Java error - bad source file: file does not contain class x . Please remove or make sure it appears

Question

Recently started studying Java for an exam.

While learning packages, tried this and got an error message. What I did was

---

//Creating class A (Within package the package: com.test.helpers)
    
package com.test.helpers;
public class A {
    public void sayHello(){
        System.out.println("Hello World");
    }
}

---

//And then the class App utilising the class A
    
import com.test.helpers.*;

public class App{
  public static void main(String args[]){
    A a = new A();
    a.sayHello();
  }
}

---

I had both of these files in a directory called 'JavaTest' (on Windows 7), and first compiled the A.java using the command javac -d . A.java

And then, while attempting to compile App.java, I got the following error message:

---

App.java:5: error: cannot access A
                A a = new A();
                ^
bad source file: .\A.java
  file does not contain class A
  Please remove or make sure it appears in the correct subdirectory of the source path.
1 error

---

However, the problem seems to resolve in two ways,

1. Deleting the Source file A.java
2. Changing the import statement from import com.test.helpers.*; to import com.test.helpers.A in the file App.java.

I'd be highly grateful if you can explain what happens here. Or I might be making a goofy human mistake or a syntax error.

Here's the link to the source files

Solution 1

Hi the problem here is that the JVM confuses the class file due to the ambiguous class file name in both the directory (the JavaTest as well as the com.test.helpers directory).

when you do javac -d . A.java the compiler makes a class file in the directory com.test.helpers and now it confuses it with the sourcefile there in JavaTest

1. Deleting the Source file A.java

When you delete the source file A.java from JavaTest, JVM knows now that the class file in com.test.... is to be used, ambiguity goes away.

2. Changing the import statement from 'import com.test.helpers.*;' to 'import com.test.helpers.A' in the file, 'App.java'.

Here you are specifying which particular file to use in your class implementation that is you are telling the compiler to use the file A.java from com.test... and not from JavaTest package

Now, the solution for this ambiguity to not ever be a problem for you, you must import the specific files with import statement i.e. import com.test.helpers.A; or if you want to do import com.test.helpers.*; then you must specifically use com.test.helpers.A in place of A everywhere in your current class implementation to tell the compiler not to confuse it with the source at JavaTest

I know it's a lot late for this particular answer, but I wanted to share my views for the upcoming readers, if it could help them in any way, it would be great. Thanks!

Solution 2

move the A.java under folder JavaTest to com/test/helpers. the error you are seeing is for the compiler complaining that A.java is in a folder that does not match its package declaration. Remember, you cannot access A from App without A being in a package.

from under src driectory run the following command to compile your classes

src> javac ./*.java ./com/test/helpers/*.java

then from under src folder

src>java App

that should run your program.

Solution 3

the file A.java should be in the path JavaTest\com\test\helpers\A.java

and don't forget to compile it like this: javac -d . com\test\helpers\A.java

Solution 4

I have the same problem finally,

I was solved.

//Use like this
import com.test.helpers.A;

If u have a more than class in com.test.helpers then u can use import com.test.helpers.*;

View more solutions

Comments

[user3210872]

Thank you, that works perfectly. And do you have any idea why the error never appears when the import statement in the App.java changed from codeimport com.test.helpers.*;code to codeimport com.test.helpers.A;code ?

[jambriz]

honestly i dont know, but my guess is it has something to do with the internals of the classloader. as the A.class ended up in the right path it had no trouble finding it, and it's somehow different with the wildcard *. but as i said, this is just a guess, if i find out the exact reason i'll gladly share ( btw, if it solved your problem dont forget to accept the answer ;) )

[user3210872]

Thank you. The main thing I'm wondering is why the program worked with A.java source file in the wrong folder, but with import statement using the class name explicitly, instead of wildcard * ? Any explanation highly appreciated.

[user3210872]

Than you. However, the main reason for putting up this question here is to get an explanation as to why the program worked with A.java source file in the wrong folder, but with import statement using the class name explicitly, instead of wildcard * ?

[Py-Coder]

If i solved your problem please accept it @user3210872 bro