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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.

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