The Java Language Specification, Third Edition

EXPRESSIONS Compile-Time Step 2: Determine Method Signature 15.12.2
public static long two(long j) {return j+j; }
public static void main(String[] args) {
System.out.println(two(3));
System.out.println(Doubler.two(3)); // compile-time error
}
}
for the method invocation two(1) within class Doubler, there are two accessible
methods named two, but only the second one is applicable, and so that is the one
invoked at run time. For the method invocation two(3) within class Test, there
are two applicable methods, but only the one in class Test is accessible, and so
that is the one to be invoked at run time (the argument 3 is converted to type
long). For the method invocation Doubler.two(3), the class Doubler, not class
Test, is searched for methods named two; the only applicable method is not
accessible, and so this method invocation causes a compile-time error.
Another example is:
class ColoredPoint {
int x, y;
byte color;
void setColor(byte color) { this.color = color; }
}
class Test {
public static void main(String[] args) {
ColoredPoint cp = new ColoredPoint();
byte color = 37;
cp.setColor(color);
cp.setColor(37); // compile-time error
}
}
Here, a compile-time error occurs for the second invocation of setColor, because
no applicable method can be found at compile time. The type of the literal 37 is
int, and int cannot be converted to byte by method invocation conversion.
Assignment conversion, which is used in the initialization of the variable color,
performs an implicit conversion of the constant from type int to byte, which is
permitted because the value 37 is small enough to be represented in type byte;but
such a conversion is not allowed for method invocation conversion.
If the method setColor had, however, been declared to take an int instead of
a byte, then both method invocations would be correct; the first invocation would
be allowed because method invocation conversion does permit a widening conversion
from byte to int. However, a narrowing cast would then be required in the
body of setColor:
void setColor(int color) { this.color = (byte)color; }
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