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Line2D.javaAPI DocJava SE 5 API35841Fri Aug 26 14:56:52 BST 2005java.awt.geom

Line2D

public abstract class Line2D extends Object implements Shape, Cloneable
This Line2D represents a line segment in (x, y) coordinate space. This class, like all of the Java 2D API, uses a default coordinate system called user space in which the y-axis values increase downward and x-axis values increase to the right. For more information on the user space coordinate system, see the Coordinate Systems section of the Java 2D Programmer's Guide.

This class is only the abstract superclass for all objects that store a 2D line segment. The actual storage representation of the coordinates is left to the subclass.

version
1.28, 12/19/03
author
Jim Graham

Fields Summary
Constructors Summary
protected Line2D()
This is an abstract class that cannot be instantiated directly. Type-specific implementation subclasses are available for instantiation and provide a number of formats for storing the information necessary to satisfy the various accessory methods below.

see
java.awt.geom.Line2D.Float
see
java.awt.geom.Line2D.Double

    
Methods Summary
public java.lang.Objectclone()
Creates a new object of the same class as this object.

return
a clone of this instance.
exception
OutOfMemoryError if there is not enough memory.
see
java.lang.Cloneable
since
1.2

	try {
	    return super.clone();
	} catch (CloneNotSupportedException e) {
	    // this shouldn't happen, since we are Cloneable
	    throw new InternalError();
	}
    
public booleancontains(double x, double y)
Tests if a specified coordinate is inside the boundary of this Line2D. This method is required to implement the {@link Shape} interface, but in the case of Line2D objects it always returns false since a line contains no area.

param
x, y the coordinates of the specified point
return
false because a Line2D contains no area.

	return false;
    
public booleancontains(java.awt.geom.Point2D p)
Tests if a given Point2D is inside the boundary of this Line2D. This method is required to implement the Shape interface, but in the case of Line2D objects it always returns false since a line contains no area.

param
p the specified Point2D to be tested
return
false because a Line2D contains no area.

	return false;
    
public booleancontains(double x, double y, double w, double h)
Tests if the interior of this Line2D entirely contains the specified set of rectangular coordinates. This method is required to implement the Shape interface, but in the case of Line2D objects it always returns false since a line contains no area.

param
x, y the coordinates of the top-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
false because a Line2D contains no area.

	return false;
    
public booleancontains(java.awt.geom.Rectangle2D r)
Tests if the interior of this Line2D entirely contains the specified Rectangle2D. This method is required to implement the Shape interface, but in the case of Line2D objects it always returns false since a line contains no area.

param
r the specified Rectangle2D to be tested
return
false because a Line2D contains no area.

	return false;
    
public java.awt.RectanglegetBounds()
Returns the bounding box of this Line2D.

return
a {@link Rectangle} that is the bounding box of the Line2D.

	return getBounds2D().getBounds();
    
public abstract java.awt.geom.Point2DgetP1()
Returns the starting Point2D of this Line2D.

return
the starting Point2D of this Line2D.

public abstract java.awt.geom.Point2DgetP2()
Returns the end Point2D of this Line2D.

return
a Point2D that is the endpoint of this Line2D.

public java.awt.geom.PathIteratorgetPathIterator(java.awt.geom.AffineTransform at)
Returns an iteration object that defines the boundary of this Line2D. The iterator for this class is not multi-threaded safe, which means that this Line2D class does not guarantee that modifications to the geometry of this Line2D object do not affect any iterations of that geometry that are already in process.

param
at the specified {@link AffineTransform}
return
a {@link PathIterator} that defines the boundary of this Line2D.

	return new LineIterator(this, at);
    
public java.awt.geom.PathIteratorgetPathIterator(java.awt.geom.AffineTransform at, double flatness)
Returns an iteration object that defines the boundary of this flattened Line2D. The iterator for this class is not multi-threaded safe, which means that this Line2D class does not guarantee that modifications to the geometry of this Line2D object do not affect any iterations of that geometry that are already in process.

param
at the specified AffineTransform
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 endpoints. Since a Line2D object is always flat, this parameter is ignored.
return
a PathIterator that defines the boundary of the flattened Line2D

	return new LineIterator(this, at);
    
public abstract doublegetX1()
Returns the X coordinate of the start point in double precision.

