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java.lang.Object java.awt.Polygon
The Polygon
class encapsulates a description of a
closed, two-dimensional region within a coordinate space. This
region is bounded by an arbitrary number of line segments, each of
which is one side of the polygon. Internally, a polygon
comprises of a list of (x, y)
coordinate pairs, where each pair defines a vertex of the
polygon, and two successive pairs are the endpoints of a
line that is a side of the polygon. The first and final
pairs of (x, y) points are joined by a line segment
that closes the polygon. This Polygon
is defined with
an even-odd winding rule.
(The even-odd rule specifies that a point lies inside the path if a ray drawn in any direction from that point to infinity is crossed by path segments an odd number of times.)
This class's hit-testing methods, which include the
contains
, intersects
and inside
methods, use the insideness definition described in the
Shape
class comments.
Shape
,
Serialized FormField Summary | |
protected Rectangle |
bounds
Bounds of the polygon. |
int |
npoints
The total number of points. |
int[] |
xpoints
The array of x coordinates. |
int[] |
ypoints
The array of y coordinates. |
Constructor Summary | |
Polygon()
Creates an empty polygon. |
|
Polygon(int[] xpoints,
int[] ypoints,
int npoints)
Constructs and initializes a Polygon from the specified
parameters. |
Method Summary | |
void |
addPoint(int x,
int y)
Appends the specified coordinates to this Polygon . |
boolean |
contains(int x,
int y)
Determines whether the specified coordinates are inside this Polygon . |
boolean |
contains(Point p)
Determines whether the specified Point is inside this
Polygon . |
Rectangle |
getBounds()
Gets the bounding box of this Polygon . |
void |
invalidate()
Invalidates or flushes any internally-cached data that depends on the vertex coordinates of this Polygon . |
void |
reset()
Resets this Polygon object to an empty polygon. |
void |
translate(int deltaX,
int deltaY)
Translates the vertices of the Polygon by
deltaX along the x axis and by
deltaY along the y axis. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public int npoints
npoints
represents the number of valid points in this Polygon
and might be less than the number of elements in
xpoints
or ypoints
.
This value can be NULL.
addPoint(int, int)
public int[] xpoints
Polygon
. The extra elements allow new points
to be added to this Polygon
without re-creating this
array. The value of npoints
is equal to the
number of valid points in this Polygon
.
addPoint(int, int)
public int[] ypoints
Polygon
. The extra elements allow new points
to be added to this Polygon
without re-creating this
array. The value of npoints
is equal to the
number of valid points in this Polygon
.
addPoint(int, int)
protected Rectangle bounds
getBounds()
Constructor Detail |
public Polygon()
public Polygon(int[] xpoints, int[] ypoints, int npoints)
Polygon
from the specified
parameters.
xpoints
- an array of x coordinatesypoints
- an array of y coordinatesnpoints
- the total number of points in the
Polygon
NegativeArraySizeException
- if the value of
npoints
is negative.
IndexOutOfBoundsException
- if npoints
is
greater than the length of xpoints
or the length of ypoints
.
NullPointerException
- if xpoints
or
ypoints
is null
.Method Detail |
public void reset()
Polygon
object to an empty polygon.
The coordinate arrays and the data in them are left untouched
but the number of points is reset to zero to mark the old
vertex data as invalid and to start accumulating new vertex
data at the beginning.
All internally-cached data relating to the old vertices
are discarded.
Note that since the coordinate arrays from before the reset
are reused, creating a new empty Polygon
might
be more memory efficient than resetting the current one if
the number of vertices in the new polygon data is significantly
smaller than the number of vertices in the data from before the
reset.
invalidate()
public void invalidate()
Polygon
.
This method should be called after any direct manipulation
of the coordinates in the xpoints
or
ypoints
arrays to avoid inconsistent results
from methods such as getBounds
or contains
that might cache data from earlier computations relating to
the vertex coordinates.
getBounds()
public void translate(int deltaX, int deltaY)
Polygon
by
deltaX
along the x axis and by
deltaY
along the y axis.
deltaX
- the amount to translate along the x axisdeltaY
- the amount to translate along the y axispublic void addPoint(int x, int y)
Polygon
.
If an operation that calculates the bounding box of this
Polygon
has already been performed, such as
getBounds
or contains
, then this
method updates the bounding box.
x
- the specified x coordinatey
- the specified y coordinategetBounds()
,
contains(java.awt.Point)
public Rectangle getBounds()
Polygon
.
The bounding box is the smallest Rectangle
whose
sides are parallel to the x and y axes of the
coordinate space, and can completely contain the Polygon
.
getBounds
in interface Shape
Rectangle
that defines the bounds of this
Polygon
.public boolean contains(Point p)
Point
is inside this
Polygon
.
p
- the specified Point
to be tested
true
if the Polygon
contains the
Point
; false
otherwise.public boolean contains(int x, int y)
Polygon
.
x
- the specified x coordinate to be testedy
- the specified y coordinate to be tested
true
if this Polygon
contains
the specified coordinates, (x, y);
false
otherwise.
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