How to properly pass function parameters?

Question

Currently I have the code like below:

    public boolean accept(File dir, String filename) {
        ...
        return filename.contains(".png") || filename.contains(".jpg") || file.isDirectory();

(the full code can be found there - https://stackoverflow.com/a/18523047/604388)

So, .png and .jpg are hardcoded now. I would like to make it as function parameter(s) and allow to pass several extensions, not just one. How could I do it?

I think I can pass list of extensions as array, but how could I perform all these checks (filename.contains()) for all array elements?

Given to pass the list of extensions as an array, as you suggest, is there a reason why the simple approach, to iterate over the array, wouldnt work? — vikingsteve, Oct 12 '13 at 09:05
@LA_ Please put the real code. You cannot embedd one method in another only if you do it by declaring it into an anonymus class. Is this the case? — Ioan, Oct 12 '13 at 09:20
@loan, I've added the link to the full code and edited the initial code to avoid the confusion. Sorry for having wrong code before. — LA_, Oct 12 '13 at 09:25

aga · Answer 1 · 2013-10-12T11:23:58.803

2

The easiest approach I can come up with is to iterate through array of extensions:

boolean res = false;
for (String ext: extensions) {
    if (filename.endsWith(ext)) {
        res = true;
    }
}

edited Oct 12 '13 at 11:23

answered Oct 12 '13 at 09:09

aga

27,954
13
86
121

1

.contains() is not proper way to check extension, you can check with .endsWith() method – nullptr Oct 12 '13 at 09:30

Steph · Answer 2 · 2013-10-12T09:40:20.680

1

No built-in answer here I fear, so iterate will be the good old solution:

boolean result = false;
for (String extension : extensions) {
    if (filename.contains(extension)) {
        result = true;
        break;
    }
}
return result || file.isDirectory();

extensions may be a String[] or a Collection<String>

Note : Better, yet, to use endsWith() rather than contains() for extensions. But I used the same condition as OP...

edited Oct 12 '13 at 09:40

answered Oct 12 '13 at 09:10

Steph

1,989
14
18

.contains is not proper method to check for extension. – nullptr Oct 12 '13 at 09:29
I agree but it is not the point. He wanted to know how to handle his parameters, and he used contains(). With endsWith() it is more correct, but functionnally different. – Steph Oct 12 '13 at 09:33

ssantos · Answer 3 · 2013-10-12T09:25:41.260

1

You should consider using an enum to avoid hardcoding.-

public enum Extension {
    PNG     (".png"),
    JPG     (".jpg");

    private String suffix;

    Extension(String suffix) {
        this.suffix = suffix;
    }

    public String getSuffix() {
        return suffix;
    }
}

Your code would look like this.-

public boolean accept(File dir, String filename, Extension... extensions) {
    boolean res = file.isDirectory();

    if (!res) {
        for (int i = 0; i < extensions.length; i ++) {
            res = res || filename.contains(extensions[i].getSuffix());
        }
    }

    return res;
}

edited Oct 12 '13 at 09:25

answered Oct 12 '13 at 09:10

ssantos

16,001
7
50
70

What does this enum offer over the strings? – Eric Oct 12 '13 at 09:11
Your function has to return `File[]` whilst it returns `boolean` value. – aga Oct 12 '13 at 09:14
1

Well, it keeps the hardcode values "under control", so that the rest of application can safely call the enum types. – ssantos Oct 12 '13 at 09:14
Thanks, @ssantos. I've edited the question, there is no problem with returning `boolean` - I haven't copied the full code initially. – LA_ Oct 12 '13 at 09:17
Ok, just edited my answer, I guess that's what you're looking for. – ssantos Oct 12 '13 at 09:20

Ioan · Accepted Answer · 2013-10-12T09:16:38.057

0

You can use the below snippet which should be enough for your needs :

private boolean loadFileList(String directory, String...extensions){
    for (String extension : extensions){
        if (filename.contains(extension))
            return true;
    }
    return false;
}

P.S. I'm not sure what is the filename type, but if returns boolean then the above example should fit

edited Oct 12 '13 at 09:16

answered Oct 12 '13 at 09:10

Ioan

5,152
3
31
50

Pretty sure `true` does not match the type `file[]` – Eric Oct 12 '13 at 09:10
Really ? Well I copied his method signature from the question. As long the question doesn't have any downvote, I cannot understand why you downvoted me. – Ioan Oct 12 '13 at 09:12
@Eric: I agree with loan, it is the OP that made a mistake in his return type. If it is the reason of the doynvote on his answer and/or mine, I think you are mistaken – Steph Oct 12 '13 at 09:16
@Eric feel better you downvoted one question and two answers ? You should have a look at other answers too. – Ioan Oct 12 '13 at 09:18

nullptr · Answer 5 · 2013-10-12T09:28:53.873

0

import java.io.File;
import java.io.FileFilter;

public class NewClass {
    public static File[] loadFileList(String dir, FileFilter filter){
        return new File(dir).listFiles(filter);
    }

    public static void loadFiles(){
        File files[] = loadFileList("c:\\", new FileFilter() {
            public boolean accept(File pathname) {
                if(pathname.getAbsolutePath().toLowerCase().endsWith(".png")){
                    return true;
                }
                if(pathname.getAbsolutePath().toLowerCase().endsWith(".jpg")){
                    return true;
                }
                return false;
            }
        });
        // here do some DIRTY things with files....
    }
}

edited Oct 12 '13 at 09:28

answered Oct 12 '13 at 09:22

nullptr

3,320
7
35
68

you don't answer the question. Your extensions are not parameters, they are still hardcoded. – Steph Oct 12 '13 at 09:37
Thats is what I am doing, passing parameters as FileFilter... then no need to hardcode anything in loadFileList method... – nullptr Oct 12 '13 at 09:52

How to properly pass function parameters?

5 Answers5