return
the X coordinate of this Line2D object's starting point.

public abstract doublegetX2()
Returns the X coordinate of the end point in double precision.

return
the X coordinate of this Line2D object's starting point.

public abstract doublegetY1()
Returns the Y coordinate of the start point in double precision.

return
the Y coordinate of this Line2D object's starting point.

public abstract doublegetY2()
Returns the Y coordinate of the end point in double precision.

return
the Y coordinate of this Line2D object's starting point.

public booleanintersects(double x, double y, double w, double h)
Tests if this Line2D intersects the interior of a specified set of rectangular coordinates.

param
x, y the coordinates of the top-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
true if this Line2D intersects the interior of the specified set of rectangular coordinates; false otherwise.

	return intersects(new Rectangle2D.Double(x, y, w, h));
    
public booleanintersects(java.awt.geom.Rectangle2D r)
Tests if this Line2D intersects the interior of a specified Rectangle2D.

param
r the specified Rectangle2D to be tested
return
true if this Line2D intersects the interior of the specified Rectangle2D; false otherwise.

	return r.intersectsLine(getX1(), getY1(), getX2(), getY2());
    
public booleanintersectsLine(double X1, double Y1, double X2, double Y2)
Tests if the line segment from (X1, Y1) to (X2, Y2) intersects this line segment.

param
X1, Y1 the coordinates of the beginning of the specified line segment
param
X2, Y2 the coordinates of the end of the specified line segment
return
if this line segment and the specified line segment intersect each other; false otherwise.

	return linesIntersect(X1, Y1, X2, Y2,
			      getX1(), getY1(), getX2(), getY2());
    
public booleanintersectsLine(java.awt.geom.Line2D l)
Tests if the specified line segment intersects this line segment.

param
l the specified Line2D
return
true if this line segment and the specified line segment intersect each other; false otherwise.

	return linesIntersect(l.getX1(), l.getY1(), l.getX2(), l.getY2(),
			      getX1(), getY1(), getX2(), getY2());
    
public static booleanlinesIntersect(double X1, double Y1, double X2, double Y2, double X3, double Y3, double X4, double Y4)
Tests if the line segment from (X1, Y1) to (X2, Y2) intersects the line segment from (X3, Y3) to (X4, Y4).

param
X1, Y1 the coordinates of the beginning of the first specified line segment
param
X2, Y2 the coordinates of the end of the first specified line segment
param
X3, Y3 the coordinates of the beginning of the second specified line segment
param
X4, Y4 the coordinates of the end of the second specified line segment
return
true if the first specified line segment and the second specified line segment intersect each other; false otherwise.

	return ((relativeCCW(X1, Y1, X2, Y2, X3, Y3) *
		 relativeCCW(X1, Y1, X2, Y2, X4, Y4) <= 0)
		&& (relativeCCW(X3, Y3, X4, Y4, X1, Y1) *
		    relativeCCW(X3, Y3, X4, Y4, X2, Y2) <= 0));
    
public static doubleptLineDist(double X1, double Y1, double X2, double Y2, double PX, double PY)
Returns the distance from a point to a line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by the specified coordinates. If the specified point intersects the line, this method returns 0.0.

param
X1, Y1 the coordinates of one point on the specified line
param
X2, Y2 the coordinates of another point on the specified line
param
PX, PY the coordinates of the specified point being measured against the specified line
return
a double value that is the distance from the specified point to the specified line.
see
#ptSegDist(double, double, double, double, double, double)

	return Math.sqrt(ptLineDistSq(X1, Y1, X2, Y2, PX, PY));
    
public doubleptLineDist(double PX, double PY)
Returns the distance from a point to this line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by this Line2D. If the specified point intersects the line, this method returns 0.0.

param
PX, PY the coordinates of the specified point being measured against this line
return
a double value that is the distance from a specified point to the current line.
see
#ptSegDist(double, double)

	return ptLineDist(getX1(), getY1(), getX2(), getY2(), PX, PY);
    
public doubleptLineDist(java.awt.geom.Point2D pt)
Returns the distance from a Point2D to this line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by this Line2D. If the specified point intersects the line, this method returns 0.0.

