8.4.8

Examples of Method Declarations

CLASSES

class Point {

int x = 0, y = 0;

void move(int dx, int dy) { x += dx; y += dy; }

int getX() { return x; }

int getY() { return y; }

int color;

}

class RealPoint extends Point {

float x = 0.0f, y = 0.0f;

void move(int dx, int dy) { move((float)dx, (float)dy); }

void move(float dx, float dy) { x += dx; y += dy; }

int getX() { return (int)Math.floor(x); }

int getY() { return (int)Math.floor(y); }

}

Here the overriding methods

getX

 and

getY

 in class

RealPoint

 have the same

return types as the methods of class

Point

 that they override, so this code can be

successfully compiled.

Consider, then, this test program:

class Test {

public static void main(String[] args) {

RealPoint rp = new RealPoint();

Point p = rp;

rp.move(1.71828f, 4.14159f);

p.move(1,  1);

show(p.x, p.y);

show(rp.x, rp.y);

show(p.getX(), p.getY());

show(rp.getX(), rp.getY());

}

static void show(int x, int y) {

System.out.println("(" + x + ", " + y + ")");

}

static void show(float x, float y) {

System.out.println("(" + x + ", " + y + ")");

}

}

The output from this program is:

170