Question

There exists interface Algorithm

There exists class MathAlgorythm implements Algorithm (returns MathResult, which implements Result)

There exists class ChemitryAlgorythm implements Algorithm (returns ChemitryResult, which implements Result)

Additionally, there exists a Context class, which is used to pass data to these Algos. Data is passed in the following manner:

public Result executeStrategy(Data data) {
    return algo.execute(data);
}

Suppose I, executeStrategy and get back
return MathAlgorithm.execute(data); I get something of type Result right?

I then execute
return ChemitryAlgorithm.execute(data); Again i get something Result

Question:
Result is an interface. I need to gain access to concrete class implementation as MathResult or ChemistryResult. In other words. Once i get something of type Result, i need to dig deeper and know what class hides behind the interface

I hope this rambling is not too confusing.

Thank you for reading and responding

Answer 1

If you give Result a method like T get() which the concrete implementations have to implement, then you don’t need to know about the concrete implementations.