Java File Name Printing

Question

I am trying to print name of files from two folders, and this code compiles but not giving anything on running it.

The main target here is to find common name files in two folders, I have stored file names in two arrays and then i will applying sorting and will find common files.

 package javaapplication13;

    import java.io.File;
    import java.util.*;

    public class ListFiles1 

    {

        public static void main(String[] args) 
        {

            String path1 = "C:/"; 
            String path2 = "D:/"; 

            File folder1 = new File(path1);
            File folder2 = new File(path2);

            String[] f1=folder1.list();

            File[] listOfFiles1 = folder1.listFiles(); 
            File[] listOfFiles2 = folder2.listFiles(); 

            ArrayList<String> fileNames1 = new ArrayList<>();
            ArrayList<String> fileNames2 = new ArrayList<>();

            for (int i = 0; i < listOfFiles1.length; i++) 
            {

                if (listOfFiles1[i].isFile()) 
                {
                    fileNames1.add(listOfFiles1[i].getName());//wow
                    System.out.println(listOfFiles1[i].getName());
                }

            }

            for (int i = 0; i < listOfFiles2.length; i++) 
            {

                if (listOfFiles2[i].isFile()) 
                {
                    fileNames2.add(listOfFiles2[i].getName());//seriously wow
                }
            }

        }
    }

So from the code I helped with from the other day, you never wrote anything else...? — But I'm Not A Wrapper Class, Oct 31 '13 at 18:33
have you debugged it, to see if you get in your loops as expected, etc? — Andrew, Oct 31 '13 at 18:34
http://stackoverflow.com/questions/19662384/comparing-file-names/19662452#19662452 — But I'm Not A Wrapper Class, Oct 31 '13 at 18:36
Well, do you have files in c:/ and d:/? It seems you don't. How about learning to use a debugger, or even add some System.out.println in the source code to see what happens at every step? — JB Nizet, Oct 31 '13 at 18:38
I have run this and it works fine on my machine. Is there some other expected output you're looking for? Question is unclear. — Tom Swifty, Oct 31 '13 at 18:40

score 0 · Answer 1 · answered Oct 31 '13 at 18:49

The main target here is to find common name files in two folders, I have stored file names in two arrays and then i will applying sorting and will find common files.

I don't like the two array thing. Also, a duplicate file should probably have the same length as well as the same name. If you are really going for just names, you can remove the f.length() == temp.length() part of the condition.

private static void findDups(String dirName1, String dirName2){
    File dir1 = new File(dirName1);
    File dir2 = new File(dirName2);
    Map<String,File> fileMap = new HashMap<String,File>();
    File[] files = dir1.listFiles();
    for(File f : files){
        fileMap.put(f.getName(),f);
    }

    files = dir2.listFiles();
    StringBuilder sb = new StringBuilder(100);

    for(File f : files){
        File temp = fileMap.get(f.getName());
        if(temp != null && f.length() == temp.length()){
            sb.append("Found duplicate files:  ")
              .append(temp.getAbsolutePath())
              .append(" and ")
              .append(f.getAbsolutePath());
            System.out.println(sb);
            sb.delete(0,sb.length());
        }
    }
}

This is good code, but he seems new to Java so learning this way for him isn't the best. — But I'm Not A Wrapper Class, Oct 31 '13 at 19:02
@MadConan : A lot of things in it are over my mind... Still Thanks — Shubham, Nov 01 '13 at 15:27

score 0 · Accepted Answer · edited May 23 '17 at 10:25

Loop through both the ArrayLists you have. Each ArrayList contains the file names as it is. You'll need a nested loop (a loop inside a loop). In the core of the nested loops, you want to do a compare between current position of each ArrayList. You can use .equals() method for this. The pseudo code is something like:

//create a new ArrayList called "commonNameList"
// loop through fileNames1 with position variable "i"
    //loop through fileNames2 with position variable "j"
        //tempFileName1  = fileNames1.get(i)
        //tempFileName2 = fileNames2.get(j)
        //if tempFileName1  equals tempFileName2
            //commonNameList.add(tempFileName1)

Check these out:

http://mathbits.com/MathBits/Java/Looping/NestedFor.htm

Simple nested for loop example

How do I compare strings in Java?

Bhaijaan, thanks a lot... Kindly enlighten me... I haven't code in last 8 months... I have nearly forget everything.... Help me from where to start... — Shubham, Oct 31 '13 at 19:23
Teek ha yar. Mere urdu/hindi both harab. Mujah maaf karo. |=^] — But I'm Not A Wrapper Class, Oct 31 '13 at 19:25

Java File Name Printing

2 Answers2