Return Type in F-Bounded Polymorphism Java The 2019 Stack Overflow Developer Survey Results Are In Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) The Ask Question Wizard is Live! Data science time! April 2019 and salary with experienceIs Java “pass-by-reference” or “pass-by-value”?How do I efficiently iterate over each entry in a Java Map?Should we @Override an interface's method implementation?What is the difference between public, protected, package-private and private in Java?How do I read / convert an InputStream into a String in Java?When to use LinkedList over ArrayList in Java?How do I generate random integers within a specific range in Java?How do I convert a String to an int in Java?Creating a memory leak with JavaHow should I have explained the difference between an Interface and an Abstract class?
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Return Type in F-Bounded Polymorphism Java
The 2019 Stack Overflow Developer Survey Results Are In
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
The Ask Question Wizard is Live!
Data science time! April 2019 and salary with experienceIs Java “pass-by-reference” or “pass-by-value”?How do I efficiently iterate over each entry in a Java Map?Should we @Override an interface's method implementation?What is the difference between public, protected, package-private and private in Java?How do I read / convert an InputStream into a String in Java?When to use LinkedList over ArrayList in Java?How do I generate random integers within a specific range in Java?How do I convert a String to an int in Java?Creating a memory leak with JavaHow should I have explained the difference between an Interface and an Abstract class?
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I have an interface:
public interface Message<T extends Message<T>>
I have a class that implements this method as
public class FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>
And I have this method:
private <T extends Message<T>> Mono<T> getDomainModel(ConsumerRecord<String, String> record)
When I try to return an object of type Mono<FulfilmentReleaseDomModel> from this method, the compiler throws an error and asks me to cast it to (Mono<T>).
My question is, since I have bounded T to extends Message, and FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>, why do I need to cast it to Mono<T>?
java type-conversion type-erasure
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
add a comment |
I have an interface:
public interface Message<T extends Message<T>>
I have a class that implements this method as
public class FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>
And I have this method:
private <T extends Message<T>> Mono<T> getDomainModel(ConsumerRecord<String, String> record)
When I try to return an object of type Mono<FulfilmentReleaseDomModel> from this method, the compiler throws an error and asks me to cast it to (Mono<T>).
My question is, since I have bounded T to extends Message, and FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>, why do I need to cast it to Mono<T>?
java type-conversion type-erasure
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
add a comment |
I have an interface:
public interface Message<T extends Message<T>>
I have a class that implements this method as
public class FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>
And I have this method:
private <T extends Message<T>> Mono<T> getDomainModel(ConsumerRecord<String, String> record)
When I try to return an object of type Mono<FulfilmentReleaseDomModel> from this method, the compiler throws an error and asks me to cast it to (Mono<T>).
My question is, since I have bounded T to extends Message, and FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>, why do I need to cast it to Mono<T>?
java type-conversion type-erasure
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
I have an interface:
public interface Message<T extends Message<T>>
I have a class that implements this method as
public class FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>
And I have this method:
private <T extends Message<T>> Mono<T> getDomainModel(ConsumerRecord<String, String> record)
When I try to return an object of type Mono<FulfilmentReleaseDomModel> from this method, the compiler throws an error and asks me to cast it to (Mono<T>).
My question is, since I have bounded T to extends Message, and FulfilmentReleasedDomModel implements Message<FulfilmentReleasedDomModel>, why do I need to cast it to Mono<T>?
java type-conversion type-erasure
java type-conversion type-erasure
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
asked Mar 22 at 6:34
Prashant PandeyPrashant Pandey
457316
457316
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
A common misconception about generics is that the callee decides what the generic type is. No, the caller does.
You, as the writer of the method, don't get to decide what T is. By returning Mono<FulfilmentReleasedDomModel>, you are saying that T must be FulfilmentReleasedDomModel. But in actuality, the caller of your method will decide what T is. They could declare a type called Foo that implements Message<Foo> and say that T is Foo. You would need to return a Mono<Foo> instead.
It seems like your method should not be generic, because the callee is deciding what type to use:
private Mono<FulfilmentReleasedDomModel> getDomainModel(ConsumerRecord<String, String> record)
Alternatively, if you want to make this method more flexible, so that you can change its implementation to return something else without changing its return type, you can use generic wildcards:
private Mono<? extends Message> getDomainModel(ConsumerRecord<String, String> record)
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
A common misconception about generics is that the callee decides what the generic type is. No, the caller does.
You, as the writer of the method, don't get to decide what T is. By returning Mono<FulfilmentReleasedDomModel>, you are saying that T must be FulfilmentReleasedDomModel. But in actuality, the caller of your method will decide what T is. They could declare a type called Foo that implements Message<Foo> and say that T is Foo. You would need to return a Mono<Foo> instead.
It seems like your method should not be generic, because the callee is deciding what type to use:
private Mono<FulfilmentReleasedDomModel> getDomainModel(ConsumerRecord<String, String> record)
Alternatively, if you want to make this method more flexible, so that you can change its implementation to return something else without changing its return type, you can use generic wildcards:
private Mono<? extends Message> getDomainModel(ConsumerRecord<String, String> record)
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
add a comment |
A common misconception about generics is that the callee decides what the generic type is. No, the caller does.
You, as the writer of the method, don't get to decide what T is. By returning Mono<FulfilmentReleasedDomModel>, you are saying that T must be FulfilmentReleasedDomModel. But in actuality, the caller of your method will decide what T is. They could declare a type called Foo that implements Message<Foo> and say that T is Foo. You would need to return a Mono<Foo> instead.
It seems like your method should not be generic, because the callee is deciding what type to use:
private Mono<FulfilmentReleasedDomModel> getDomainModel(ConsumerRecord<String, String> record)
Alternatively, if you want to make this method more flexible, so that you can change its implementation to return something else without changing its return type, you can use generic wildcards:
private Mono<? extends Message> getDomainModel(ConsumerRecord<String, String> record)
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
add a comment |
A common misconception about generics is that the callee decides what the generic type is. No, the caller does.
You, as the writer of the method, don't get to decide what T is. By returning Mono<FulfilmentReleasedDomModel>, you are saying that T must be FulfilmentReleasedDomModel. But in actuality, the caller of your method will decide what T is. They could declare a type called Foo that implements Message<Foo> and say that T is Foo. You would need to return a Mono<Foo> instead.
It seems like your method should not be generic, because the callee is deciding what type to use:
private Mono<FulfilmentReleasedDomModel> getDomainModel(ConsumerRecord<String, String> record)
Alternatively, if you want to make this method more flexible, so that you can change its implementation to return something else without changing its return type, you can use generic wildcards:
private Mono<? extends Message> getDomainModel(ConsumerRecord<String, String> record)
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
A common misconception about generics is that the callee decides what the generic type is. No, the caller does.
You, as the writer of the method, don't get to decide what T is. By returning Mono<FulfilmentReleasedDomModel>, you are saying that T must be FulfilmentReleasedDomModel. But in actuality, the caller of your method will decide what T is. They could declare a type called Foo that implements Message<Foo> and say that T is Foo. You would need to return a Mono<Foo> instead.
It seems like your method should not be generic, because the callee is deciding what type to use:
private Mono<FulfilmentReleasedDomModel> getDomainModel(ConsumerRecord<String, String> record)
Alternatively, if you want to make this method more flexible, so that you can change its implementation to return something else without changing its return type, you can use generic wildcards:
private Mono<? extends Message> getDomainModel(ConsumerRecord<String, String> record)
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
answered Mar 22 at 6:55
SweeperSweeper
72.8k1075144
72.8k1075144
add a comment |
add a comment |
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