How do use console to choose any file from a folder?

Question

I need to be able to choose any file inside a folder by input on console.

Code

Instead of a predefined like "bridge_rgb.png" I want to be able to choose any file in the folder via console input.

private void imageName() {
        System.out.println("Select your image");
        String input = scanner.next();
        if (input.equals("bridge_rgb.png")) {

        } else if (input.equals("gmit_rgb.png")) {
        
        }

        System.out.println("Image Selected");

    }

Inside my functions I want to do the same, here's the code:

File file = new File("bridge_rgb.png");
BufferedImage source = ImageIO.read(file);

// processing: result gets created

File output = new File("bridge_grey.png");
ImageIO.write(result, "png", output);

I know a GUI would make file-choosing easy, but I have to use specifically a console.

This kind of thing is impractical without a gui. Why no gui? — g00se
– g00se, Commented Aug 11, 2021 at 17:46
A GUI (graphical user-interface) would make it easier, because Java has the JFileChooser dialog, that allows listing, filtering, choosing and returns the File choosen. — hc_dev
– hc_dev, Commented Aug 11, 2021 at 18:12

hc_dev · Accepted Answer · 2021-08-11 18:01:16Z

1

Say you have specified a folder, or use the current working directory.

At least you need two ingredients:

a function which lists all files given in the folder as option to choose from
a user-interface (text-based or graphical) that allows to present those options and let the user choose from them (e.g. by hitting a number of clicking an item from a drop-down-list

List files in current directory

Search for [java] list files in directory and pick:

File[] files = directory.listFiles();

Text-based UI (TUI) to choose option by number

E.g. from How can I read input from the console using the Scanner class in Java?

// output on console
System.out.println("Choose from following files:");
for (int i=0, i < files.length(), i++) {
  System.out.println(String.format("[%d] %s", i, file.getName()); 
}

// reading the number
Scanner sc = new Scanner(System.in);
int i = sc.nextInt();

// testing if valid, within options index (0..n)
if (i < 0 || i >= files.length()) {
  System.out.println("Invalid input. Please enter a number from options.");
}
// file choosen
System.out.println("Your choice: " + file[i].getName());

// other UI operations, like display file, etc.

// IMPORTANT: always close the stream/scanner when finished
scanner.close();

answered Aug 11, 2021 at 18:01

hc_dev

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1 Comment

hc_dev Over a year ago

The listFiles method allows to pass a FilenameFilter, to list only specific files like .png images.

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How do use console to choose any file from a folder?

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List files in current directory

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List files in current directory

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