Class: java.awt.geom.Area

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 the Graphics2D.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.
Interesting issues which are not always obvious when using the Area include:
  • Creating an Area from an unclosed (open) Shape results in a closed outline in the Area object.
  • Creating an Area from a Shape which encloses no area (even when "closed") produces an empty Area. A common example of this issue is that producing an Area from a line will be empty since the line encloses no area. An empty Area will iterate no geometry in its PathIterator 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 the Area class must perform on the path may not reflect the same concepts of "simple and obvious" as a human being perceives.
Since:
@since 1.2

Inheritance

Superclass tree: Implements:

Methods

  • Areatop

    public Area()
    Default constructor which creates an empty area.
    Since:
    @since 1.2
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  • Areatop

    public Area(Shape s)
    The Area class creates an area geometry from the specified java.awt.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:
    @param s the Shape from which the area is constructed
    Exceptions:
    @throws NullPointerException if s is null
    Since:
    @since 1.2
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  • addtop

    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)

     ################     ################     ################
     ##############         ##############     ################
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     ########                     ########     ################
     ######                         ######     ######    ######
     ####                             ####     ####        ####
     ##                                 ##     ##            ##
    Parameters:
    @param rhs the Area to be added to the current shape
    Exceptions:
    @throws NullPointerException if rhs is null
    Since:
    @since 1.2
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  • clonetop

    public Object clone()
    Returns an exact copy of this Area object.
    Return:
    @return Created clone object
    Since:
    @since 1.2
    Override hierarchy:
    clone from Object
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  • containstop

    public boolean contains(double x, double y)
    Tests if the specified coordinates are inside the boundary of the Shape.
    Parameters:
    @param x the specified X coordinate to be tested
    @param y the specified Y coordinate to be tested
    Return:
    @return true if the specified coordinates are inside the Shape boundary; false otherwise.
    Since:
    @since 1.2
    Specified by:
    contains from Shape
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  • containstop

    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 rectanglar 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.
    Parameters:
    @param x the X coordinate of the upper-left corner of the specified rectangular area
    @param y the Y coordinate of the upper-left corner of the specified rectangular area
    @param w the width of the specified rectangular area
    @param h the height of the specified rectangular area
    Return:
    @return 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:
    @since 1.2
    Specified by:
    contains from Shape
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  • containstop

    public boolean contains(Point2D p)
    Tests if a specified java.awt.geom.Point2D is inside the boundary of the Shape.
    Parameters:
    @param p the specified Point2D to be tested
    Return:
    @return true if the specified Point2D is inside the boundary of the Shape; false otherwise.
    Since:
    @since 1.2
    Specified by:
    contains from Shape
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  • containstop

    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.
    Parameters:
    @param r The specified Rectangle2D
    Return:
    @return 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:
    @since 1.2
    Specified by:
    contains from Shape
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  • createTransformedAreatop

    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:
    @param t the specified AffineTransform used to transform the new Area
    Return:
    @return a new Area object representing the transformed geometry.
    Exceptions:
    @throws NullPointerException if t is null
    Since:
    @since 1.2
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  • equalstop

    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:
    @param other the Area to be compared to this Area
    Return:
    @return true if the two geometries are equal; false otherwise.
    Since:
    @since 1.2
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  • exclusiveOrtop

    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)

     ################     ################
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     ############             ############     ####        ####
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     ########                     ########     ################
     ######                         ######     ######    ######
     ####                             ####     ####        ####
     ##                                 ##     ##            ##
    Parameters:
    @param rhs the Area to be exclusive ORed with this Area.
    Exceptions:
    @throws NullPointerException if rhs is null
    Since:
    @since 1.2
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  • getBoundstop

    public Rectangle getBounds()
    Returns a bounding java.awt.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.

    Return:
    @return the bounding Rectangle for the Area.
    Since:
    @since 1.2
    Specified by:
    getBounds from Shape
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  • getBounds2Dtop

    public Rectangle2D getBounds2D()
    Returns a high precision bounding java.awt.geom.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.

    Return:
    @return the bounding Rectangle2D for the Area.
    Since:
    @since 1.2
    Specified by:
    getBounds2D from Shape
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  • getCachedBoundstop

    private Rectangle2D getCachedBounds()
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  • getPathIteratortop

    public PathIterator getPathIterator(AffineTransform at)
    Creates a java.awt.geom.PathIterator for the outline of this Area object. This Area object is unchanged.
    Parameters:
    @param at an optional AffineTransform to be applied to the coordinates as they are returned in the iteration, or null if untransformed coordinates are desired
    Return:
    @return the PathIterator object that returns the geometry of the outline of this Area, one segment at a time.
    Since:
    @since 1.2
    Specified by:
    getPathIterator from Shape
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  • getPathIteratortop

    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.
    Parameters:
    @param at an optional AffineTransform to be applied to the coordinates as they are returned in the iteration, or null if untransformed coordinates are desired
    @param 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
    Return:
    @return the PathIterator object that returns the geometry of the outline of this Area, one segment at a time.
    Since:
    @since 1.2
    Specified by:
    getPathIterator from Shape
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  • intersecttop

    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:
    @param rhs the Area to be intersected with this Area
    Exceptions:
    @throws NullPointerException if rhs is null
    Since:
    @since 1.2
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  • intersectstop

    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.
    Parameters:
    @param x the X coordinate of the upper-left corner of the specified rectangular area
    @param y the Y coordinate of the upper-left corner of the specified rectangular area
    @param w the width of the specified rectangular area
    @param h the height of the specified rectangular area
    Return:
    @return 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:
    @since 1.2
    Specified by:
    intersects from Shape
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  • intersectstop

    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.
    Parameters:
    @param r the specified Rectangle2D
    Return:
    @return 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:
    @since 1.2
    Specified by:
    intersects from Shape
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  • invalidateBoundstop

    private void invalidateBounds()
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  • isEmptytop

    public boolean isEmpty()
    Tests whether this Area object encloses any area.
    Return:
    @return true if this Area object represents an empty area; false otherwise.
    Since:
    @since 1.2
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  • isPolygonaltop

    public boolean isPolygonal()
    Tests whether this Area consists entirely of straight edged polygonal geometry.
    Return:
    @return true if the geometry of this Area consists entirely of line segments; false otherwise.
    Since:
    @since 1.2
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  • isRectangulartop

    public boolean isRectangular()
    Tests whether this Area is rectangular in shape.
    Return:
    @return true if the geometry of this Area is rectangular in shape; false otherwise.
    Since:
    @since 1.2
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  • isSingulartop

    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.
    Return:
    @return true if the Area is comprised of a single basic geometry; false otherwise.
    Since:
    @since 1.2
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  • pathToCurvestop

    static private Vector pathToCurves(PathIterator pi)
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  • resettop

    public void reset()
    Removes all of the geometry from this Area and restores it to an empty area.
    Since:
    @since 1.2
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  • subtracttop

    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:
    @param rhs the Area to be subtracted from the current shape
    Exceptions:
    @throws NullPointerException if rhs is null
    Since:
    @since 1.2
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  • transformtop

    public void transform(AffineTransform t)
    Transforms the geometry of this Area using the specified java.awt.geom.AffineTransform. The geometry is transformed in place, which permanently changes the enclosed area defined by this object.
    Parameters:
    @param t the transformation used to transform the area
    Exceptions:
    @throws NullPointerException if t is null
    Since:
    @since 1.2
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Fields

  • EmptyCurves

    static private Vector EmptyCurves

  • cachedBounds

    private Rectangle2D cachedBounds

  • curves

    private Vector curves