Polygonpublic class Polygon extends Object implements Shape, SerializableThe 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 {@code (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 {@code (x,y)} points are joined by a line segment
that closes the polygon. This Polygon is defined with
an even-odd winding rule. See
{@link java.awt.geom.PathIterator#WIND_EVEN_ODD 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
{@link Shape} class comments. |
| Fields Summary |
|---|
| public int | npointsThe 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
{@link #xpoints xpoints} or {@link #ypoints ypoints}.
This value can be NULL. | | public int[] | xpointsThe 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 {@link #npoints npoints} is equal to the
number of valid points in this Polygon. | | public int[] | ypointsThe 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. | | protected Rectangle | boundsThe bounds of this {@code Polygon}.
This value can be null. | | private static final long | serialVersionUID | | private static final int | MIN_LENGTH |
| Constructors Summary |
|---|
public Polygon()Creates an empty polygon.
xpoints = new int[MIN_LENGTH];
ypoints = new int[MIN_LENGTH];
| public Polygon(int[] xpoints, int[] ypoints, int npoints)Constructs and initializes a Polygon from the specified
parameters.
// Fix 4489009: should throw IndexOutofBoundsException instead
// of OutofMemoryException if npoints is huge and > {x,y}points.length
if (npoints > xpoints.length || npoints > ypoints.length) {
throw new IndexOutOfBoundsException("npoints > xpoints.length || "+
"npoints > ypoints.length");
}
// Fix 6191114: should throw NegativeArraySizeException with
// negative npoints
if (npoints < 0) {
throw new NegativeArraySizeException("npoints < 0");
}
// Fix 6343431: Applet compatibility problems if arrays are not
// exactly npoints in length
this.npoints = npoints;
this.xpoints = Arrays.copyOf(xpoints, npoints);
this.ypoints = Arrays.copyOf(ypoints, npoints);
|
| Methods Summary |
|---|
| 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.
if (npoints >= xpoints.length || npoints >= ypoints.length) {
int newLength = npoints * 2;
// Make sure that newLength will be greater than MIN_LENGTH and
// aligned to the power of 2
if (newLength < MIN_LENGTH) {
newLength = MIN_LENGTH;
} else if ((newLength & (newLength - 1)) != 0) {
newLength = Integer.highestOneBit(newLength);
}
xpoints = Arrays.copyOf(xpoints, newLength);
ypoints = Arrays.copyOf(ypoints, newLength);
}
xpoints[npoints] = x;
ypoints[npoints] = y;
npoints++;
if (bounds != null) {
updateBounds(x, y);
}
| | void | calculateBounds(int[] xpoints, int[] ypoints, int npoints)
int boundsMinX = Integer.MAX_VALUE;
int boundsMinY = Integer.MAX_VALUE;
int boundsMaxX = Integer.MIN_VALUE;
int boundsMaxY = Integer.MIN_VALUE;
for (int i = 0; i < npoints; i++) {
int x = xpoints[i];
boundsMinX = Math.min(boundsMinX, x);
boundsMaxX = Math.max(boundsMaxX, x);
int y = ypoints[i];
boundsMinY = Math.min(boundsMinY, y);
boundsMaxY = Math.max(boundsMaxY, y);
}
bounds = new Rectangle(boundsMinX, boundsMinY,
boundsMaxX - boundsMinX,
boundsMaxY - boundsMinY);
| | public boolean | contains(java.awt.Point p)Determines whether the specified {@link Point} is inside this
Polygon.
return contains(p.x, p.y);
| | public boolean | contains(int x, int y)Determines whether the specified coordinates are inside this
Polygon.
