The Java Language Specification, Third Edition

15.12.2 Compile-Time Step 2: Determine Method Signature EXPRESSIONS
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15.12.2.10 Example: Overloading Ambiguity
Consider the example:
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.
DRAFT
15.12.2.11 Example: Return Type Not Considered
As another example, consider:
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) {