CODEWITHSUNDEEP
java
Osca
Osca

Reputation: 1694

read files from a directory to a list

I'm new to Java and I stuck in a practice. The practice asked me to load the images from a directory and save them to a list. I have to complete the load method in the below code and not changing the loadLibrary method. I understood that I need to read the images to allShreds but I cannot figure out the right syntax. I also read the Java documentation but didn't find the examples useful.

import java.util.*;
import java.io.*;
import java.nio.file.*;
import javax.imageio.ImageIO;

public class DeShredder {
    private List<Shred> allShreds = new ArrayList<Shred>();

    public void loadLibrary(){
        Path filePath = Path.of(UIFileChooser.open("Choose first shred in directory"));
        Path directory = filePath.getParent(); //subPath(0, filePath.getNameCount()-1);
        int count=1;
        while(Files.exists(directory.resolve(count+".png"))){ count++; }
        count = count-1;
        load(directory, count); 
        display();
    }

    /** 
     * Empties out all the current lists (the list of all shreds, 
     * the working strip, and the completed strips). 
     * Loads the library of shreds into the allShreds list. 
     * Parameters are the directory containing the shred images and the number of shreds. * Each new Shred needs the directory and the number/id of the shred. 
     */
    public void load(Path dir, int count) {
        allShreds.clear();
    }
}

The Shred class

public class Shred{

    public static final double SIZE = 40;
    private String filename;
    private int id;            // ID of the shred

    public Shred(Path dir, int id){
        filename = dir.resolve(id+".png").toString();
        this.id = id;
    }

    public void draw(double left, double top){
        UI.drawImage(filename, left, top, SIZE, SIZE);
    }

    public void drawWithBorder(double left, double top){
        UI.drawImage(filename, left, top, SIZE, SIZE);
        UI.drawRect(left, top, SIZE, SIZE);
    }

    public String toString(){
        return "ID:"+id;
    }

}

Upvotes: 2

Views: 142

Answers (2)

UkFLSUI
UkFLSUI

Reputation: 5672

In your example, allShreds is an ArrayList containing Shred objects. The correct way for adding objects to Arraylist is calling the add method with appropriate object. In your case, you need to add Shred object to the ArrayList.

And, from your question, by Loads the library of shreds into the allShreds list, it is meant that, you only need to load the Shred into the list. Your display method will then do the rest of the work for drawing and displaying images.

So, basically you just have to loop through all the image id in the directory and create new Shred from that image id and directory. And, add each of the Shred to the list:

public void load(Path dir, int count) {
    allShreds.clear();

    for (int i = 1; i <= count; i++) {
        allShreds.add(new Shred(dir, i));
    }
}

About the query from your comment:

Can you please also explain what does while in loadLibrary do ?

while(Files.exists(directory.resolve(count+".png"))){ count++; }

Here, it seems that, for the given test, in the given directory, always there need to have files in this sequence - 1.png, 2.png, 3.png, etc.

Now, inside the while loop, at first value of count is 1 and directory.resolve(count+".png") returns the absolute path of 1.png inside that directory. Then Files.exists() check if the path containing 1.png really exists, which means if the file 1.png really exists inside the given directory. If it exists, then the loop proceeds, the value of count becomes 2 and again it checks if 2.png exists in given directory and so on until it finds a [count].png which doesn't exist in that directory.

Upvotes: 1

user7571491
user7571491

Reputation:

This is little confusing. Your practice question reads: ".. I have to complete the load method in the below code and not changing the loadLibrary method".

  • neither 'load' or 'loadeLibrary' is static. So assumption is the way you use DeShredder is following:
DeShreder deShreder = new DeShreder();
deShreder.loadLibrary(); //This would call `load`
  • If you do not change loadLibrary method, actual choice of directory lies with loadLibrary. That means directory is already chosen. So why signature of load includes dir? What is the point of count parameter?
  • Who decides how to write Shred class or is it already written?
  • If you are to write it, should it not contain error handling because it may not be able to resolve the file?

There are few more questions but I think you get the point. I think the practice (question) is still not clear to you or it is pretty unfair.

Upvotes: 0

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