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  4. What is the problem accessing "C" drive using a code (using import.io.*; )?

What is the problem accessing "C" drive using a code (using import.io.*; )?

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questionhelpjavaalgorithms
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  • C CoderForEver

    Hi guys, The aim of this code is to find a file by giving starting folder. The problem is, when I use "C:\\" directory it doesn't work, even I tried "C:" and "C" if it was the problem. I think the problem is related to some Access restriction. If I changed the starting folder, lets say, to "C:\\someFolder" it will work perfectly. How can I make the code work so that it will start searching from C drive .. Help me Thank you

    package ex4;

    import java.io.*;

    public class FileSearchRecursive {

    /\*\*
     \* @param args
     \*/
    public static void main(String\[\] args) {
    	FileSearchRecursive x=new FileSearchRecursive();
                if(!(x.searchForFile("C:\\\\","try.txt")))//works find if I changed the statement to 
                                                        if(!(x.searchForFile("C:\\\\someFolder","try.txt")))
    		System.out.println("File not found");
    
    }	
    	
    boolean searchForFile(String startDir,String fileName)
    {		
    			
    	File file1=new File(startDir);
    	
    	if(file1.exists())
    	{
    	File\[\] list=file1.listFiles();
    		for(File x: list)
    		{
    				
    			 if(x.isFile())
    			{					
    				if(x.getName().equals(fileName))	
    				{
    					System.out.println("I got the file "+x.getName()+" in "+x.getAbsolutePath());
    					return true;
    				}
    			}
    			 else if(x.isDirectory())
    				{
    					if(searchForFile(x.getAbsolutePath(),fileName))
    						return true;
    				}		
    			
    		}
    	}			
    	
    	
    	return false;
    }
    

    }

    L Offline
    L Offline
    Luc Pattyn
    wrote on last edited by
    #7

    Hi, some comments: 1. you should implement error handling in your code; have a try-catch and log the exception. 2. when an exception occurs, it gives the number of the offending line; that is where the problem shows itself, the actual cause may be somewhat sooner. 3. when the exception occurs in a method call, check the documentation for that method to see what it has to say about the specific exception. That should tell you exactly what is wrong. 4. Your searchForFile() method is a bit silly, it tells whether a file exists, but when it does, it does not tell you where it is. A better definition of it would return the path to the first occurence it finds as a string. :)

    Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

    Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

    1 Reply Last reply
    0
    • C CoderForEver

      It throws a NullPointerException I think it is because , the application may not have an access on hard drives, but it works if I search in folders which are located in those drives. Can you try it please?

      J Offline
      J Offline
      jschell
      wrote on last edited by
      #8

      CoderForEver wrote:

      It throws a NullPointerException

      The stack trace tells you where. So which line is it?

      CoderForEver wrote:

      the application may not have an access on hard

      Application? You are running exactly the code you posted from a console window correct? Thus the only way it wouldn't have access is if you you, the user, doesn't have permission to access the C drive root. And if that was the case then you should see an exception that indicates exactly that - a permission problem.

      1 Reply Last reply
      0
      • T TorstenH

        ...you know, you need to mask the double-slash ? it's not interpreted right otherwise. the Backslash is in Java a sign for masking and special String-values like the tab "\t". To set a "\" you always need to use 2 "\\". It's a good solution to set up a String and use this as a argument for the following commands:

        FileSearchRecursive x=new FileSearchRecursive();
        String strSearchFolder = "C:\\\\someFolder"; // add extra slashes to make it a double slash
        String strSearchFile = "try.txt"´;
        System.out.println("Searching in folder:\t" + strSearchFolder + " for file:\t" + strSearchFile);
        if(false == (x.searchForFile(strSearchFolder,strSearchFile ))){
        System.out.println("File not found");
        }

        regards Torsten

        I never finish anyth...

        J Offline
        J Offline
        jschell
        wrote on last edited by
        #9

        TorstenH. wrote:

        ...you know, you need to mask the double-slash ?

        And do you know that the OP code doesn't need to do that correct? The code has "C:\\" which is exactly what it should have to access the C drive root.

        TorstenH. wrote:

        String strSearchFolder = "C:\\\\someFolder"; // add extra slashes to make it a double slash

        Which resolves to "C:\\someFolder" which although it will work on windows is not any better or more correct than "C:\someFolder".

        1 Reply Last reply
        0
        • C CoderForEver

          Hi guys, The aim of this code is to find a file by giving starting folder. The problem is, when I use "C:\\" directory it doesn't work, even I tried "C:" and "C" if it was the problem. I think the problem is related to some Access restriction. If I changed the starting folder, lets say, to "C:\\someFolder" it will work perfectly. How can I make the code work so that it will start searching from C drive .. Help me Thank you

          package ex4;

          import java.io.*;

          public class FileSearchRecursive {

          /\*\*
           \* @param args
           \*/
          public static void main(String\[\] args) {
          	FileSearchRecursive x=new FileSearchRecursive();
                      if(!(x.searchForFile("C:\\\\","try.txt")))//works find if I changed the statement to 
                                                              if(!(x.searchForFile("C:\\\\someFolder","try.txt")))
          		System.out.println("File not found");
          
          }	
          	
          boolean searchForFile(String startDir,String fileName)
          {		
          			
          	File file1=new File(startDir);
          	
          	if(file1.exists())
          	{
          	File\[\] list=file1.listFiles();
          		for(File x: list)
          		{
          				
          			 if(x.isFile())
          			{					
          				if(x.getName().equals(fileName))	
          				{
          					System.out.println("I got the file "+x.getName()+" in "+x.getAbsolutePath());
          					return true;
          				}
          			}
          			 else if(x.isDirectory())
          				{
          					if(searchForFile(x.getAbsolutePath(),fileName))
          						return true;
          				}		
          			
          		}
          	}			
          	
          	
          	return false;
          }
          

          }

          J Offline
          J Offline
          jschell
          wrote on last edited by
          #10

          What is the result of running the following? If it is exception then post the entire stack trace.

