Question

import java.io.File;


public class filesinDirectory {

public static void main(String[] args) {
    File path = new File("/home/vito/Desktop/Dir1");
    File[] files = path.listFiles();
    int length = files.length; // line 9

    for (int i = 0; i != length; i++) {
        if (files[i].isFile()) 
        System.out.println( i + ": " + files[i].getName());
    }
}
}

With the above code, every time I try to run it I get a java.lang.NullPointerException error on line 9. However I am not sure what the source of this error is.

Answer 1

Javadoc says:

File.listFiles()

Returns:
    An array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname. The array will be empty if the directory is empty. Returns null if this abstract pathname does not denote a directory, or 

if an I/O error occurs.

So either the directory does not exist or an I/O error occured.