param
pt the specified Point2D being measured
return
a double value that is the distance from a specified Point2D to the current line.
see
#ptSegDist(Point2D)

	return ptLineDist(getX1(), getY1(), getX2(), getY2(),
			 pt.getX(), pt.getY());
    
public static doubleptLineDistSq(double X1, double Y1, double X2, double Y2, double PX, double PY)
Returns the square of the distance from a point to a line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by the specified coordinates. If the specified point intersects the line, this method returns 0.0.

param
X1, Y1 the coordinates of one point on the specified line
param
X2, Y2 the coordinates of another point on the specified line
param
PX, PY the coordinates of the specified point being measured against the specified line
return
a double value that is the square of the distance from the specified point to the specified line.
see
#ptSegDistSq(double, double, double, double, double, double)

	// Adjust vectors relative to X1,Y1
	// X2,Y2 becomes relative vector from X1,Y1 to end of segment
	X2 -= X1;
	Y2 -= Y1;
	// PX,PY becomes relative vector from X1,Y1 to test point
	PX -= X1;
	PY -= Y1;
	double dotprod = PX * X2 + PY * Y2;
	// dotprod is the length of the PX,PY vector
	// projected on the X1,Y1=>X2,Y2 vector times the
	// length of the X1,Y1=>X2,Y2 vector
	double projlenSq = dotprod * dotprod / (X2 * X2 + Y2 * Y2);
	// Distance to line is now the length of the relative point
	// vector minus the length of its projection onto the line
	double lenSq = PX * PX + PY * PY - projlenSq;
	if (lenSq < 0) {
	    lenSq = 0;
	}
	return lenSq;
    
public doubleptLineDistSq(double PX, double PY)
Returns the square of the distance from a point to this line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by this Line2D. If the specified point intersects the line, this method returns 0.0.

param
PX, PY the coordinates of the specified point being measured against this line
return
a double value that is the square of the distance from a specified point to the current line.
see
#ptSegDistSq(double, double)

	return ptLineDistSq(getX1(), getY1(), getX2(), getY2(), PX, PY);
    
public doubleptLineDistSq(java.awt.geom.Point2D pt)
Returns the square of the distance from a specified Point2D to this line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by this Line2D. If the specified point intersects the line, this method returns 0.0.

param
pt the specified Point2D being measured against this line
return
a double value that is the square of the distance from a specified Point2D to the current line.
see
#ptSegDistSq(Point2D)

	return ptLineDistSq(getX1(), getY1(), getX2(), getY2(),
			    pt.getX(), pt.getY());
    
public static doubleptSegDist(double X1, double Y1, double X2, double Y2, double PX, double PY)
Returns the distance from a point to a line segment. The distance measured is the distance between the specified point and the closest point between the specified endpoints. If the specified point intersects the line segment in between the endpoints, this method returns 0.0.

param
X1, Y1 the coordinates of the beginning of the specified line segment
param
X2, Y2 the coordinates of the end of the specified line segment
param
PX, PY the coordinates of the specified point being measured against the specified line segment
return
a double value that is the distance from the specified point to the specified line segment.
see
#ptLineDist(double, double, double, double, double, double)

	return Math.sqrt(ptSegDistSq(X1, Y1, X2, Y2, PX, PY));
    
public doubleptSegDist(double PX, double PY)
Returns the distance from a point to this line segment. The distance measured is the distance between the specified point and the closest point between the current line's endpoints. If the specified point intersects the line segment in between the endpoints, this method returns 0.0.

param
PX, PY the coordinates of the specified point being measured against this line segment
return
a double value that is the distance from the specified point to the current line segment.
see
#ptLineDist(double, double)

	return ptSegDist(getX1(), getY1(), getX2(), getY2(), PX, PY);
    
public doubleptSegDist(java.awt.geom.Point2D pt)
Returns the distance from a Point2D to this line segment. The distance measured is the distance between the specified point and the closest point between the current line's endpoints. If the specified point intersects the line segment in between the endpoints, this method returns 0.0.

