Design Patterns - Factory Method

Design Patterns | Factory Method

References
Example

References
- Definition: (source: http://en.wikipedia.org/wiki/Factory_method_pattern)
  
  Define an interface for creating an object, but let subclasses decide which class to instantiate.
  The Factory method lets a class defer instantiation it uses to subclasses.

Example

The Product:

public interface Report {
    public String generate(final String data);
}

The Concrete Product:

public class ReportHtml implements Report {
    public String generate(final String csvData) {
        final StringBuilder htmlData = new StringBuilder();

        if (csvData != null) {
            final String[] dataElements = csvData.split(",");

            for (final String dataElement : dataElements) {
                htmlData.append(String.format("<b>%s</b>", dataElement));
            }
        }

        return htmlData.toString();
    }
}

The Factory:

public class ReportFactory {
    public static Report getReport(final String type) {
        if ("html".equalsIgnoreCase(type)) {
            return new ReportHtml();
        }

        return null;
    }
}

A simple class to test the Factory Method design pattern:

public class FactoryMethodPatternTest {
    public static void main(String[] args) {
        // create the report
        final Report report = ReportFactory.getReport("html");

        // call methods
        final String htmlReport = report.generate("1,abc");

        System.out.println(htmlReport);
    }
}