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Thinking out code

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The simple and satisfiying art of executing a java file from the command line.

#javaseries #handmade #java #noides

Having the next java source

public class Salad { public static void main(String[] args) { System.out.println("I'm the best salad in this neighberhood!"); } }
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Run the command below, inside the folder source with java command:

java Salad.java #it prints I'm the best salad in this neighberhood!
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Now let’s create another Java file in the same folder.

public class Watermelon { public void talk() { System.out.println("I'm the best fruit!"); } }
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and call its method talk in Salad class contained in Salad file.

public class Salad { public static Watermelon watermelon = new Watermelon(); public static void main(String[] args) { watermelon.talk();//here System.out.println("I'm the best salad in this neighberhood!"); } }
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Let’s run the previous command once again.

java Salad.java #it prints Salad.java:3: error: cannot find symbol public static Watermelon watermelon = new Watermelon(); ^ symbol: class Watermelon location: class Salad .\Salad.java:3: error: cannot find symbol public static Watermelon watermelon = new Watermelon(); ^ symbol: class Watermelon location: class Salad 2 errors error: compilation failed
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Because our Salad class doesn’t know any about the Watermelon class, thought the Watermelon class contained inside the Watermelon file knows how to talk, so let’s add some watermelon to our salad.

At first, is neccesary to process our Watermelon file  into our processedFruits folder with the javac command and -d option to indicate folder location name.

javac -d processedFruits Watermelon.java
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And finally, let’s add our processedFruits folder to the original run command adding the -cp option to indicate where are compiled our java source of Watermelon file.

java -cp "processedFruits\" Salad.java #it prints I'm the best fruit! I'm the best salad in this neighberhood!
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That’s it, simple but effective:

  • Run a standalone java file.
  • Run a standalone java file adding compiled sources as need it.

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).

Tech stack

  • Java 11.
  • Windows 10.

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