factory-method

CodingService.java

public abstract class CodingService {
  abstract Developer createDeveloper();
  public void writeCode() {
    Developer dev = createDeveloper();
    String code = dev.writeCode();
    System.out.println(code);
  }
}

Developer.java

public interface Developer {
  String writeCode();
}

JavaCodingService.java

public class JavaCodingService extends CodingService {
  @Override
  Developer createDeveloper() {
    return new JavaDeveloper();
  }
}

JavaDeveloper.java

public class JavaDeveloper implements Developer {
  @Override
  public String writeCode() {
    return "-- some java code --";
  }
}

PhpCodingService.java

public class PhpCodingService extends CodingService {
  @Override
  Developer createDeveloper() {
    return new PhpDeveloper();
  }
}

PhpDeveloper.java

public class PhpDeveloper implements Developer {
  @Override
  public String writeCode() {
    return "-- some php code --";
  } 
}

Program.java

public class Program {
  public static void main(String[] args) {
    writeJavaCode();
    writePhpCode();
  }
  
  public static void writeJavaCode() {
    CodingService codingService = new JavaCodingService();
    codingService.writeCode();
  }
  
  public static void writePhpCode() {
    CodingService codingService = new PhpCodingService();
    codingService.writeCode();
  }
}