如何摆脱类型转换？

Question

I had a fat interface:

public interface ISolver {
    void solve();   
    String printMsgs();    
    boolean hasSolution();    
    int getLeaderId();      
    void add(Agent agent);    
    void add(int item);    
    void add(String item);    
    void addAll(Agent[] data);    
    void addAll(int[] data);    
    void addAll(String[] data);     
    public void initiateStartState();       
    Agent next();    
    boolean hasNext();      
    public List<Integer> getLeftSenders();    
    public List<Integer> getRightSenders();    
    public List<Integer> getCurrentLeaders();    
    Agent get(int idx);    
}

Two classes inherit this interface:

public class OneDirectSolver extends Solver{
    // some code..
}

public class BiDirectSolver extends Solver{
    // some code..
}

Class BiDirectSolver uses all methods declared in ISolver , but OneDirectSolver uses only few methods. I want to follow Interface Segregation Principle. So, I left in ISolver only common methods. Methods that specific for BiDirectSolver I move in another interface which extends ISolver

public interface ISolver {
    void solve();
    String printMsgs();
    boolean hasSolution();
    int getLeaderId();
    void add(Agent agent);
    void add(int item);
    void add(String item);
    void addAll(Agent[] data);
    void addAll(int[] data);
    void addAll(String[] data);
    public void initiateStartState();
    Agent next();
    boolean hasNext();
}

public interface BiDirectSolvable extends ISolver {
    public List<Integer> getLeftSenders();
    public List<Integer> getRightSenders();
    public List<Integer> getCurrentLeaders();
    Agent get(int idx);
}

But now I have another problem. I try to describe it. So, I have 2 clients of BiDirectSolver , and OneDirectSolver :

public class OneDirectPanel extends MyAbstractPanel {

    private OneDirectSolvable solver;

    public void setSolver(OneDirectSolver solver) {
        this.solver = solver;
    }
    //some code..
}

public class BiDirectPanel extends MyAbstractPanel {

    private BiDirectSolvable solver;

    public void setSolver(BiDirectSolvable solver) {
        this.solver = solver;
    }
    // some code
}

And now I want to show fragment of my main class in which I create instances of OneDirectPanel, BiDirectPanel and ISolver:

public class GUI {
    private ISolver solver;
    private MyAbstractPanel panelWithPicture;
    // a lot of code..
    if (comboBoxForMode.getSelectedItem().equals("one direct")) {
        solver = new OneDirectSolver();
        panelWithPicture = new OneDirectPanel();
        panelWithPicture.setSolver((OneDirectSolver)solver);
    } else {
        solver = new BiDirectSolver();
        panelWithPicture = new BiDirectPanel();
        panelWithPicture.setSolver((BiDirectSolvable)solver);
    }
}

I see only one solution:

if (comboBoxForMode.getSelectedItem().equals("one direct")) {
    OneDirectSolver solver = new OneDirectSolver();
    panelWithPicture = new OneDirectPanel();
    panelWithPicture.setSolver(solver);
} else {
    BiDirectSolvable solver = new BiDirectSolver();
    panelWithPicture = new BiDirectPanel();
    panelWithPicture.setSolver(solver);
}

But it is impossible to me because I must to do some actioms with solver after it was created. I must to do it in all cases. So, I do it in main class. So, in main class I must to declare reference with type ISolver.

UPD: Most of all, if I do some actions with solver in main class it must affect on solvers in OneDirectPanel and BiDirectPanel.

Answer 1

Since you temporarily need a more specific runtime type, you could assign to this.solver afterwards:

private ISolver solver;
...
if (comboBoxForMode.getSelectedItem()
                    .equals("one direct")) {
                OneDirectSolver solver = new OneDirectSolver();
                panelWithPicture = new OneDirectPanel();
                panelWithPicture.setSolver(solver);
                this.solver = solver;
            } else {
                BiDirectSolvable solver = new BiDirectSolver();
                panelWithPicture = new BiDirectPanel();
                panelWithPicture.setSolver(solver);
                this.solver = solver;
            }

Answer 2

first of all you can put your solver instance as a property of MyAbstractPanel. This way you have a base solver property.

    public abstract class MyAbstractPanel {

       private ISolver solver;

      public void setSolver(ISolver solver) {
         this.solver = solver;
      }

      public void someWork(){
         this.solver.someWork(); 
      }
     // implement this in child class
      public abstract void doSomeSpecificWork();

  }

    //assign solver object
    ISolver solver = new OneDirectSolver();

   public class BiDirectPanel extends MyAbstractPanel {
      public void doSomeSpecificWork(){
          ((OneDirectSolver)solver).doSomeSpecificWork();
     }
// some code

}

since solver is a attribute of panel i think it is not a good practice to keep a referance of ISolver type in your main class. hope this helps.