15.11.2

Compile Time Step 2: Determine Method Signature

EXPRESSIONS

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 spe 

cific 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.

15.11.2.4

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 color;

}

static String test(Point p) {

return "Point";

}

public static void main(String[] args) {

ColoredPoint cp = new ColoredPoint();

String s = test(cp);

//

compile time error

}

}

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