Get rid of Unchecked overriding: return type requires unchecked conversion
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Get rid of Unchecked overriding: return type requires unchecked conversion
Example code similar to my code.
public interface Builder<B, A> {
B build(A a);
}
public class ClientBuilder implements Builder<String, Integer> {
@Override
public String build(Integer i) {
return i.toString();
}
}
public abstract class Client<B> {
protected abstract <A> Builder<B, A> getBuilder();
}
public class ClientClient extends Client<String> {
@Override
protected Builder<String, Integer> getBuilder() {
return null;
}
}
In my ClientClient class I get a warning that says the following:
ClientClient
Unchecked overriding: return type requires unchecked conversion.Found 'Builder<java.lang.String,java.lang.Integer>', required 'Builder<java.lang.String,A>
Unchecked overriding: return type requires unchecked conversion.Found 'Builder<java.lang.String,java.lang.Integer>', required 'Builder<java.lang.String,A>
Is there something I can do to get rid of this error?
I could use @SuppressWarnings("unchecked"), but that doesn't feel right.
@SuppressWarnings("unchecked")
In my example A is always an Integer but in my real code A can be one of two objects.
A
Integer
A
I guess I could also have two methods in my interface like this:
public interface Builder<B> {
B build(Integer i);
B build(String s);
}
Function<A,B>
The compiler does not lie here,
<A>is not the type from Builder<B, A>, but any type passed to the method.– Glains
6 hours ago
<A>
Builder<B, A>
1 Answer
1
This isn't overriding the method correctly:
protected Builder<String, Integer> getBuilder() {
return null;
}
You're missing the type variable.
Either declare it correctly:
protected <A> Builder<String, A> getBuilder() {
return null;
}
or change the class declaration to allow you to provide the second type parameter:
public abstract class Client<B, A> {
protected abstract Builder<B, A> getBuilder();
}
I have tried that but the issue that occurs is that I cant access the getters from A
– idkwat2do
6 hours ago
There are no getters from A, aside from those on
Object. If you want your getBuilder() method to access methods specific to Integer, you would need to add the extra type parameter to the class.– Andy Turner
5 hours ago
Object
getBuilder()
Integer
I can not seem to get around it. I've tried both ways but I end up having to access getters of A.. Would using
@SuppressWarnings be "ok" at this point or should I add another method to the interface which leads to the affected classes having to implement a method that will do nothing expect for the one class where it will be used and vice versa.– idkwat2do
5 hours ago
@SuppressWarnings
No, it would not be OK, other than in the code given, where you are returning
null instead of an actual Builder. See this code, it compiles with no warning.– Andy Turner
4 hours ago
null
Builder
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Note that it is recommended to use the existing JDK interfaces, so in your case you might use
Function<A,B>.– daniu
6 hours ago