Monday, 21 September 2015

Template Method Pattern

Template method defines the steps to execute an algorithm and it can provide default implementation that might be common for all or some of the subclasses.

package oops.design.patterns.template;
public abstract class InterviewProcess {

       abstract void written();
       abstract void technical();
       abstract void manager();
       abstract void hrRounds();

       // Template method - Sequence of processes.
       public final void judgeCandidate() {
              written();
              technical();
              manager();
              hrRounds();
       }
}

package oops.design.patterns.template;
public class OrangeInterview extends InterviewProcess {

       @Override
       void written() {
              System.out.println("written : Orange!");
       }

       @Override
       void technical() {
              System.out.println("technical : Orange!");
       }

       @Override
       void manager() {
              System.out.println("manager : Orange!");
       }

       @Override
       void hrRounds() {
              System.out.println("hr rounds : Orange!");
       }
}

package oops.design.patterns.template;
public class ExpediaInterview extends InterviewProcess {

       @Override
       void written() {
              System.out.println("written : Expedia!");
       }

       @Override
       void technical() {
              System.out.println("technical : Expedia!");
       }

       @Override
       void manager() {
              System.out.println("manager : Expedia!");
       }

       @Override
       void hrRounds() {
              System.out.println("hr rounds : Expedia!");
       }
}

package oops.design.patterns.template;
public class TestCandidate {
       public static void main(String[] args) {
              InterviewProcess orangeInterview = new OrangeInterview();
              orangeInterview.judgeCandidate();
             
              System.out.println("\n");
             
              InterviewProcess expediaInterview = new ExpediaInterview();
              expediaInterview.judgeCandidate();
       }
}
Output:
written : Orange!
technical : Orange!
manager : Orange!
hr rounds : Orange!

written : Expedia!
technical : Expedia!
manager : Expedia!
hr rounds : Expedia!

                                         
Template Method Pattern in JDK

1.All non-abstract methods of java.io.InputStream, java.io.OutputStream, java.io.Reader and java.io.Writer.

2.All non-abstract methods of java.util.AbstractList, java.util.AbstractSet and java.util.AbstractMap.

Things to remember
1.Template method should be final.

2.Template method should consist of certain steps whose order is fixed and for some of the methods; implementation differs from base class to subclass.

3.Most of the times, subclasses calls methods from super class however in template pattern, superclass template method calls methods from subclasses.

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