Design Patterns in Java (Creational) - Template Pattern

Template Pattern

• Code reuse
• Common in libraries
• Algorithm emphizes

Main

public static void main(String[] args) {

CreditCard amex = new CreditCard(new AmexStrategy());

amex.setNumber("379185883464283");

amex.setDate("04/2020");

amex.setCvv("123");

System.out.println("Amex valid? : " + amex.isValid());

CreditCard masterCard = new CreditCard(new MasterStrategy());

masterCard.setNumber("379185883464289");

masterCard.setDate("04/2020");

masterCard.setCvv("123");

System.out.println("Master valid? : " + masterCard.isValid());

}

CreditCard

public class CreditCard {

private String number;

private String date;

private String cvv;

private ValidationStrategy vs;

public CreditCard(ValidationStrategy vs){

this.vs = vs;

}

public boolean isValid(){

return vs.isValid(this);

}

}

AmexStrategy

public class AmexStrategy extends ValidationStrategy {

@Override

public boolean isValid(CreditCard c) {

boolean isValid = true;

isValid = c.getNumber().startsWith("37") || c.getNumber().startsWith("34");

isValid =  passesLuhn(c.getNumber());

return isValid;

}

}

MasterStrategy

public class MasterStrategy extends ValidationStrategy {

@Override

public boolean isValid(CreditCard c) {

boolean isValid = true;

isValid = c.getNumber().startsWith("50") ;

isValid =  passesLuhn(c.getNumber());

return isValid;

}

}