Converting String to int but keeping the length

Question

I am trying to get file names from a directory to a String, remove the file extensions from the String so I can convert the file names to Integers (The file names are numbers, like 00123.jpg).

(I want to convert it to an int to get the average number between the largest number and the smallest number of the array)

Here's what I did so far:

File currentBoot = new File(destination); //Directory
String[] fileNames = currentBoot.list(); //Returns array of file names (Including .jpg)
for (int i = 0; i<fileNames.length;i++)
{
    fileNames[i] = fileNames[i].replace(".jpg", ""); //Removes .jpg from the file names
}

int numbers[] = new int[fileNames.length];

for (int i = 0; i<numbers.length; i++) {
    numbers[i] = Integer.parseInt(fileNames[i]); //Convert the file names to int
}

Here I add the file extension again so I can search for the file:

int max = findLargest(fileNames);
int min = arrayMin(fileNames);
int fileNumber = (max + min)/2;
String fileName = fileNumber + ".jpg";

Here's my problem: numbers[] returns the file names but removes any useless zeros (Replaces 00123 with 123).

The number of zeros on the file names changes between devices (I use a system folder with those files in it) and my app crashes at different devices because it looks for 123.jpg instead of 00123.jpg (I add the file extensions back later).

How do I convert a String to an int but keeping the leading zeros?

Answer 1

Store it in a HashMap<String, integer>

HashMap<String, int> map = new HashMap<String, int>();
for(int I = 0; I < numbers.length; I++)
    map.put(fileNames[I], Integer.parseInt(fileNames[I].replace(".jpg", "")));

Something to that effect.

Answer 2

Something like this might help:

for (int i = 0; i < fileNames.length; i++)
{
    fileNames[i] = fileNames[i].replace(".jpg", ""); //Removes .jpg from the file names
}
ZeroNum[] numbers = new ZeroNum[];
for (int i = 0; i < numbers.length; i++)
{
    numbers[i].zeros = fileNames[i].length() - Integer.toString(Integer.parseInt(fileNames[i])).length(); // total length of string minus non-zero
    numbers[i].num = Integer.parseInt(fileNames[i]);
}

class ZeroNum
{
    int num, zeros;
    public ZeroNum(int num, int zeros)
    {
        this.num = num;
        this.zeros = zeros;
    }
}

I get that this is a pretty ugly solution, but it should work...

Answer 3

By converting to an int, you've asked java to represent the String as a int value. Note, that the 'int' value of 00123 is actually 123. When you do the conversion, the extra zero's are discarded due to being, as you said, 'useless'.

If you wanted to keep them I'd recommend simply keeping them as strings and not converting them. However, perhaps you have a need so one relatively easy solution would be constructing/using a secondary array that contains the original length of each String-to-be-converted. Then, after doing your logic, use that secondary array to convert the numbers back to strings with the appropriate number of leading zeros. In this case, your secondary array could actually be the 'filenames' array.

    File currentBoot = new File(destination); //Directory
}
String[] fileNames = currentBoot.list(); //Returns array of file names (Including .jpg)

for (int i = 0; i<fileNames.length;i++) {
    fileNames[i] = fileNames[i].replace(".jpg", ""); //Removes .jpg from the file names
}

int numbers[] = new int[fileNames.length];

for (int i = 0; i<numbers.length; i++) {
    numbers[i] = Integer.parseInt(fileNames[i]); //Convert the file names to int
}

/*do your logic that required the int conversion, keeping the numbers array in the same order */

/* note, this will only keep the ORIGINAL NUMBER OF CHARACTERS in the filename by padding zeros at the front... 
 * it will NOT maintain the original number of zeros. */
String [] newFileNames = new String[numbers.length];
for (int i = 0; i<numbers.length; i++) {
    numbers[i] = Integer.parseInt(fileNames[i]); //Convert the file names to int
}

for (int i = 0; i<numbers.length; i++) { // for each number in numbers
    int numberDigits = String.valueOf(numbers[i]).length(); //  number of digits in numbers[i]
    int filenameDigits = fileNames[i].length(); // number of digits originally in the filename
    newFileNames[i] = "" + numbers[i];
    for(int zerosToAdd = filenameDigits - numberDigits; zerosToAdd>0; zerosToAdd--) {
        newFileNames[i] = "0" + newFileNames[i];  // add a zero to the front
    }
}

Obviously you could do this with an actual object that contained both the String and the filename -- and I'd say that'd likely be preferable, but this is a fast and dirty solution.

Now, note that this only adds zeros up to the original number of characters... so if fileNames[2] was 0099 got converted to numbers[2] and was just '99'... and then your logic modified that to 123... the above code would only add one zero instead of two... returning it to the 4 digits of the original filename. Clearly one could use the same logic and simply count the initial zeros in the filename (numberOfInitialZeros = fileNames[i].length-fileNames[i].replace("0","").length()) and add them back in, but I thought this was likely the more wanted solution.