Ndtyjky

suppose there are different files of different types. for example razi.mp3 of size 10mb, test.txt of 5 mb, song.mp3 of 20mb, file.js of 100mb, mark.txt of 10mb, zoom.js of 50mb. I need to print file type with total size. in this case I want to print:
mp3 : 30mb
txt : 15mb
js : 150mb
Can I solve this problem by using map in java or any other solution?

Basically I want to use map with comparator interface. Any other ways are most welcome.

Any type of help and effort is very much appreciable. Thanks in advance for every one who are interesting in this problem.

Yes. you can solve this problem via map.

  public class FileMeta {



    String name;

    String extension;

    int size;



    public FileMeta(String name, String extension, int size) {

      this.name = name;

      this.extension = extension;

      this.size = size;

    }



    public String getName() {

      return name;

    }



    public FileMeta setName(String name) {

      this.name = name;

      return this;

    }



    public String getExtension() {

      return extension;

    }



    public FileMeta setExtension(String extension) {

      this.extension = extension;

      return this;

    }



    public int getSize() {

      return size;

    }



    public FileMeta setSize(int size) {

      this.size = size;

      return this;

    }



  }



  public static void main(String args) {

    Map<String, List<FileMeta>> map = new ConcurrentHashMap<>();

    FileMeta obj1 = new FileMeta("razi", "mp3", 10);

    FileMeta obj2 = new FileMeta("test", "txt", 5);

    FileMeta obj3 = new FileMeta("song", "mp3", 20);

    FileMeta obj4 = new FileMeta("file", "js", 100);

    FileMeta obj5 = new FileMeta("mark", "txt", 10);

    FileMeta obj6 = new FileMeta("zoom", "js", 50);



    putinMap(map, obj1);

    putinMap(map, obj2);

    putinMap(map, obj3);

    putinMap(map, obj4);

    putinMap(map, obj5);

    putinMap(map, obj6);



    map.entrySet().stream().forEach(entry-> {

      int size = entry.getValue().stream().mapToInt(FileMeta::getSize).sum();

      System.out.println(entry.getKey() + " : " + size + " mb");

    });





  }



  private static void putinMap(Map<String, List<FileMeta>> map, FileMeta obj) {

    if (map.containsKey(obj.getExtension())) {

      map.get(obj.getExtension()).add(obj);

    } else {

      ArrayList<FileMeta> list = new ArrayList<>();

      list.add(obj);

      map.put(obj.getExtension(), list);

    }

  }

in which key is the type of file Like mp3 or txt and value is the consist of some object which contain name and file size and extension.

you have to iterate on each row and sum of each filesize.

The following works:

import java.util.*;

public class Main {

static class FileInfo {

    private String name;

    private int sizeInMb;



    public FileInfo(String name, int sizeInMb) {

        this.name = name;

        this.sizeInMb = sizeInMb;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    public int getSizeInMb() {

        return sizeInMb;

    }



    public void setSizeInMb(int sizeInMb) {

        this.sizeInMb = sizeInMb;

    }

}



public static void main(String args) {

    List<FileInfo> fileInfos = new ArrayList<>();

    fileInfos.add(new FileInfo("razi.mp3", 10));

    fileInfos.add(new FileInfo("test.txt", 5));

    fileInfos.add(new FileInfo("song.mp3", 20));

    fileInfos.add(new FileInfo("file.js", 100));

    fileInfos.add(new FileInfo("mark.txt", 10));

    fileInfos.add(new FileInfo("zoom.js", 50));



    Map<String, Integer> sizes = new HashMap<>();



    //initiatise map

    fileInfos.forEach(fileInfo -> {

        final String extension = fileInfo.getName().substring(fileInfo.getName().lastIndexOf("."));

        sizes.put(extension, 0);

    });



    System.out.println(sizes);



    //put summaries

    fileInfos.stream().forEach(fileInfo -> {

        //get extension

        String extension = fileInfo.getName().substring(fileInfo.getName().lastIndexOf("."));

        sizes.put(extension, sizes.get(extension) + fileInfo.getSizeInMb());

    });



    System.out.println(sizes);

}

}

you can create a FileObject class with instance members as name ,inputstream , size and type.

@Getter

@Setter

public class FileObject {

   private String name;

   private InputStream inputStream;

   private String type;

   private Long size;



   public FileObject(String name, InputStream inputStream, String type, Long size) {

    this.name = name;

    this.inputStream = inputStream;

    this.type = type;

    this.size = size;

  }

}

Create array of FilObject with you data.

Then you can create a Map with type attribute as key (corrspoding inital value as 0 )and for each Fileobject add the size value to corresponding key in map.

Map<String, FileObject> fileObjectMap = new HashMap<>();

After that you will be able to print your required output.

Hope it helps.