This is an example of the command pattern for the ISTE 422 Final Project at RIT.

CommandPattern.java

public interface InputParser {
    // variables
    Database database;

    // methods
    void parseFile(File inputFile);

    Database getDatabase();
}


public class XmlInputParser implements InputParser {
    Database database;

    public void parseFile(File inputFile) {
        // parses the file into a database
    }

    public Database getDatabase() {
        return this.database;
    }

    // this is where you would put the private methods to parse the individual xml file
}

public class EdgeInputParser implements InputParser {
    Database database;

    public void parseFile(File inputFile) {
        // parses the file into a database
    }

    public Database getDatabase() {
        return this.database;
    }

    // this is where you would put the private methods to parse the individual edge file
}

public class RunDDLCreator {
    public static void main(string[] args)
    {
        InputParser parser;
        File inputFile;

        // this is where the
        // code to get the input file
        // would go, and then put it
        // in the inputFile variable

        switch (inputFile.fileType)
        {
            case "xml":
                Parser = new XmlInputParser();
                break;
            case "edg":
                Parser = new EdgeInputParser();
                break;
            default:
                throw new UnexpectedFiletypeException();
                break;
        }

        parser.parseFile();


        // then essentially you would do something similar to get the
        // DDL creator you need to use instantiated

        ddlcreator.createDDL();
    }
}