          File file1=new File("C:\\\\");
          System.out.println("exists=" + file1.exists());
          
          1 Reply Last reply
          0
          • C CoderForEver

            Come on guys. My question is how can I find a file in "C", not in "C:\someFolder"? ... on the latter case it works easily. If you have time try to run my code, it really works. But try to make the searching folder "C:\" not "C:\someFolder". Then it will through an exception. Though thank you for your help

            L Offline
            L Offline
            Lost User
            wrote on last edited by
            #11

            Consider these lines:

            	File\[\] list=file1.listFiles();
            		for(File x: list)
            

            if file1.listfiles() does not return any items then list will be null and the runtime will throw an exception. Took me less than 5 minutes to find it with the debugger. Lesson: Check return values and statuses, and catch exceptions: there is no alternative.

            The best things in life are not things.

            1 Reply Last reply
            0
            • C CoderForEver

              Hi guys, The aim of this code is to find a file by giving starting folder. The problem is, when I use "C:\\" directory it doesn't work, even I tried "C:" and "C" if it was the problem. I think the problem is related to some Access restriction. If I changed the starting folder, lets say, to "C:\\someFolder" it will work perfectly. How can I make the code work so that it will start searching from C drive .. Help me Thank you

              package ex4;

              import java.io.*;

              public class FileSearchRecursive {

              /\*\*
               \* @param args
               \*/
              public static void main(String\[\] args) {
              	FileSearchRecursive x=new FileSearchRecursive();
                          if(!(x.searchForFile("C:\\\\","try.txt")))//works find if I changed the statement to 
                                                                  if(!(x.searchForFile("C:\\\\someFolder","try.txt")))
              		System.out.println("File not found");
              
              }	
              	
              boolean searchForFile(String startDir,String fileName)
              {		
              			
              	File file1=new File(startDir);
              	
              	if(file1.exists())
              	{
              	File\[\] list=file1.listFiles();
              		for(File x: list)
              		{
              				
              			 if(x.isFile())
              			{					
              				if(x.getName().equals(fileName))	
              				{
              					System.out.println("I got the file "+x.getName()+" in "+x.getAbsolutePath());
              					return true;
              				}
              			}
              			 else if(x.isDirectory())
              				{
              					if(searchForFile(x.getAbsolutePath(),fileName))
              						return true;
              				}		
              			
              		}
              	}			
              	
              	
              	return false;
              }
              

              }

              D Offline
              D Offline
              David Skelly
              wrote on last edited by
              #12

              This works for me. As someone else has pointed out, file1.listFiles() may return null so you need to allow for that.

              L 1 Reply Last reply
              0
              • D David Skelly

                This works for me. As someone else has pointed out, file1.listFiles() may return null so you need to allow for that.

                L Offline
                L Offline
                Lost User
                wrote on last edited by
                #13

                I am reduced to "someone else". :((

                The best things in life are not things.

                1 Reply Last reply
                0
                • L Lost User

                  Judging by your comments and code extract I would suggest the following line be changed as indicated:

                  if(!(x.searchForFile("C:\\someFolder","try.txt")))
                  // change to

                  if(!(x.searchForFile("C:\\someFolder\\","try.txt")))

                  The best things in life are not things.

                  N Offline
                  N Offline
                  Nagy Vilmos
                  wrote on last edited by
                  #14

                  This would show the original problem if C:\\someFolder was empty.


                  Panic, Chaos, Destruction. My work here is done. or "Drink. Get drunk. Fall over." - P O'H OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre Have a bit more patience with newbies. Of course some of them act dumb -- they're often *students*, for heaven's sake. -- (Terry Pratchett, alt.fan.pratchett)

                  L 1 Reply Last reply
                  0
                  • N Nagy Vilmos

                    This would show the original problem if C:\\someFolder was empty.


                    Panic, Chaos, Destruction. My work here is done. or "Drink. Get drunk. Fall over." - P O'H OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre Have a bit more patience with newbies. Of course some of them act dumb -- they're often *students*, for heaven's sake. -- (Terry Pratchett, alt.fan.pratchett)

                    L Offline
                    L Offline
                    Lost User
                    wrote on last edited by
                    #15

                    Exactly how I found the problem.

                    The best things in life are not things.

                    D 1 Reply Last reply
                    0
                    • L Lost User

                      Exactly how I found the problem.

                      The best things in life are not things.

                      D Offline
                      D Offline
                      David Skelly
                      wrote on last edited by
                      #16

                      Interesting. When I run it on an empty directory, I get a zero-length array. Also, it doesn't make any difference if I put "C:\\someFolder" or "C:\\someFolder\\". It behaves the same in both cases. I only get null back if there is some kind of problem (e.g. Access denied).

                      L 1 Reply Last reply
                      0
                      • D David Skelly

                        Interesting. When I run it on an empty directory, I get a zero-length array. Also, it doesn't make any difference if I put "C:\\someFolder" or "C:\\someFolder\\". It behaves the same in both cases. I only get null back if there is some kind of problem (e.g. Access denied).

                        L Offline
                        L Offline
                        Lost User
                        wrote on last edited by
                        #17

                        I'll try it again sometime and check the results more closely.

                        The best things in life are not things.

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