Standardize the skeleton of an algorithm in a base class "template" method
Common implementations of individual steps are defined in the base class
Steps requiring peculiar implementations are "placeholders" in base class
Derived classes can override placeholder methods
Derived classes can override implemented methods
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 void findSolution() { stepOne(); stepTwo(); stepThr(); stepFor(); } // 2. Common implementations of individual steps are defined in base class private void stepOne() { System.out.println("Generalization.stepOne"); } // 3. Steps requiring peculiar implementations are "placeholders" in the base class abstract void stepTwo(); abstract void stepThr(); 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 private void step3_1() { System.out.println("Specialization.step3_1"); } // 3. Steps requiring peculiar implementations are "placeholders" in the base class abstract protected void step3_2(); private 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(); } } public class TemplateMethodDemo { public static void main(String[] args) { Generalization algorithm = new Realization(); algorithm.findSolution(); } }
