Class Polygon

All Implemented Interfaces:
Shape, Serializable 
public class Polygon
extends Object
implements Shape, Serializable

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. See WIND_EVEN_ODD for a definition of the even-odd winding rule. This class's hit-testing methods, which include the contains, intersects and inside methods, use the insideness definition described in the Shape class comments.

Since:
1.0
See Also:
Shape, Serialized Form

Fields

Modifier and Type Field Description
protected Rectangle bounds

The bounds of this Polygon.
int npoints

The total number of points.
int[] xpoints

The array of X coordinates.
int[] ypoints

The array of Y coordinates.

Constructors

Constructor Description
Polygon()

Creates an empty polygon.
Polygon​(int[] xpoints, int[] ypoints, int npoints)

Constructs and initializes a Polygon from the specified parameters.

Methods

Modifier and Type Method Description
void addPoint​(int x, int y)

Appends the specified coordinates to this Polygon.
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.
boolean contains​(double x, double y, double w, double h)

Tests if the interior of the Shape entirely contains the specified rectangular area.
boolean contains​(int x, int y)

Determines whether the specified coordinates are inside this Polygon.
boolean contains​(Point2D p)

Tests if a specified Point2D is inside the boundary of the Shape, as described by the definition of insideness.
boolean contains​(Rectangle2D r)

Tests if the interior of the Shape entirely contains the specified Rectangle2D.
boolean contains​(Point p)

Determines whether the specified Point is inside this Polygon.
Rectangle getBoundingBox()

Deprecated.

As of JDK version 1.1, replaced by getBounds().
Rectangle getBounds()

Gets the bounding box of this Polygon.
Rectangle2D getBounds2D()

Returns a high precision and more accurate bounding box of the Shape than the getBounds method.
PathIterator getPathIterator​(AffineTransform at)

Returns an iterator object that iterates along the boundary of this Polygon and provides access to the geometry of the outline of this Polygon.
PathIterator getPathIterator​(AffineTransform at, double flatness)

Returns an iterator object that iterates along the boundary of the Shape and provides access to the geometry of the outline of the Shape.
boolean inside​(int x, int y)

Deprecated.

As of JDK version 1.1, replaced by contains(int, int).
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.
boolean intersects​(Rectangle2D r)

Tests if the interior of the Shape intersects the interior of a specified Rectangle2D.
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 declared in class java.lang.Object

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

Fields

npoints

public int npoints

The total number of points. The value of 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 0.

Since:
1.0
See Also:
addPoint(int, int)

xpoints

public int[] xpoints

The array of X coordinates. The number of elements in this array might be more than the number of X coordinates in this 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.

Since:
1.0
See Also:
addPoint(int, int)

ypoints

public int[] ypoints

The array of Y coordinates. The number of elements in this array might be more than the number of Y coordinates in this 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.

Since:
1.0
See Also:
addPoint(int, int)

bounds

protected Rectangle bounds

The bounds of this Polygon. This value can be null.

Since:
1.0
See Also:
getBoundingBox(), getBounds()

Constructors

Polygon

public Polygon()

Creates an empty polygon.

Since:
1.0

Polygon

public Polygon(int[] xpoints,
               int[] ypoints,
               int npoints)

Constructs and initializes a Polygon from the specified parameters.

Parameters:
xpoints - an array of X coordinates
ypoints - an array of Y coordinates
npoints - the total number of points in the Polygon
Throws:
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.
Since:
1.0

Methods

reset

public void reset()

Resets this 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.

Since:
1.4
See Also:
invalidate()

invalidate

public void invalidate()

Invalidates or flushes any internally-cached data that depends on the vertex coordinates of this 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.

Since:
1.4
See Also:
getBounds()

translate

public 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.

Parameters:
deltaX - the amount to translate along the X axis
deltaY - the amount to translate along the Y axis
Since:
1.1

addPoint

public void addPoint(int x,
                     int y)

Appends the specified coordinates to this 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.

Parameters:
x - the specified X coordinate
y - the specified Y coordinate
Since:
1.0
See Also:
getBounds(), contains(java.awt.Point)

getBounds

public Rectangle getBounds()

Gets the bounding box of this 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.

Specified by:
getBounds in interface Shape
Returns:
a Rectangle that defines the bounds of this Polygon.
Since:
1.1
See Also:
Shape.getBounds2D()

getBoundingBox

@Deprecated
public Rectangle getBoundingBox()
Deprecated.
As of JDK version 1.1, replaced by getBounds().

Returns the bounds of this Polygon.

Returns:
the bounds of this Polygon.
Since:
1.0

contains

public boolean contains(Point p)

Determines whether the specified Point is inside this Polygon.

