java.awt
Class Polygon

java.lang.Object
  |
  +--java.awt.Polygon

All Implemented Interfaces:

Serializable, Shape

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:

JDK1.0

See Also:

Shape, Serialized Form

Field 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(double x, double y) Determines if the specified coordinates are inside this Polygon.
boolean	contains(double x, double y, double w, double h) Tests if the interior of this Polygon entirely contains the specified set of rectangular coordinates.
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.
boolean	contains(Point2D p) Tests if a specified Point2D is inside the boundary of this Polygon.
boolean	contains(Rectangle2D r) Tests if the interior of this Polygon entirely contains the specified Rectangle2D.
Rectangle	getBoundingBox() Deprecated. As of JDK version 1.1, replaced by getBounds().
Rectangle	getBounds() Gets the bounding box of this Polygon.
Rectangle2D	getBounds2D() Returns the high precision bounding box of the Shape.
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 this Polygon intersects the interior of a specified set of rectangular coordinates.
boolean	intersects(Rectangle2D r) Tests if the interior of this Polygon 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 inherited from class java.lang.Object

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

Field Detail

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 NULL.

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.

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.

See Also:

addPoint(int, int)

bounds

protected Rectangle bounds

Bounds of the polygon. This value can be NULL. Please see the javadoc comments getBounds().

See Also:

getBoundingBox(), getBounds()

Constructor Detail

Polygon

public Polygon()

Creates an empty polygon.

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.

Method Detail

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:

JDK1.1

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.

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:

JDK1.1

See Also:

Shape.getBounds2D()

getBoundingBox

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.

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.

See Also:

contains(double, double)

contains

public boolean contains(int x,
                        int y)

Determines whether the specified coordinates are inside this Polygon.

Returns:

true if this Polygon contains the specified coordinates, (x, y); false otherwise.

Since:

JDK1.1

See Also:

contains(double, double)

inside

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.

Returns:

true if this Polygon contains the specified coordinates, (x, y); false otherwise.

See Also:

contains(double, double)

getBounds2D

public Rectangle2D getBounds2D()

Returns the high precision bounding box of the Shape.

Specified by:

getBounds2D in interface Shape

Returns:

a Rectangle2D that precisely bounds the Shape.

See Also:

Shape.getBounds()

contains

public boolean contains(double x,
                        double y)

Determines if the specified coordinates are inside this Polygon. For the definition of insideness, see the class comments of Shape.

Specified by:

contains in interface Shape

Returns:

true if the Polygon contains the specified coordinates; false otherwise.

contains

public boolean contains(Point2D p)

Tests if a specified Point2D is inside the boundary of this Polygon.

Specified by:

contains in interface Shape

Parameters:

p - a specified Point2D

Returns:

true if this Polygon contains the specified Point2D; false otherwise.

See Also:

contains(double, double)

intersects

public boolean intersects(double x,
                          double y,
                          double w,
                          double h)

Tests if the interior of this Polygon intersects the interior of a specified set of rectangular coordinates.

Specified by:

intersects in interface Shape

Parameters:

w - the width of the specified rectangular shape

h - the height of the specified rectangular shape

Returns:

true if the interior of this Polygon and the interior of the specified set of rectangular coordinates intersect each other; false otherwise.

See Also:

Area

intersects

public boolean intersects(Rectangle2D r)

Tests if the interior of this Polygon intersects the interior of a specified Rectangle2D.

Specified by:

intersects in interface Shape

Parameters:

r - a specified Rectangle2D

Returns:

true if this Polygon and the interior of the specified Rectangle2D intersect each other; false otherwise.

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 this Polygon entirely contains the specified set of rectangular coordinates.

Specified by:

contains in interface Shape

Parameters:

w - the width of the set of rectangular coordinates

h - the height of the set of rectangular coordinates

Returns:

true if this Polygon entirely contains the specified set of rectangular coordinates; false otherwise.

See Also:

Area, Shape.intersects(double, double, double, double)

contains

public boolean contains(Rectangle2D r)

Tests if the interior of this Polygon entirely contains the specified Rectangle2D.

Specified by:

contains in interface Shape

Parameters:

r - the specified Rectangle2D

Returns:

true if this Polygon entirely contains the specified Rectangle2D; false otherwise.

See Also:

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.

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 colinear 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.