Sort arraylist in android date and others string

Question

I have an arraylist with the following string.

Tuesday, Thursday, Monday, Saturday.

And I want to appear sorted like:

Monday, Tuesday, Thursday, Saturday.

It is possible that appears Sunday, Wednesday..

And I have an arraylist with the following String.

dog, rabbit, cow, duck, cat.

And I want to appear sorted like:

rabbit, cat, cow, duck, dog.

Is it possible? Thank you.

Robadob · Accepted Answer · 2013-08-15 14:36:42Z

7

Yes, you should make a Comparator for each. Docs

public final class MyComparator implements Comparator<String>
{
    @Override
    public int compare(String a, String b)
    {
        //Return +1 if a>b, -1 if a<b, 0 if equal
    }
}

For your days of the week you might want to make your comparator similar to this;

public final class MyComparator implements Comparator<String>
{
    private String[] items ={
        "monday",
        "tuesday",
        "wednesday",
        "thursday",
        "friday",
        "saturday",
        "sunday"
    };
    @Override
    public int compare(String a, String b)
    {
        int ai = items.length, bi=items.length;
        for(int i = 0; i<items.length; i++)
        {
            if(items[i].equalsIgnoreCase(a))
                ai=i;
            if(items[i].equalsIgnoreCase(b))
                bi=i;
        }
        return ai-bi;
    }
}

Then to sort your arraylist according to your custom order;

MyComparator myComparator = new MyComparator();
Collections.sort(myArrayList, myComparator);

You can call Collections.sort() without the 2nd parameter if you need the default ordering of the type (If it implements comparable). Docs

edited Aug 15, 2013 at 14:36

answered Aug 15, 2013 at 13:38

Robadob

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14 Comments

Robadob Over a year ago

You define the comparison whether a is less than b, inside the compare method. I've provided an example of one of the possible implementations to do this.

But I'm Not A Wrapper Class Over a year ago

Updated, now the answer should make more sense to @JuanA.Doval

Robadob Over a year ago

Yeah, i removed the additional comment part, easy mistakes when writing code without compiling/running. Thanks

Robadob Over a year ago

@JuanA.Doval Your title says sorting of android date? If your formatting strings from date objects, you would be best to sort the list of dates using default comparator. And then produce the strings from the sorted list.

Robadob Over a year ago

@JuanA.Doval It's quite possible that accent's cause the equality to screwup, would have to find a different equality check if that turns out to be true. I don't understand your word valorate.

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