Parameters:
p - the specified Point to be tested
Returns:
true if the Polygon contains the Point; false otherwise.
Since:
1.0
See Also:
contains(double, double)

contains

public boolean contains(int x,
                        int y)

Determines whether the specified coordinates are inside this Polygon.

Parameters:
x - the specified X coordinate to be tested
y - the specified Y coordinate to be tested
Returns:
true if this Polygon contains the specified coordinates (x,y); false otherwise.
Since:
1.1
See Also:
contains(double, double)

inside

@Deprecated
public boolean inside(int x,
                      int y)
Deprecated.
As of JDK version 1.1, replaced by contains(int, int).

Determines whether the specified coordinates are contained in this Polygon.

Parameters:
x - the specified X coordinate to be tested
y - the specified Y coordinate to be tested
Returns:
true if this Polygon contains the specified coordinates (x,y); false otherwise.
Since:
1.0
See Also:
contains(double, double)

getBounds2D

public Rectangle2D getBounds2D()

Returns a high precision and more accurate bounding box of the Shape than the getBounds method. Note that there is no guarantee that the returned Rectangle2D is the smallest bounding box that encloses the Shape, only that the Shape lies entirely within the indicated Rectangle2D. The bounding box returned by this method is usually tighter than that returned by the getBounds method and never fails due to overflow problems since the return value can be an instance of the Rectangle2D that uses double precision values to store the dimensions.

Note that the definition of insideness can lead to situations where points on the defining outline of the shape may not be considered contained in the returned bounds object, but only in cases where those points are also not considered contained in the original shape.

If a point is inside the shape according to the contains(point) method, then it must be inside the returned Rectangle2D bounds object according to the contains(point) method of the bounds. Specifically:

shape.contains(p) requires bounds.contains(p)

If a point is not inside the shape, then it might still be contained in the bounds object:

bounds.contains(p) does not imply shape.contains(p)

Specified by:
getBounds2D in interface Shape
Returns:
an instance of Rectangle2D that is a high-precision bounding box of the Shape.
Since:
1.2
See Also:
Shape.getBounds()

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 interface Shape
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 the Shape 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 interface Shape
Parameters:
p - the specified Point2D to be tested
Returns:
true if the specified Point2D is inside the boundary of the Shape; false otherwise.
Since:
1.2

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.
This means that for some 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 interface Shape
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 the Shape 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 the Shape intersect, but
  • the calculations to accurately determine this intersection are prohibitively expensive.
This means that for some 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 interface Shape
Parameters:
r - the specified Rectangle2D
Returns:
true if the interior of the Shape and the interior of the specified Rectangle2D 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)

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 returns true and
  • the calculations to determine whether or not the Shape entirely contains the rectangular area are prohibitively expensive.
This means that for some 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 interface Shape
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 the Shape entirely contains the specified rectangular area; false otherwise or, if the Shape contains the rectangular area and the intersects method returns true 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 returns true and
  • the calculations to determine whether or not the Shape entirely contains the Rectangle2D are prohibitively expensive.
This means that for some 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 interface Shape
Parameters:
r - The specified Rectangle2D
Returns:
true if the interior of the Shape entirely contains the Rectangle2D; false otherwise or, if the Shape contains the Rectangle2D and the intersects method returns true and the containment calculations would be too expensive to perform.
Since:
1.2
See Also:
Shape.contains(double, double, double, double)

getPathIterator

public PathIterator getPathIterator(AffineTransform at)

Returns an iterator object that iterates along the boundary of this Polygon and provides access to the geometry of the outline of this Polygon. An optional AffineTransform can be specified so that the coordinates returned in the iteration are transformed accordingly.

Specified by:
getPathIterator in interface Shape
Parameters:
at - an optional AffineTransform to be applied to the coordinates as they are returned in the iteration, or null if untransformed coordinates are desired
Returns:
a PathIterator object that provides access to the geometry of this Polygon.
Since:
1.2

getPathIterator

public PathIterator getPathIterator(AffineTransform at,
                                    double flatness)

Returns an iterator object that iterates along the boundary of the Shape and provides access to the geometry of the outline of the Shape. Only SEG_MOVETO, SEG_LINETO, and SEG_CLOSE point types are returned by the iterator. Since polygons are already flat, the flatness parameter is ignored. An optional AffineTransform can be specified in which case the coordinates returned in the iteration are transformed accordingly.

Specified by:
getPathIterator in interface Shape
Parameters:
at - an optional AffineTransform to be applied to the coordinates as they are returned in the iteration, or null if untransformed coordinates are desired
flatness - the maximum amount that the control points for a given curve can vary from collinear before a subdivided curve is replaced by a straight line connecting the endpoints. Since polygons are already flat the flatness parameter is ignored.
Returns:
a PathIterator object that provides access to the Shape object's geometry.
Since:
1.2

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