Class Polygon

• java.lang.Object
• • java.awt.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

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.

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)

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)

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()

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)

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)

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 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.

Since:

1.2