how to compile and run two different java programs with instances of one in another which are in different directories?

Question

my first java program is

import java.io.*;
class pgm10a
{
    public static void main(String args[])
    {
        pgm10b b=new pgm10b();
        b.display();
    }
    void display()
    {
        System.out.println("A class");
    }
}

it is saved in C:\NNK\pack1 the second program is

import java.io.*;
class pgm10b
{
    void pgm10b()
    {
        pgm10a a=new pgm10a();
        a.display();
    }
    void display()
    {
        System.out.println("Class B");
    }
}

it is in C:\NNK\pack2 I want to run pgm10a but it keeps showing pgm10b not found exception. i have set the class path and compiled for both and both are compiled successfully. but when i try to run them it shows pgm10b not found.

@JonnyHenly i don't understand...include as in import the class. can you give a example — Nn Karthik
– Nn Karthik, Commented Jul 15, 2016 at 2:58
If they're in the same package they shouldn't be in different directories. — user207421
– user207421, Commented Jul 15, 2016 at 3:37
Then you haven't posted enough of the code for a solution to be provided. The answer depends on the package names in each case. — user207421
– user207421, Commented Jul 15, 2016 at 4:01

VGR · Accepted Answer · 2016-07-15 03:21:54Z

3

Have a look at the syntax for the java command:

java [options] classname [args]

Anything after the class name is not an option to the java command—it is simply passed as is, in a String array, to the program’s main method.

You can solve your problem by changing your final command from this:

java pgm10a -cp C:\NNK\pack2

to this:

java -cp .;C:\NNK\pack2 pgm10a

The classpath is a sequence of directories, separated by ; when running in Windows (: on other operating systems), which tell the java command where to find compiled classes. If you only specify C:\NNK\pack2, Java will only be able to see classes in that directory. The period (.) refers to the current directory, so the above classpath is pointing to both the current directory (which contains pgm10a) and the pack2 directory (which contains pgm10b).

edited Jul 15, 2016 at 3:21

answered Jul 15, 2016 at 2:59

VGR

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4 Comments

Nn Karthik Over a year ago

it removed the class not found error. but gives a new error as could not find or load main class pgm10a. what is the problem now?? I know its beyond the scope of my question.

VGR Over a year ago

You need both directories in your classpath. I’ve updated my answer accordingly.

Nn Karthik Over a year ago

@VGR thanks it worked!!but can you explain what you have done, how adding just .; solved the problem.

VGR Over a year ago

Explanation added to answer.

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