Thread: Java How to design - Interface Usage?

I have a class as shown below.

This class has a method addFilter with 2 parameters (type String and type Command1 )
public class Command1 {
public StringBuffer addFilter(String query, Command1 dataBase) {

//concrete implementation

return query;

}
}

I have another class Command2. Here I need a similar method. The only difference is in the type of parameters passed. (type String and type Command).

public class Command2 {
//TO DO:
public StringBuffer addFilter(String query, Command2 cmd) {

//concrete implementation

return query;

}
}

I have started by using Interface
public interface Helper {

public StringBuffer addFilter(String query, XXXXX parameter2);

}

I would like the classes Command1 and Command2 to implement the interface Helper and override it these two public classes.
However my problem is in dealing with the 2nd parameter. Am I right in my approach? Can anybody tell me how do I handle this issue?

public class Command1 implements Helper{

//I need to pass the 2nd paramter as type Command1
@Override
public StringBuffer addFilter(String query, Command1 dataBase) {

//concrete implementation

return query;

}
}

public class Command2 {
//TO DO:
//I need to pass the 2nd paramter as type Command2
@Override
public StringBuffer addFilter(String query, Command2 cmd) {

//concrete implementation

return query;

}
}

public interface Helper {

//What should the type of XXXXX be??
public StringBuffer addFilter(String query, XXXXX parameter2);

}

--- Update ---

public class Command1 implements Helper{

//need to pass the 2nd paramter as type Command1 ??
@Override
public StringBuffer addFilter(String query, Command1 dataBase) {

//concrete implementation

return query;

}
}

public class Command2 implements Helper{
//TO DO:
//need to pass the 2nd paramter as type Command2

@Override
public StringBuffer addFilter(String query, Command2 cmd) {

//concrete implementation

return query;

}
}

public interface Helper {

//What should the type of XXXXX be??
public StringBuffer addFilter(String query, XXXXX parameter2);

}