OverLoading Question

[Sarma Lolla]

class base{
void func(int i){System.out.println("int");}
}
class derived extends base{
void func(float i){System.out.println("float");}
public static void main(String args[]){
derived d1 = new derived();
int i = 30;
d1.func(i);
}
}

[Sarma Lolla]

In the above question why am I getting comiler error?

[tony kanvas]

try this link may be will help you

  [url=https://coderanch.com/t/240554/java-programmer-SCJP/certification/conversion-long-float

]https://coderanch.com/t/240554/java-programmer-SCJP/certification/conversion-long-float[/CODE][/url]

[chi Lin]

Tony,
the link does not seems to work.

Originally posted by tony kanvas:
try this link may be will help you

  [url=https://coderanch.com/t/240554/java-programmer-SCJP/certification/conversion-long-float

]https://coderanch.com/t/240554/java-programmer-SCJP/certification/conversion-long-float[/code][/url]

[Claire Yang]

Sarma, I rearranged your code:

class base {
void func(int i) {
System.out.println("int");
}
} 
class derived extends base {
void func(float i) {
System.out.println("float");
} 
public static void main(String args[]) { 
derived d1 = new derived(); 
int i = 30;
d1.func(i);
}
} 

Mehtod func in derived "override" method func in base, not "overload". When you override parent's method, you should note five items: the same return type, the smae method name, the same arguments list, more visibility(e.g. you can't override public method with protected method) and throw the subset exception of the parent's exception if needed. Hope this helps.

[chi Lin]

Sarma,
my two cents :
parameter-wise, the "int" method in base is more specific
// it takes 'int' as argument
hierarchy-wise, the "float" methid in derived is more specific
// it is defined in derived
So compiler has difficulty figure out which one to use
You can try two things to ease compiler's confusion,
1. swap position of the methods -> "int" in derived, "float" in base
2. put both methods in same clase (base or derived).
hope this help

[Claire Yang]

Chi, you're right, Sarma asked about overload--not override,

[Sarma Lolla]

tony,
Can you give me correct link if that has some useful info that clears my doubts on overloading/overriding
Claire,
I am overloading the function here. I am not overriding it. I have changed my argument type in derived class so the overriding question shouldn't arise. How ever your five points are very clear and to the point for overriding case.
chi,
How can we solve these questions if they appear in Exam? Is there any rule how to resolve in these cases? I never thought that the compiler would look for a function which is taking a float as parameter when I already defined a function with int param and calling the function with int param.

[chi Lin]

Sarma,
I believe Tony refer to the link below,
// copy & paste the whole link should be OK
https://coderanch.com/t/240554/java-programmer-SCJP/certification/conversion-long-float
For other Qs you asked, I am afraid I won't be able to answer them fully/correctly.

[Jose Botella]

The rule of JLS 15.12.2.2 Choosing the most specific method tells us that the type of the classes in which the methods are declared must also be considered. Do not consider only the parameters:
Base.func(int) --> one point, the parameter int is more specific than float.
Derived.func(float) --> one point, it is declared within Derived, which is more specific than Base.
Thus there is a draw and the method call d1.func(i) is ambigous.

[Mellihoney Michael]

class base{
void func(int i){System.out.println("int");}
}
class derived extends base{
void func(float i){System.out.println("float");}
public static void main(String args[]){
derived d1 = new derived();
float i = 30;
d1.func(i);
}
}

does above compiled without error?

[Sridhar Srikanthan]

Yes it will and print float as answer.
Because, you have taken a float argument and the matching method in the "derived" class itself.
Thanks
Sri

[Jasper Vader]

i thought it might not matter if an overriden method's return type was different?

Originally posted by Claire Yang:
When you override parent's method, you should note five items: the same return type, the smae method name, the same arguments list, more visibility(e.g. you can't override public method with protected method) and throw the subset exception of the parent's exception if needed. Hope this helps.

[Mellihoney Michael]

class base{
void func(int i){System.out.println("int");}
}
class derived extends base{
void func(float i){System.out.println("float");}
public static void main(String args[]){
derived d1 = new derived();
int i = 30;
d1.func((float)i);
}
}
if this is complied, you can find the answer!

[Sarma Lolla]

Melliholic Michael,
In your example you didn't override any method. You just over loaded the methods. That is why you could change your return types for the methods.