Rectangle specifies an area in a coordinate space that isenclosed by the
Rectangle object’s upper-left point(x,y)in the coordinate space, its width, and its height.
specifies an area in a coordinate space that is enclosed by theobject’s upper-left pointin the coordinate space, its width, and its height.
A Rectangle object’s width and
height are public fields. The constructors
that create a Rectangle, and the methods that can modify
one, do not prevent setting a negative value for width or height.
A Rectangle whose width or height is exactly zero has location
along those axes with zero dimension, but is otherwise considered empty.
The isEmpty() method will return true for such a Rectangle.
Methods which test if an empty Rectangle contains or intersects
a point or rectangle will always return false if either dimension is zero.
Methods which combine such a Rectangle with a point or rectangle
will include the location of the Rectangle on that axis in the
result as if the add(Point) method were being called.
A Rectangle whose width or height is negative has neither
location nor dimension along those axes with negative dimensions.
Such a Rectangle is treated as non-existant along those axes.
Such a Rectangle is also empty with respect to containment
calculations and methods which test if it contains or intersects a
point or rectangle will always return false.
Methods which combine such a Rectangle with a point or rectangle
will ignore the Rectangle entirely in generating the result.
If two Rectangle objects are combined and each has a negative
dimension, the result will have at least one negative dimension.
Methods which affect only the location of a Rectangle will
operate on its location regardless of whether or not it has a negative
or zero dimension along either axis.
Note that a Rectangle constructed with the default no-argument
constructor will have dimensions of 0x0 and therefore be empty.
That Rectangle will still have a location of (0,0) and
will contribute that location to the union and add operations.
Code attempting to accumulate the bounds of a set of points should
therefore initially construct the Rectangle with a specifically
negative width and height or it should use the first point in the set
to construct the Rectangle.
For example:
Rectangle bounds = new Rectangle(0, 0, -1, -1);
for (int i = 0; i < points.length; i++) {
bounds.add(points[i]);
}
or if we know that the points array contains at least one point:
Rectangle bounds = new Rectangle(points[0]);
for (int i = 1; i < points.length; i++) {
bounds.add(points[i]);
}
or if we know that the points array contains at least one point:
This class uses 32-bit integers to store its location and dimensions.
Frequently operations may produce a result that exceeds the range of
a 32-bit integer.
The methods will calculate their results in a way that avoids any
32-bit overflow for intermediate results and then choose the best
representation to store the final results back into the 32-bit fields
which hold the location and dimensions.
The location of the result will be stored into the x and
y fields by clipping the true result to the nearest 32-bit value.
The values stored into the width and height dimension
fields will be chosen as the 32-bit values that encompass the largest
part of the true result as possible.
Generally this means that the dimension will be clipped independently
to the range of 32-bit integers except that if the location had to be
moved to store it into its pair of 32-bit fields then the dimensions
will be adjusted relative to the “best representation” of the location.
If the true result had a negative dimension and was therefore
non-existant along one or both axes, the stored dimensions will be
negative numbers in those axes.
If the true result had a location that could be represented within
the range of 32-bit integers, but zero dimension along one or both
axes, then the stored dimensions will be zero in those axes.
