CODEWITHSUNDEEP
java
new
new

Reputation: 19

how to sort integer from listFiles?

I want to sort the integer from listFiles which not included the string. The smallest number will display"The smallest number=" and the biggest number will display"The biggest number=" 

public static void main(String[] args) {
        // TODO Auto-generated method stub
        File folder = new File("input/");
        File [] files = folder.listFiles();         

        for(int i = 0; i < files.length-1;i++) {

            String fileFullName = files[i].getName();       
            String fileSimple= fileFullName.substring(2,fileFullName.length()-4);           
            long fileNumber =Long.parseLong(fileSimple);

            String fileFullName2 = files[i+1].getName();        
            String fileSimple2= fileFullName2.substring(2,fileFullName2.length()-4);            
            long fileNumber2 =Long.parseLong(fileSimple2);                  
        }                       
    }

The file name included HR20190405.txt, AR20290405.txt,RG20290805.txt,RK21290405.txt

Upvotes: 1

Views: 66

Answers (3)

akourt
akourt

Reputation: 5563

Actually based on a previous answer, you can go even further and refine the code to use both the Stream API as well as java.nio. This will save you plenty of time as you won't be needing to perform manual iterations over the array of files you have read.

Also a good trick is to avoid the various magic number during substringing actions. A regex would have been way more suitable to avoid unwanted runtime errors.

Based on the above, a sample code would look like:

private static Optional<IntSummaryStatistics> getMinMax(final String filePath) {
    try (Stream<Path> pathStream = Files.list(Paths.get(filePath))){
        return Optional.of(pathStream
        .map(Path::getFileName)
        .map(Path::toString)
        .map(s -> s.replaceAll("\\D+",""))
        .mapToInt(Integer::valueOf)
        .summaryStatistics());
    } catch (IOException e) {
        e.printStackTrace();
    }
    return Optional.empty();
}

And calling this would as simple as doing this:

public static void main(String[] args) {
    getMinMax("D:\\test").ifPresentOrElse(
        stats -> System.out.println("Min is " + stats.getMin() + " Max is " + stats.getMax()),
        () -> System.out.println("Nothing has been found")
    );
}

Upvotes: 0

Ruslan
Ruslan

Reputation: 6290

There is suitable method summaryStatistics from IntStream. Using stream api it will look like:

IntSummaryStatistics stat = Arrays.stream(files)
        .mapToInt(file -> Integer.valueOf(file.getName().substring(2, file.getName().length() - 4)))
        .summaryStatistics();

System.out.println(stat.getMin());
System.out.println(stat.getMax());

Upvotes: 1

mbsingh
mbsingh

Reputation: 489

You were quite close. We will just have to store the maximum & minimum values in variables. Also, the code to fetch the number from file name can be a separate method:

public static void main(String[] args) {

    File folder = new File("input/");
    File [] files = folder.listFiles();      

    //Set first number as smallest and largest   
    long smallest = getNumberFromName(files[0]);
    long largest = smallest;

    //Get number for each file and assign smallest & largest values
    for(int i = 1; i < files.length-1;i++) {
        long nextNumber = getNumberFromName(files[i]);
        if (smallest > nextNumber)
            smallest = nextNumber
        if (largest < nextNumber)
            largest = nextNumber
    }
    System.out.println("The smallest number="+smallest)
    System.out.println("The biggest number="+largest)
}


private static long getNumberFromName(File nextFile) {
    String fileFullName = nextFile.getName();       
    String fileSimple= fileFullName.substring(2,fileFullName.length()-4);           
    return Long.parseLong(fileSimple);
}

Upvotes: 0

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