param
pt the specified Point2D being measured against this line segment
return
a double value that is the distance from the specified Point2D to the current line segment.
see
#ptLineDist(Point2D)

	return ptSegDist(getX1(), getY1(), getX2(), getY2(),
			 pt.getX(), pt.getY());
    
public static doubleptSegDistSq(double X1, double Y1, double X2, double Y2, double PX, double PY)
Returns the square of the distance from a point to a line segment. The distance measured is the distance between the specified point and the closest point between the specified endpoints. If the specified point intersects the line segment in between the endpoints, this method returns 0.0.

param
X1, Y1 the coordinates of the beginning of the specified line segment
param
X2, Y2 the coordinates of the end of the specified line segment
param
PX, PY the coordinates of the specified point being measured against the specified line segment
return
a double value that is the square of the distance from the specified point to the specified line segment.
see
#ptLineDistSq(double, double, double, double, double, double)

	// Adjust vectors relative to X1,Y1
	// X2,Y2 becomes relative vector from X1,Y1 to end of segment
	X2 -= X1;
	Y2 -= Y1;
	// PX,PY becomes relative vector from X1,Y1 to test point
	PX -= X1;
	PY -= Y1;
	double dotprod = PX * X2 + PY * Y2;
	double projlenSq;
	if (dotprod <= 0.0) {
	    // PX,PY is on the side of X1,Y1 away from X2,Y2
	    // distance to segment is length of PX,PY vector
	    // "length of its (clipped) projection" is now 0.0
	    projlenSq = 0.0;
	} else {
	    // switch to backwards vectors relative to X2,Y2
	    // X2,Y2 are already the negative of X1,Y1=>X2,Y2
	    // to get PX,PY to be the negative of PX,PY=>X2,Y2
	    // the dot product of two negated vectors is the same
	    // as the dot product of the two normal vectors
	    PX = X2 - PX;
	    PY = Y2 - PY;
	    dotprod = PX * X2 + PY * Y2;
	    if (dotprod <= 0.0) {
		// PX,PY is on the side of X2,Y2 away from X1,Y1
		// distance to segment is length of (backwards) PX,PY vector
		// "length of its (clipped) projection" is now 0.0
		projlenSq = 0.0;
	    } else {
		// PX,PY is between X1,Y1 and X2,Y2
		// dotprod is the length of the PX,PY vector
		// projected on the X2,Y2=>X1,Y1 vector times the
		// length of the X2,Y2=>X1,Y1 vector
		projlenSq = dotprod * dotprod / (X2 * X2 + Y2 * Y2);
	    }
	}
	// Distance to line is now the length of the relative point
	// vector minus the length of its projection onto the line
	// (which is zero if the projection falls outside the range
	//  of the line segment).
	double lenSq = PX * PX + PY * PY - projlenSq;
	if (lenSq < 0) {
	    lenSq = 0;
	}
	return lenSq;
    
public doubleptSegDistSq(double PX, double PY)
Returns the square of the distance from a point to this line segment. The distance measured is the distance between the specified point and the closest point between the current line's endpoints. If the specified point intersects the line segment in between the endpoints, this method returns 0.0.

param
PX, PY the coordinates of the specified point being measured against this line segment
return
a double value that is the square of the distance from the specified point to the current line segment.
see
#ptLineDistSq(double, double)

	return ptSegDistSq(getX1(), getY1(), getX2(), getY2(), PX, PY);
    
public doubleptSegDistSq(java.awt.geom.Point2D pt)
Returns the square of the distance from a Point2D to this line segment. The distance measured is the distance between the specified point and the closest point between the current line's endpoints. If the specified point intersects the line segment in between the endpoints, this method returns 0.0.

param
pt the specified Point2D being measured against this line segment.
return
a double value that is the square of the distance from the specified Point2D to the current line segment.
see
#ptLineDistSq(Point2D)

	return ptSegDistSq(getX1(), getY1(), getX2(), getY2(),
			   pt.getX(), pt.getY());
    
public static intrelativeCCW(double X1, double Y1, double X2, double Y2, double PX, double PY)
Returns an indicator of where the specified point (PX, PY) lies with respect to the line segment from (X1, Y1) to (X2, Y2). The return value can be either 1, -1, or 0 and indicates in which direction the specified line must pivot around its first endpoint, (X1, Y1), in order to point at the specified point (PX, PY).

