Java Reference
In-Depth Information
class Point { int x, y; }
class ColoredPoint extends Point { int color; }
class Test {
static void test(ColoredPoint p, Point q) {
System.out.println("(ColoredPoint, Point)");
}
static void test(Point p, ColoredPoint q) {
System.out.println("(Point, ColoredPoint)");
}
public static void main(String[] args) {
ColoredPoint cp = new ColoredPoint();
test(cp, cp); // compile-time error
}
}
This example produces an error at compile time. The problem is that there are two
declarations of
test
that are applicable and accessible, and neither is more specific than
the other. Therefore, the method invocation is ambiguous.
If a third definition of
test
were added:
static void test(ColoredPoint p, ColoredPoint q) {
System.out.println("(ColoredPoint, ColoredPoint)");
}
then it would be more specific than the other two, and the method invocation would
no longer be ambiguous.
Example 15.12.2-2. Return Type Not Considered During Method Selection
class Point { int x, y; }
class ColoredPoint extends Point { int color; }
class Test {
static int test(ColoredPoint p) {
return p.color;
}
static String test(Point p) {
return "Point";
}
public static void main(String[] args) {
ColoredPoint cp = new ColoredPoint();
