How to implement strategy pattern using a strategy that have another one inside?

Question

Im implementing a strategy pattern and in a specific situation, one strategy must use another strategy implementation as part of it.

For Example:

interface ProcessStrategy{

    void process();

}

public class ProcessOnFile implements ProcessStrategy{

    void process(){


    }
}

public class ProcessOnFileNetwork implements ProcessStrategy{

    void process(){


    }
}

In this case, processOnFileNetwork will encapsulate the logic inside ProcessOnFile plus some especific logic..

How can i add this functionality without repeat the code??

Thanks !

Answer 1

You could use abstract class concept.

public abstract class ProcessStrategy{
    public void process(){
        // Common code goes here
    }

}

public class ProcessOnFile extends ProcessStrategy{

    public void process(){
        super();
        // Class specific code goes here
    }
}

public class ProcessOnFileNetwork extends ProcessStrategy{

    public void process(){
        super();
        // Class specific code goes here
    }
}

Note abstract classes can have data variables too which can be utilized.