Null pointer exception when navigating though a folder

Question

I have to search for a file in a directory in which some sub directories exist.When im navigating through a sub directory(to which access is denied) im getting a Null Pointer Exception. CanRead() function is returning true.Plz help me out...

Answer 1

package com.cynosure.util;
import java.io.*;
import java.util.*;
import java.util.zip.*;
public class Finder {
          String path;
          String expr;
          public Finder(String path, String expr){
               this.path = path;
               this.expr = expr;
               List l = new ArrayList();
               findFile(new File(path), l);
               for (Iterator it = l.iterator(); it.hasNext();) {
                    System.out.println(it.next());
     public static void main(String[] args) throws Exception {
               new Finder(args[0], args[1]);
      void findFile(File f, List r) {
          System.out.println("Checking: "+f+": "+f.canWrite());
          if ((f.isDirectory()) && (f.canRead())) {
               File[] files = f.listFiles(new Filter("exe", true));
               for (int i = 0; i < files.length; i++) findFile(files, r);
          } else if (accept(f + "") ) {
               System.out.println("File added: "+f);
               r.add(f);
          public boolean accept(String t){
                    return t.endsWith(expr);
*Here is the code . I have passed c: and winword.exe as arguments*
*The following Exception is thrown*
+Checking: c:\System Volume Information: true+
+Exception in thread "main" java.lang.NullPointerException+
        +at com.cynosure.util.Finder.findFile(Finder.java:32)+
        +at com.cynosure.util.Finder.findFile(Finder.java:32)+
        +at com.cynosure.util.Finder.<init>(Finder.java:15)+
        +at com.cynosure.util.Finder.main(Finder.java:23)+