return contains((double) x, (double) y);
| | public boolean | contains(double x, double y){@inheritDoc}
if (npoints <= 2 || !getBoundingBox().contains(x, y)) {
return false;
}
int hits = 0;
int lastx = xpoints[npoints - 1];
int lasty = ypoints[npoints - 1];
int curx, cury;
// Walk the edges of the polygon
for (int i = 0; i < npoints; lastx = curx, lasty = cury, i++) {
curx = xpoints[i];
cury = ypoints[i];
if (cury == lasty) {
continue;
}
int leftx;
if (curx < lastx) {
if (x >= lastx) {
continue;
}
leftx = curx;
} else {
if (x >= curx) {
continue;
}
leftx = lastx;
}
double test1, test2;
if (cury < lasty) {
if (y < cury || y >= lasty) {
continue;
}
if (x < leftx) {
hits++;
continue;
}
test1 = x - curx;
test2 = y - cury;
} else {
if (y < lasty || y >= cury) {
continue;
}
if (x < leftx) {
hits++;
continue;
}
test1 = x - lastx;
test2 = y - lasty;
}
if (test1 < (test2 / (lasty - cury) * (lastx - curx))) {
hits++;
}
}
return ((hits & 1) != 0);
| | public boolean | contains(java.awt.geom.Point2D p){@inheritDoc}
return contains(p.getX(), p.getY());
| | public boolean | contains(double x, double y, double w, double h){@inheritDoc}
if (npoints <= 0 || !getBoundingBox().intersects(x, y, w, h)) {
return false;
}
Crossings cross = getCrossings(x, y, x+w, y+h);
return (cross != null && cross.covers(y, y+h));
| | public boolean | contains(java.awt.geom.Rectangle2D r){@inheritDoc}
return contains(r.getX(), r.getY(), r.getWidth(), r.getHeight());
| | public java.awt.Rectangle | getBoundingBox()Returns the bounds of this Polygon.
if (npoints == 0) {
return new Rectangle();
}
if (bounds == null) {
calculateBounds(xpoints, ypoints, npoints);
}
return bounds.getBounds();
| | public java.awt.Rectangle | getBounds()Gets the bounding box of this Polygon.
The bounding box is the smallest {@link Rectangle} whose
sides are parallel to the x and y axes of the
coordinate space, and can completely contain the Polygon.
return getBoundingBox();
| | public java.awt.geom.Rectangle2D | getBounds2D(){@inheritDoc}
return getBounds();
| | private sun.awt.geom.Crossings | getCrossings(double xlo, double ylo, double xhi, double yhi)
Crossings cross = new Crossings.EvenOdd(xlo, ylo, xhi, yhi);
int lastx = xpoints[npoints - 1];
int lasty = ypoints[npoints - 1];
int curx, cury;
// Walk the edges of the polygon
for (int i = 0; i < npoints; i++) {
curx = xpoints[i];
cury = ypoints[i];
if (cross.accumulateLine(lastx, lasty, curx, cury)) {
return null;
}
lastx = curx;
lasty = cury;
}
return cross;
| | public java.awt.geom.PathIterator | getPathIterator(java.awt.geom.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
{@link AffineTransform} can be specified so that the coordinates
returned in the iteration are transformed accordingly.
return new PolygonPathIterator(this, at);
| | public java.awt.geom.PathIterator | getPathIterator(java.awt.geom.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.
return getPathIterator(at);
| | public boolean | inside(int x, int y)Determines whether the specified coordinates are contained in this
Polygon.
return contains((double) x, (double) y);
| | public boolean | intersects(double x, double y, double w, double h){@inheritDoc}
if (npoints <= 0 || !getBoundingBox().intersects(x, y, w, h)) {
return false;
}
Crossings cross = getCrossings(x, y, x+w, y+h);
return (cross == null || !cross.isEmpty());
| | public boolean | intersects(java.awt.geom.Rectangle2D r){@inheritDoc}
return intersects(r.getX(), r.getY(), r.getWidth(), r.getHeight());
| | 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.
bounds = null;
| | 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.
npoints = 0;
bounds = null;
| | 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.
for (int i = 0; i < npoints; i++) {
xpoints[i] += deltaX;
ypoints[i] += deltaY;
}
if (bounds != null) {
bounds.translate(deltaX, deltaY);
}
| | void | updateBounds(int x, int y)
if (x < bounds.x) {
bounds.width = bounds.width + (bounds.x - x);
bounds.x = x;
}
else {
bounds.width = Math.max(bounds.width, x - bounds.x);
// bounds.x = bounds.x;
}
if (y < bounds.y) {
bounds.height = bounds.height + (bounds.y - y);
bounds.y = y;
}
else {
bounds.height = Math.max(bounds.height, y - bounds.y);
// bounds.y = bounds.y;
}
|
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