public Object clone()
Returns an exact copy of this Area
object.
equals
public boolean equals(Area other)
Tests whether the geometries of the two Area
objects are equal. This method will return false if the argument is null.
- Parameters:
-
other
- theArea
to be compared to thisArea
- Returns:
-
true
if the two geometries are equal;false
otherwise. - Since:
- 1.2
transform
public void transform(AffineTransform t)
Transforms the geometry of this Area
using the specified AffineTransform
. The geometry is transformed in place, which permanently changes the enclosed area defined by this object.
- Parameters:
-
t
- the transformation used to transform the area - Throws:
-
NullPointerException
- ift
is null - Since:
- 1.2
createTransformedArea
public Area createTransformedArea(AffineTransform t)
Creates a new Area
object that contains the same geometry as this Area
transformed by the specified AffineTransform
. This Area
object is unchanged.
- Parameters:
-
t
- the specifiedAffineTransform
used to transform the newArea
- Returns:
- a new
Area
object representing the transformed geometry. - Throws:
-
NullPointerException
- ift
is null - Since:
- 1.2
contains
public boolean contains(double x, double y)
Tests if the specified coordinates are inside the boundary of the Shape
, as described by the definition of insideness.
- Specified by:
-
contains
in interfaceShape
- Parameters:
-
x
- the specified X coordinate to be tested -
y
- the specified Y coordinate to be tested - Returns:
-
true
if the specified coordinates are inside theShape
boundary;false
otherwise. - Since:
- 1.2
contains
public boolean contains(Point2D p)
Tests if a specified Point2D
is inside the boundary of the Shape
, as described by the definition of insideness.
- Specified by:
-
contains
in interfaceShape
- Parameters:
-
p
- the specifiedPoint2D
to be tested - Returns:
-
true
if the specifiedPoint2D
is inside the boundary of theShape
;false
otherwise. - Since:
- 1.2
contains
public boolean contains(double x, double y, double w, double h)
Tests if the interior of the Shape
entirely contains the specified rectangular area. All coordinates that lie inside the rectangular area must lie within the Shape
for the entire rectangular area to be considered contained within the Shape
.
The Shape.contains()
method allows a Shape
implementation to conservatively return false
when:
- the
intersect
method returnstrue
and - the calculations to determine whether or not the
Shape
entirely contains the rectangular area are prohibitively expensive.
Shapes
this method might return false
even though the Shape
contains the rectangular area. The Area
class performs more accurate geometric computations than most Shape
objects and therefore can be used if a more precise answer is required.- Specified by:
-
contains
in interfaceShape
- Parameters:
-
x
- the X coordinate of the upper-left corner of the specified rectangular area -
y
- the Y coordinate of the upper-left corner of the specified rectangular area -
w
- the width of the specified rectangular area -
h
- the height of the specified rectangular area - Returns:
-
true
if the interior of theShape
entirely contains the specified rectangular area;false
otherwise or, if theShape
contains the rectangular area and theintersects
method returnstrue
and the containment calculations would be too expensive to perform. - Since:
- 1.2
- See Also:
-
Area
,Shape.intersects(double, double, double, double)
contains
public boolean contains(Rectangle2D r)
Tests if the interior of the Shape
entirely contains the specified Rectangle2D
. The Shape.contains()
method allows a Shape
implementation to conservatively return false
when:
- the
intersect
method returnstrue
and - the calculations to determine whether or not the
Shape
entirely contains theRectangle2D
are prohibitively expensive.
Shapes
this method might return false
even though the Shape
contains the Rectangle2D
. The Area
class performs more accurate geometric computations than most Shape
objects and therefore can be used if a more precise answer is required. - Specified by:
-
contains
in interfaceShape
- Parameters:
-
r
- The specifiedRectangle2D
- Returns:
-
true
if the interior of theShape
entirely contains theRectangle2D
;false
otherwise or, if theShape
contains theRectangle2D
and theintersects
method returnstrue
and the containment calculations would be too expensive to perform. - Since:
- 1.2
- See Also:
Shape.contains(double, double, double, double)
intersects
public boolean intersects(double x, double y, double w, double h)
Tests if the interior of the Shape
intersects the interior of a specified rectangular area. The rectangular area is considered to intersect the Shape
if any point is contained in both the interior of the Shape
and the specified rectangular area.
The Shape.intersects()
method allows a Shape
implementation to conservatively return true
when:
- there is a high probability that the rectangular area and the
Shape
intersect, but - the calculations to accurately determine this intersection are prohibitively expensive.
Shapes
this method might return true
even though the rectangular area does not intersect the Shape
. The Area
class performs more accurate computations of geometric intersection than most Shape
objects and therefore can be used if a more precise answer is required.- Specified by:
-
intersects
in interfaceShape
- Parameters:
-
x
- the X coordinate of the upper-left corner of the specified rectangular area -
y
- the Y coordinate of the upper-left corner of the specified rectangular area -
w
- the width of the specified rectangular area -
h
- the height of the specified rectangular area - Returns:
-
true
if the interior of theShape
and the interior of the rectangular area intersect, or are both highly likely to intersect and intersection calculations would be too expensive to perform;false
otherwise. - Since:
- 1.2
- See Also:
Area
intersects
public boolean intersects(Rectangle2D r)
Tests if the interior of the Shape
intersects the interior of a specified Rectangle2D
. The Shape.intersects()
method allows a Shape
implementation to conservatively return true
when:
- there is a high probability that the
Rectangle2D
and theShape
intersect, but - the calculations to accurately determine this intersection are prohibitively expensive.
Shapes
this method might return true
even though the Rectangle2D
does not intersect the Shape
. The Area
class performs more accurate computations of geometric intersection than most Shape
objects and therefore can be used if a more precise answer is required. - Specified by:
-
intersects
in interfaceShape
- Parameters:
-
r
- the specifiedRectangle2D
- Returns:
-
true
if the interior of theShape
and the interior of the specifiedRectangle2D
intersect, or are both highly likely to intersect and intersection calculations would be too expensive to perform;false
otherwise. - Since:
- 1.2
- See Also:
Shape.intersects(double, double, double, double)
getPathIterator
public PathIterator getPathIterator(AffineTransform at)
Creates a PathIterator
for the outline of this Area
object. This Area
object is unchanged.
- Specified by:
-
getPathIterator
in interfaceShape
- Parameters:
-
at
- an optionalAffineTransform
to be applied to the coordinates as they are returned in the iteration, ornull
if untransformed coordinates are desired - Returns:
- the
PathIterator
object that returns the geometry of the outline of thisArea
, one segment at a time. - Since:
- 1.2
getPathIterator
public PathIterator getPathIterator(AffineTransform at, double flatness)
Creates a PathIterator
for the flattened outline of this Area
object. Only uncurved path segments represented by the SEG_MOVETO, SEG_LINETO, and SEG_CLOSE point types are returned by the iterator. This Area
object is unchanged.
- Specified by:
-
getPathIterator
in interfaceShape
- Parameters:
-
at
- an optionalAffineTransform
to be applied to the coordinates as they are returned in the iteration, ornull
if untransformed coordinates are desired -
flatness
- the maximum amount that the control points for a given curve can vary from colinear before a subdivided curve is replaced by a straight line connecting the end points - Returns:
- the
PathIterator
object that returns the geometry of the outline of thisArea
, one segment at a time. - Since:
- 1.2