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Creating a java library, a place where any problem can be resolved.

#java #develop #jvm #jar

Starting with the next class, called SummerDelivery, a delivery service planned to refresh a hot summer day...

public class SummerDelivery {

    public static void main(String[] args) {
        for (String order: args) {
            switch(order) {
                case "PEACH_TENTATION":
                    System.out.println("Peach Tentation Order...");
                    //Anyone knows how to prepared it?
                    break;
                case "FROZEN_APPLE":
                    System.out.println("Frozen Apple Order...");
                    //Anyone knows how to prepared it?
                    break;
                default:
                    System.out.println("Unexpected Order...");
                    break;
            }
        }   
    }
}
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But if we running the command to order a PEACH_TENTATION or a FROZEN_APPLE:

➜ java .\SummerDelivery.java PEACH_TENTATION FROZEN_APPLE
#it prints
Peach Tentation Order...
Frozen Apple Order...
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The program doesn’t know how to prepare one of its offered beverages, it needs a source with beverages preparation knowledge.

So, having the source below, capable of resolving SummerDelivered needs, called TropicalJuice:

public class TropicalJuice {

    class Storage {
        public static final String PEACH_JUICE = "Peach juice";
        public static final String APPLE_JUICE = "Apple juice";
        public static final String LIMON_JUICE = "Limon juice";     
    }

    class Fridge {
        public static final String ICE_CUBES = "Ice cubes";
        public static final String CHERRY = "Cherry";
        public static final String LIMON_SHOT = "Limon shot";       
    }

    public class JuiceMan {
        public void preparePeachTentation() {
            System.out.println(String.format("Mixing a 250ml of %s with a %s and a few crushed %s.", 
                Storage.PEACH_JUICE, Fridge.LIMON_SHOT, Fridge.ICE_CUBES));
        }

        public void prepareFrozzenApple() {
            System.out.println(String.format("Mixing a 250ml of %s with 2 parts of crushed %s adding 100ml of %s.", 
                Storage.APPLE_JUICE, Fridge.ICE_CUBES, Storage.LIMON_JUICE));
        }
    }
}
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It's necessary to include it inside SummerDelivery class to attend juice orders.

First of all, we compile TropicalJuice to a class file, executing the command below:

➜ javac -d . .\TropicalJuice.java
#it generates TropicalJuice.class,TropicalJuice$Fridge.class,TropicalJuice$JuiceMan.class,TropicalJuice$Storage.class
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After, we package their .class files generated in a storage called tropical.jar, our java library, running the command below:

➜ jar --create --file tropical.jar .\TropicalJuice.class '.\TropicalJuice$Fridge.class' '.\TropicalJuice$JuiceMan.class' '.\TropicalJuice$Storage.class'
#it generates a jar called tropical.jar
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With the created tropical.jar, we add to SummerDeliver class the library new methods.

public class SummerDelivery {
    private static TropicalJuice tropicalJuice = new TropicalJuice();
    private static TropicalJuice.JuiceMan juiceMan = tropicalJuice.new JuiceMan();

    public static void main(String[] args) {
        for (String order: args) {
            switch(order) {
                case "PEACH_TENTATION":
                    System.out.println("Peach Tentation Order...");
                    juiceMan.preparePeachTentation();
                    break;
                case "FROZZEN_APPLE":
                    System.out.println("Frozen Apple Order...");
                    juiceMan.prepareFrozzenApple();
                    break;
                default:
                    System.out.println("Unexpected Order...");
                    break;
            }
        }   
    }
}
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Adding the library in the first executed command:

➜ java -cp .\tropical.jar .\SummerDelivery.java FROZZEN_APPLE PEACH_TENTATION WATER
#it prints
Frozen Apple Order...
Mixing a 250ml of Apple juice with 2 parts of crushed Ice cubes adding 100ml of Limon juice.
Peach Tentation Order...
Mixing a 250ml of Peach juice with a Limon shot and a few crushed Ice cubes.
Unexpected Order...
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Yep! Now SummerDelivery knows how to refresh this summer! But it still doesn’t know how to serve a Water glass. If you know how to resolve it, please feel free to add it and test it to practice.

That’s all!

  1. A problem happened.
  2. We create a solution to solve it.
  3. Package the solution as a library.
  4. Add it and test it.
  5. Problem fixed.

Command and options dictionary:

  • java run .class and .java files.
  • javaccompile .java files and creates .class files.
  • -dindicate output folder.
  • -cpindicate compiled folders directory(classpath).
  • jar to execute actions related to java libraries.
  • —create indicate jar action command.
  • —file indicates a name file.

Tech Stack:

  • Java 11.
  • Windows 10.

Repo:

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