Creating Windows - Beginning Java - page 821

You can also use several methods to combine Rectangle objects and to extend a Rectangle object to
enclose a point. The effects of each of these methods are shown in Figure 17-8 .
FIGURE 17-8
The rectangle that results from each operation is shown with dashed line boundaries. The details of the
operations provided by the methods illustrated in Figure 17-8 are as follows:
• Rectangle intersection(Rectangle r) : Returns a Rectangle object that is the intersection of
the current object and the argument. If the two rectangles do not intersect, the Rectangle object
returned is at position (0,0), and the width and height members are zero, so the rectangle is
empty.
• Rectangle union(Rectangle r) : Returns the smallest Rectangle object enclosing both the cur-
rent Rectangle object and the Rectangle object r, passed as an argument.
• void add(Rectangle r) : Expands the current Rectangle object to enclose the argument Rect-
angle .
• void add(Point p) : Expands the current Rectangle object to enclose the Point object p . The
result is the smallest rectangle that encloses the original rectangle and the point.
• void add(int x, int y) : Expands the current Rectangle object to enclose the point at ( x , y ).
• void grow(int h, int v) : Enlarges the current Rectangle object by moving the boundary out
from the center by h horizontally and v vertically.
You can also test and compare Rectangle objects in various ways with the following methods:
• boolean isEmpty() : Returns true if the width and height members of the current Rectangle
object are zero and returns false otherwise.
• boolean equals(Object rect) : Returns true if the Rectangle object passed as an argument is
equal to the current Rectangle object, and false otherwise. The two rectangles are equal if they
are at the same position and have the same width and height. If the argument is not a Rectangle
object, false is returned.
• boolean intersects(Rectangle rect) : Returns true if the current Rectangle object intersects
rect and returns false otherwise.
• boolean contains(Point p) : Returns true if the current Rectangle object encloses p and re-
turns false otherwise.