How to compile java package structures using javac

Question

I am trying to compile (from the command line) a java package that imports another package of my own. I was following a tutorial online but it seems that I get an error when I try to compile the final java file (CallPackage.java).

Here is the file structure:

+ test_directory (contains CallPackage.java)    -> importpackage        -> subpackage (contains HelloWorld.java) 

Here is CallPackage.java:

/// CallPackage.java import importpackage.subpackage.*; class CallPackage{   public static void main(String[] args){   HelloWorld h2=new HelloWorld();   h2.show();   } } 

and here is HelloWorld.java:

///HelloWorld.java  package importpackage.subpackage;  public class HelloWorld {   public void show(){   System.out.println("This is the function of the class HelloWorld!!");   } } 

Attempted Steps

1. Go to the subpackage and compile HelloWorld.java with $javac HelloWorld.java.
2. Go to test_directory and compile CallPackage.java with $javac CallPackage.java.

This gives me an error on the last command:

CallPackage.java:1: package importpackage.subpackage does not exist import importpackage.subpackage.*; ^ CallPackage.java:4: cannot find symbol symbol  : class HelloWorld location: class CallPackage   HelloWorld h2=new HelloWorld();   ^ CallPackage.java:4: cannot find symbol symbol  : class HelloWorld location: class CallPackage   HelloWorld h2=new HelloWorld();                     ^ 3 errors 

How can I compile both packages? Thanks so much for any help!

Answer 1

The issue was that the class path needs to be set for each command (javac and java):

Attempted Steps

1. instead of going to subpackage, compile HelloWorld.java from the top_level:

   $javac -cp . importpackage/subpackage/HelloWorld.java

2. compile CallPackage.java in the same way:

   $javac -cp . CallPackage.java

3. run the file using the class path also:

   $java -cp . CallPackage

NOTE: running "$java CallPackage" will give an error "Error: Could not find or load main class CallPackage"

In summary, during each step, the class path must be specified. It worked after running it as such.

Answer 2

Same situation to me. And I came to take over it by compiling classes at the same time.
For example, here is my project:

+ beerV1    -> classes    -> src          -> com               -> example                    -> model                         -> BeerExpert.java                    -> web                         -> BeerSelect.java 

BeerExpert.java:

package com.example.model; import ...  public class BeerExpert{     ... } 

BeerSelect.java:

package com.example.web; import com.example.model.*; import ...  public class BeerSelect {       ... } 

As you can see: BeerSelect.java is trying to import classes in com.example.model package.
At the first time, I compiled BeerExert.java first by command:

--> javac -d classes src/com/example/model/BeerExpert.java

Then:
--> javac -d classes src/com/example/web/BeerSelect.java

And the result was:
-->... error: package com.example.model does not exist

So, I knew that compiling multiple classes separately will not work in this case.

After suffering on google, I found this very simple way to solve the problem:
Just compile all at once:

--> javac -d classes src/com/example/model/BeerExpert.java src/com/example/web/BeerSelect.java  

Finally, here is what I got:

 + beerV1            -> classes                  -> com                       -> example                            -> model                                 -> BeerExpert.class                            -> web                                 -> BeerSelect.class            -> src                  -> com                       -> example                            -> model                                 -> BeerExpert.java                            -> web                                 -> BeerSelect.java 

Hope that helps.