A return value of 1 indicates that the line segment must turn in the direction that takes the positive X axis towards the negative Y axis. In the default coordinate system used by Java 2D, this direction is counterclockwise.

A return value of -1 indicates that the line segment must turn in the direction that takes the positive X axis towards the positive Y axis. In the default coordinate system, this direction is clockwise.

A return value of 0 indicates that the point lies exactly on the line segment. Note that an indicator value of 0 is rare and not useful for determining colinearity because of floating point rounding issues.

If the point is colinear with the line segment, but not between the endpoints, then the value will be -1 if the point lies "beyond (X1, Y1)" or 1 if the point lies "beyond (X2, Y2)".

param
X1, Y1 the coordinates of the beginning of the specified line segment
param
X2, Y2 the coordinates of the end of the specified line segment
param
PX, PY the coordinates of the specified point to be compared with the specified line segment
return
an integer that indicates the position of the third specified coordinates with respect to the line segment formed by the first two specified coordinates.

	X2 -= X1;
	Y2 -= Y1;
	PX -= X1;
	PY -= Y1;
	double ccw = PX * Y2 - PY * X2;
	if (ccw == 0.0) {
	    // The point is colinear, classify based on which side of
	    // the segment the point falls on.  We can calculate a
	    // relative value using the projection of PX,PY onto the
	    // segment - a negative value indicates the point projects
	    // outside of the segment in the direction of the particular
	    // endpoint used as the origin for the projection.
	    ccw = PX * X2 + PY * Y2;
	    if (ccw > 0.0) {
		// Reverse the projection to be relative to the original X2,Y2
		// X2 and Y2 are simply negated.
		// PX and PY need to have (X2 - X1) or (Y2 - Y1) subtracted
		//    from them (based on the original values)
		// Since we really want to get a positive answer when the
		//    point is "beyond (X2,Y2)", then we want to calculate
		//    the inverse anyway - thus we leave X2 & Y2 negated.
		PX -= X2;
		PY -= Y2;
		ccw = PX * X2 + PY * Y2;
		if (ccw < 0.0) {
		    ccw = 0.0;
		}
	    }
	}
	return (ccw < 0.0) ? -1 : ((ccw > 0.0) ? 1 : 0);
    
public intrelativeCCW(double PX, double PY)
Returns an indicator of where the specified point (PX, PY) lies with respect to this line segment. See the method comments of {@link #relativeCCW(double, double, double, double, double, double)} to interpret the return value.

param
PX, PY the coordinates of the specified point to be compared with the current line segment
return
an integer that indicates the position of the specified coordinates with respect to the current line segment.
see
#relativeCCW(double, double, double, double, double, double)

	return relativeCCW(getX1(), getY1(), getX2(), getY2(), PX, PY);
    
public intrelativeCCW(java.awt.geom.Point2D p)
Returns an indicator of where the specified Point2D lies with respect to this line segment. See the method comments of {@link #relativeCCW(double, double, double, double, double, double)} to interpret the return value.

param
p the specified Point2D to be compared with the current line segment
return
an integer that indicates the position of the Point2D with respect to the current line segment.
see
#relativeCCW(double, double, double, double, double, double)

	return relativeCCW(getX1(), getY1(), getX2(), getY2(),
			   p.getX(), p.getY());
    
public voidsetLine(java.awt.geom.Line2D l)
Sets the location of the endpoints of this Line2D to the same as those endpoints of the specified Line2D.

param
l the specified Line2D

	setLine(l.getX1(), l.getY1(), l.getX2(), l.getY2());
    
public abstract voidsetLine(double X1, double Y1, double X2, double Y2)
Sets the location of the endpoints of this Line2D to the specified double coordinates.

param
X1, Y1 the first specified coordinate
param
X2, Y2 the second specified coordinate

public voidsetLine(java.awt.geom.Point2D p1, java.awt.geom.Point2D p2)
Sets the location of the endpoints of this Line2D to the specified Point2D coordinates.

param
p1, p2 the specified Point2D objects

	setLine(p1.getX(), p1.getY(), p2.getX(), p2.getY());