Java. Howto change methods signature

Question

Is it possible to change a methods signature in Java depending on the parameter?

Example:

Given a class, with a generic parameter MyItem<T>. Assume this class has a method, which returns T Given a second class 'myReturner()' which contains method myreturn(MyItem<T>).

Question:

Can i make myreturn(MyItem<T>) return a T object, depending on the generic parameter of MyItem?

I suppose it is not possible, because the signature is set during compile time in Java, and T is not known at compile time. If so, what is the best way to simulate a method, which will return different objects, depending on parameter? Is writing an own method for each parameter type the only way?

As to why it is possible: when compiling Java simply outputs `Object myreturn(MyItem)` as a method, removing any generic information. This method obviously can accept any object. — Viruzzo, Dec 02 '11 at 14:36
As far as I can guess Viruzzo's link should be somewhere at this link instead: docs.oracle.com/javase/tutorial/java/generics/methods.html — Crowie, May 04 '14 at 15:34

score 7 · Accepted Answer · answered Dec 02 '11 at 14:32

7

Something like this?

private <T> T getService(Class<T> type) {
    T service = ServiceTracker.retrieveService(type);
    return service;
}

answered Dec 02 '11 at 14:32

rodrigoap

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score 3 · Answer 2 · answered Dec 02 '11 at 14:32

3

Do you mean something like this:

<T> T myMethod(MyItem<T> item)

?

answered Dec 02 '11 at 14:32

Puce

37,247
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score 0 · Answer 3 · answered Dec 02 '11 at 14:32

0

You can, if you also make the whole class generic to that same type T, something like:

import java.util.ArrayList;

public class MyReturn<T> {

    public T myReturn(ArrayList<T> list){
        return null; //Your code here
    }
}

answered Dec 02 '11 at 14:32

Miquel

15,405
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score 0 · Answer 4 · edited May 23 '17 at 12:20

0

A generic return type is perfectly well possible. Look for instance here: How do I make the method return type generic? or here: Java Generics: Generic type defined as return type only

edited May 23 '17 at 12:20

Community

1
1

answered Dec 02 '11 at 14:36

Pieter

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score 0 · Answer 5 · answered Dec 02 '11 at 14:40

0

I think you want something like this:

public static void main(String[] args) {
    String bla = myMethod(new MyItem<String>());
}

public static <T> T myMethod(MyItem<T> item) {
    return null;
}

public class MyItem<T> {
    //just a dummy
}

answered Dec 02 '11 at 14:40

Fabian Barney

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Java. Howto change methods signature

5 Answers5