Examples of Useful Java Classes

(pre-defined)

class Rectangle

• represents rectangular area on plane
• not a graphic object as such, but can be used with graphics

Fields

  int x;      ˆ

  int y;      ˜    all are accessible

  int width;  ˜    as public variables

  int height; ¯

Rectangle Constructors

Rectangle(int x, int y, int width, int height)

Rectangle(int width, int height)  //x=y=0

Rectangle()  //x=y=width=height=0

3 others

Note:  No Rectangle(int x, int y)

Why?

Rectangle methods  (partial list)

• void resize(int width, int height)
• void reshape(int x, int y, int width, int height)
• void move(int x, int y)
• void add(int x, int y)

Enlarge rectangle, if necessary, to include point x,y

• void add(Rectangle r)

Enlarge to include r

• boolean inside(int x, int y)

Asks whether point x,y is inside this rectangle.

• void translate(int dx, int dy)

Move by dx, dy