how to search for a file in windows using java

Question

i want to search for a file in windows just by giving the name of the file,intially i tried to list out all files using this piece of code

File[] files = File.listRoots();   
for(File f : files){   
  parseAllFiles(f.getPath());   
}   


...

public static void parseAllFiles(String parentDirectory){   
  File[] filesInDirectory = new File(parentDirectory).listFiles();   
  for(File f : filesInDirectory){   
    if(f.isDirectory()){   
      parseAllFiles(f.getAbsolutePath());   
    }   
    System.out.println("Current File -> " + f);             
  }     
}

but I got an exception saying

Exception in thread "main" java.lang.NullPointerException
    at fileoper.parseAllFiles(fileoper.java:24)
    at fileoper.parseAllFiles(fileoper.java:26)
    at fileoper.parseAllFiles(fileoper.java:26)
    at fileoper.main(fileoper.java:19)

Any suggestions on this?

Answer 1

I tried your example. I get a null pointer when trying to open /root. When I try to open it via terminal, it just says that I don't have the permissions.

So you basically have a problem with permissions.

The javadoc says :

̀Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.

In order to catch this, you should check if filesInDirectory is null.

public static void parseAllFiles(String parentDirectory){   
  File[] filesInDirectory = new File(parentDirectory).listFiles();
  //Added this line.
  if(filesInDirectory != null){   
    for(File f : filesInDirectory){   
      if(f.isDirectory()){   
        parseAllFiles(f.getAbsolutePath());   
      }   
      System.out.println("Current File -> " + f);             
    }
  }
}