JAR file

[Abhi vijay]

Source: Devaka Cooray's Exam Simulator.

  Structure of Pack.jar
---------------------------

  (Pack.jar)
      |
      |-----Info
      |
      |----Info.java
      |
      |----InsideJar
              |
              |--Info.class

=========================================



Source code for Info.java
--------------------------------
     
     package InsideJar;
     public class Info{
          public String access(){
               return "Success";
          }
     }



=========================================



Source code for A.java
------------------------------

public class A{
     public static void main(String args[]){
          System.out.println(new InsideJar.Info().access());
     }
}


/(root)
  Pack.jar
  A.java  

Here the question is In order to compile A.java, what should be the class path?

This line states that System.out.println(new InsideJar.Info().access()); class A needs Info.class which is inside InsideJar.

So the classpath should be java -cp .: Pack.InsideJar A

But here the answer is java -cp .: Pack.jar A.

[Punit Singh]

So the classpath should be java -cp .: Pack.InsideJar A

Which type of classpath is this?
You have to give jar file name in your classpath, that is Pack.jar only, so given answer is correct, class A will find all needed classes from Pack.jar. No need to name dependent files explicitly.

[Abhi vijay]

 /(root)current directory
      classes
             source
                    B.java   A.java
                    
                      dir
                         B.class


  

Now If I have to compile A.java which uses methods and variables in B.class, then what should be my classpath?


javac -cp classes/source classes/source/A.java

This is the correct answer. But dont we have to specify dir where B.class is located?

javac -cp classes/source/dir classes/source/A.java

[James Tharakan]

javac -cp classes/source/dir classes/source/A.java
this is correct

[Punit Singh]

what is dir here?
It is just a directory or package of class B, answer will depend on this fact.

[Abhi vijay]

 (Root)/classes/source/A.java
-------------------------------------

     import dirc.B;
     public class A{
          public static void main(String args[]){
               new B();
          }
     }



================================================



(Root)/classes/source/B.java
-------------------------------------

     package dirc;
     public class B{
          public B(){
               System.out.println("Success");
          }
     }   

Source: Devaka Cooray's Simulator.

[Punit Singh]

Then you donot need to add dirc in classpath, only specify address of the directory that contains dirc folder.

  # /(root)current directory  
#       classes  
#              source  
#                     B.java   A.java  
#                       
#                       dirc  
#                          B.class  
#     

here dirc is in /classes/source, so you need to give:

javac -cp classes/source classes/source/A.java

And another clue for you that see the code of A.java:

  # import dirc.B;  //see this is searching of dirc.B, 
//so you need to give address of the parent folder of dirc
#      public class A{  
#           public static void main(String args[]){  
#                new B();  
#           }  
#      }    

[Abhi vijay]

What if the code of A.java did not have the import statement???

[Punit Singh]

Abhi vijay wrote:What if the code of A.java did not have the import statement???

Than it will try to find class B in your classpath and will not compile, as there is no such class, as it is actually dirc.B.

[Abhi vijay]

That means A.java knows where B.class resides as it says import dirc.B, so the only the path leading to dirc needs to be specified in the classpath, Am I right, Punit???

[Punit Singh]

Abhi vijay wrote:That means A.java knows where B.class resides as it says import dirc.B, so the only the path leading to dirc needs to be specified in the classpath, Am I right, Punit???

Yes you are right Abhi. Abhi what are you doing, are you making practicals and coming to conclusion or just memorizing what we say to you. If you memorizing than you will forget many things in 1-2 weeks. You should write every practical, you find in your mock exams.

[Abhi vijay]

No, Punit, I am not memorizing. I generally try out all the problems given in Mocks, in textpad. But didnt try out the above example, as I thought I should be able to answer it without trying it out. Stupid naa!!!

[Punit Singh]

Abhi vijay wrote:No, Punit, I am not memorizing. I generally try out all the problems given in Mocks, in textpad. But didnt try out the above example, as I thought I should be able to answer it without trying it out. Stupid naa!!!

I am saying you, these type of questions are most confusing questions, you must have seen those post where I, Ruben and Sachine went very long in solving a confusion and that question was raised by you, from that question Ruben has opened a new thread for again classpath confusion. Again you came back with classpath question, so come on read all recent threads of classpath and run all programs, what is going in your mind, we are running your program and you are not running your program yourself.

See your doubt here
Another doubt related to your question only

[Abhi vijay]

Ok.Punit. Will never repeat.

[Punit Singh]

Abhi vijay wrote:Ok.Punit. Will never repeat.

I am not saying to not repeat, I just want to say you make all practicals and be clear on every concept, if you do not run these programs, then you are missing an important part of your java.

If you feel boring programs on notepad, then use editor, like eclipse, netbeans, but run command line programs from command lines only. Or you can run all your program from command line, just for writing purpose use editor, as it will save your time.

[Abhi vijay]

Punit, what i meant when i said I wont repeat is that I will always try out the program .

[Punit Singh]

Abhi vijay wrote:Punit, what i meant when i said I wont repeat is that I will always try out the program .

For my case I never used notepad, my all programs are written using Eclipse, and run through eclipse only, I ran only few programs that were requiring command line from the command line. It's your personnel choice.