What happens when we pass int arguments to the ove

问题:

In overloading concept, i am having one doubt, that is . when i comes to overload the method with int value the method call's the float parameter method rather the double parameter method.

void method1(float f){
System.out.println('float');
}

void method1(double f){
System.out.println('double');
}

method call:

method1(10);

output: float

As stated in the java tutorials in this link A floating-point literal is of type float if it ends with the letter F or f; otherwise its type is double and it can optionally end with the letter D or d.

For the above case the method call should call the double parameter method. But it call's float parameter method.

How the process of overloading taking place in this area?.

回答1:

Testing a variant of your code, except with a byte literal and overloaded methods with various combinations of short, int, and long appears to imply that the compiler chooses the "least widening" conversion if more than one is available.

Thus:

• Between a short and an int, if you call the overloaded method with a byte, the short variant will be chosen
• Between an int and a long, if you call the overloaded method with a byte or short, the int variant will be chosen

And so forth.

Thus, because long can be widened to either float or double, and because the float conversion is the "least widening", the float overload is chosen.

---

I think this is because of the "choose the most specific overload" way that the compiler resolves multiple possible overloads. From the JLS, section 15.12.2.5:

The informal intuition is that one method is more specific than another if any invocation handled by the first method could be passed on to the other one without a compile-time error.

So by this, a method that takes a float is "more specific" than a method that takes a double because any invocation handled by a method that takes a float can always be handled by a method that takes a double, but not the other way around.

回答2:

as per http://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html

5.1.2. Widening Primitive Conversion

19 specific conversions on primitive types are called the widening primitive conversions:

byte to short, int, long, float, or double

short to int, long, float, or double

char to int, long, float, or double

int to long, float, or double

long to float or double

float to double

回答3:

In Java,there is relation between sub class and super class and also ascending level for primitives from byte short.... to double.

The rule is, whenever there is ambiguity which overloaded method to choose, the most near one sub class overloaded method or nearest primitive in ascending order is chosen.