// Purpose. Template Method design pattern

// 1. Standardize the skeleton of an algorithm in a base class "template" method
// 2. Common implementations of individual steps are defined in the base class
// 3. Steps requiring peculiar implementations are "placeholders" in base class
// 4. Derived classes can override placeholder methods
// 5. Derived classes can override implemented methods
// 6. Derived classes can override and "call back to" base class methods

abstract class Generalization {
   // 1. Standardize the skeleton of an algorithm in a "template" method
   public void findSolution() {
      stepOne();
      stepTwo();
      stepThr();
      stepFor();
   }
   // 2. Common implementations of individual steps are defined in base class
   protected void stepOne() { System.out.println( "Generalization.stepOne" ); }
   // 3. Steps requiring peculiar impls are "placeholders" in the base class
   abstract protected void stepTwo();
   abstract protected void stepThr();
   protected void stepFor() { System.out.println( "Generalization.stepFor" ); }
}

abstract class Specialization extends Generalization {
   // 4. Derived classes can override placeholder methods
   // 1. Standardize the skeleton of an algorithm in a "template" method
   protected void stepThr() {
      step3_1();
      step3_2();
      step3_3();
   }
   // 2. Common implementations of individual steps are defined in base class
   protected void step3_1() { System.out.println( "Specialization.step3_1" ); }
   // 3. Steps requiring peculiar impls are "placeholders" in the base class
   abstract protected void step3_2();
   protected void step3_3() { System.out.println( "Specialization.step3_3" ); }
}

class Realization extends Specialization {
   // 4. Derived classes can override placeholder methods
   protected void stepTwo() { System.out.println( "Realization   .stepTwo" ); }
   protected void step3_2() { System.out.println( "Realization   .step3_2" ); }
   // 5. Derived classes can override implemented methods
   // 6. Derived classes can override and "call back to" base class methods
   protected void stepFor() {
      System.out.println( "Realization   .stepFor" );
      super.stepFor();
}  }

class TemplateMethodDemo {
   public static void main( String[] args ) {
      Generalization algorithm = new Realization();
      algorithm.findSolution();
}  }

// Generalization.stepOne
// Realization   .stepTwo
// Specialization.step3_1
// Realization   .step3_2
// Specialization.step3_3
// Realization   .stepFor
// Generalization.stepFor