How one can implement Technique Design Sample in Java? (with Actual World Instance, Professionals and Cons)

Technique Design sample is one among most helpful versatile sample, you’ll typically see utilized in Object Oriented design. This sample is likely one of the behavioral sample talked about by well-known Gang of 4 in there design sample classics Parts of Reusable Design Sample is Software program growth. As per definition goes, Technique sample permits you to encapsulate a set of algorithms and make them interchangeable. One of the best factor about Technique sample is that it permits you to cross a dynamic code to a way very like Lambda expression. The truth is, it was one of many strategy to obtain similar impact previous to Java 8. Additionally, there are a number of instance of Technique Sample in JDK itself like Comparator and Comparable are the perfect instance of Technique Sample in Java. 

Through the use of Technique design sample, we will remedy this upkeep downside and make this code Open for extension and Closed for modification. We’ll introduce a PostageCalculationStrategy to calculate postage for various sorts of supply medium.

import org.apache.log4j.Logger;

/**
  * Java program to implement Technique design sample. This design violets
  * Open closed design precept, and never closed for modification. Through the use of
  * Technique sample, we are going to repair this hole.

  * @writer Javin
  */
public class StrategyPatternDemo {

    non-public static closing Logger logger = Logger.getLogger(Take a look at.class);

    public static void important(String args[]) {
        Merchandise present = new Merchandise(100);
        int postalCharge = PostageCalculator.postage(present, DeliveryType.REGISTERED);

        System.out.printf("Weight : %dg, Supply Sort : %s, 
Postal Expenses : %dc %n",
                present.getWeight(), DeliveryType.REGISTERED, postalCharge );
     
        postalCharge = PostageCalculator.postage(present, DeliveryType.SPEEDPOST);
     
        System.out.printf("Weight : %dg, Supply Sort : %s,
 Postal Expenses : %dc %n",
                present.getWeight(), DeliveryType.SPEEDPOST, postalCharge );
    }
}

enum DeliveryType {
    SPEEDPOST, REGISTERED, SURFACE_MAIL;
}

class Merchandise {
    non-public int weight;  //in grams

    public Merchandise(int weight) {
        this.weight = weight;
    }

    public int getWeight() {
        return weight;
    }
}

class PostageCalculator {

    public static int postage(Merchandise merchandise, DeliveryType deliveryType) {    
        int postage = 0;

        change (deliveryType) {
            case SURFACE_MAIL:
                postage = merchandise.getWeight()  1; //1 cent per gram
                break;
            case REGISTERED:
                postage = merchandise.getWeight()  5; //5 cent per gram
                break;
            case SPEEDPOST:
                postage = merchandise.getWeight()  8; //8 cent per gram
                break;
            default:
                throw new IllegalArgumentException("Invalid Supply kind");
        }

        return postage;
    }
}

Output
Weight : 100g, Supply Sort : REGISTERED, Postal Expenses : 500c
Weight : 100g, Supply Sort : SPEEDPOST, Postal Expenses : 800c

import org.apache.log4j.Logger;

/**
  * Java program to implement Technique design sample. This design voilates
  * Open closed design precept, and never closed for modification. Through the use of
  * Technique sample, we are going to repair this hole.
  *
  * @writer
  */
public class StrategyTest {

    non-public static closing Logger logger = Logger.getLogger(StrategyTest.class);

    public static void important(String args[]) {
        Merchandise present = new Merchandise(100);
        PostageCalculator postCalc = new PostageCalculator(new SurfaceMail());
     
        int postalCharge = postCalc.postage(present);

        System.out.printf("Weight : %dg, Supply Sort : %s, 
Postal Expenses : %dc %n",
                present.getWeight(), postCalc.getDeliveryType(), postalCharge );
     
        postCalc.setDeliveryType(new SpeedPost());
        postalCharge = postCalc.postage(present);
     
        System.out.printf("Weight : %dg, Supply Sort : %s, 
Postal Expenses : %dc %n",
                present.getWeight(), postCalc.getDeliveryType(), postalCharge );
    }
}

class Merchandise {
    non-public int weight;  //in grams

    public Merchandise(int weight) {
        this.weight = weight;
    }

    public int getWeight() {
        return weight;
    }
}

class PostageCalculator {
    non-public DeliveryType deliveryType;

    public DeliveryType getDeliveryType() {
        return deliveryType;
    }

    public void setDeliveryType(DeliveryType deliveryType) {
        this.deliveryType = deliveryType;
    }
 
    public PostageCalculator(DeliveryType medium){
        this.deliveryType = medium;
    }
 

    public int postage(Merchandise merchandise) {    
        return merchandise.getWeight()deliveryType.price();

    }
}

interface DeliveryType{
    public int price();
}

class SurfaceMail implements DeliveryType{

    @Override
    public int price() {
        return 1;
    }

}

class RegisteredMail implements DeliveryType{

    @Override
    public int price() {
       return 5;
    }
 
}

class SpeedPost implements DeliveryType{

    @Override
    public int price() {
        return 8;
    }

}

1) One of many important benefit of Technique Sample is that it makes your software program Open for Extension however Closed for modification by making use of Open closed design precept. This implies, your tried and examined code stays unchanged, whenever you add new functionalities to your software program.

3) Technique Sample additionally promotes Single Accountability Principle. Shopper class, which calculates postal cost is now unbiased of price related to completely different supply varieties. Later for those who resolve to provided any low cost on a selected supply kind, or a price of a supply kind modifications. 

4) Use of Technique Sample additionally makes testing simple. Since Shopper Code, which makes use of Methods are solely depending on a Technique interface and never on any specific implementation, you’ll be able to take a look at code inside Shopper, even when your technique or algorithm is just not prepared. 

5) Technique Sample vastly simplify consumer code, consumer like Sorting methodology can delegate comparability of object to Comparator in a single line. Like in our instance calculating price of various supply modicum is delegated.

7) One other good thing about this sample which comes from use of Open closed design precept is extensibility, you might be free to implement as many algorithm or technique as you want. This extensibility is de facto large, simply think about what number of instances Comparator has been carried out for various kinds of object.

Additionally, right here is  UML diagram of Technique design sample to know the intent and construction of Technique Design Sample in Java:

1. Technique Sample permits a Shopper to make use of completely different algorithm, primarily based upon various kinds of calculation. For instance a SalaryCalcuator can use completely different technique to calculate wage primarily based upon kind of worker. E.g. utilizing hourly price for Hourly worker, day by day price for day by day worker and stuck month-to-month wage together with allowance for full time workers.

4. Among the finest instance of Technique sample in JDK is Comparator interface, which defines an technique to check object. Since completely different object is in contrast in another way, Shopper which makes use of Comparator e.g. Collections.type(), which makes use of Comparator for sorting goal, is offered proper Technique at runtime. Benefit of that is that, code to type the gathering  is unbiased of kind of object and the way they evaluate. All it must know that, they implement Comparator and has evaluate() methodology.

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