JUnit testing returns an error

[thatos]

I have the class TableCollection which creates tables for data store in the given direcoty, the method which reads this goes like this.

public void read(String dirname,String regex) throws IOException{

where dirname is the directory name and regex is a regular expression which allows the read method to only take files in that directory which matches that expression.
On my JUnit testing I have the following test:
The test tests whether the path or directory is valid or not

  @Test  //2 
  
  public void testPathInvalid() throws IOException {
    TableCollection all = new TableCollection();
    try {
      all.read("junk/file","");
    } 
    catch
      (FileNotFoundException e) {
      return;
    }
    fail("FileNotFoundException expected");
    
  }

//This returns the following error
 java.lang.NullPointerException from line:61 i.e all.read("junk/file","");

On my read method must I include statements which firsts check whether the path in valid or not and throws an exception?

[thatos]

I found the solution to this, I placed the following statements on the read method

    File directory = new File(dirname);
    boolean exists = directory.exists();
    if(!exists){
      throw new FileNotFoundException();
    }