Question

Imagine the following code, written in C#:

public class Provider<T>
{
   T GetValue();  // implementation skipped for brevity
}

//

public class Converter<T1, T2>
{
    T2 Convert(T1 value);// implementation skipped for brevity
}

//

public class SomeClass // No Generics Here
{

    public T2 DoSomething<T1, T2>()
    {
        T1 value = new Provider<T1>().GetValue();
        T2 result = new Converter<T1, T2>().Convert(value);

        return result;
    }
}

// and the usage
...
SomeClass some = new SomeClass();
SomeOtherType result = some.DoSomething<SomeType, SomeOtherType>();

Is it possible to achieve the same with Java – I want to know how to call a method in Java by providing the type arguments in the method usage, like above. I’ve done this in .NET and I know Java supports type constraints and inference, I am just messing it up with the syntax.

Answer 1

Both Provider and Converter are fine as they are, your DoSomething method should be re-written like so:

public <T1, T2> T2 doSomething() {
  T1 value = new Provider<T1>().GetValue();
  T2 result = new Converter<T1, T2>().Convert(value);
  return result;
}

Which is useable like so:

SomeClass instance = new SomeClass();
Integer something = instance.<String, Integer>doSomething();