Advanced string array sorting code

[Telmessos Kahin]

Hi all,

I have a string array in Java. I need to sort it by the number of character "a"s within the word (decreasing order). If some words contain same number of character "a", then I need to sort those words by their lengths(decreasing order). And if the length is same, then alphabetically.

Example array:

["aaaasd","a","aab","aaaabcd","ef","cssssssd","fdz" ,"kf","zc","lklklklklklk","l"]

needs to be sorted like:

["aaaabcd","aaaasd","aab","a","lklklklklklk","cssss ssd","fdz","ef","kf","zc","l"]

I am a beginner in Java and I don't have any idea how to make. Anyone can help?

Thanks in advance

[Stefan Evans]

You must have SOME idea of how to start.

How about this. Given a String, can you tell how many times the letter 'a' occurs in it?
Write some code (preferably a method) to do that.

[Telmessos Kahin]

I can loop the array to find the number of "a"s in the words. But I don't know how to continue. Plus I am a newbie in Java I don't know if this is a good way to do in Java and if there are some built-in functions which I can use to solve this problem. That's why I am asking here to get some practical ideas about sorting.

[Campbell Ritchie]

Welcome to the Ranch

That is an unusual sorting method, so you won't find any ready‑made methods. There is something useful about object ordering in the Java™ Tutorials.

[Telmessos Kahin]

I've already read the documentation and tried to understand how I can use comparable, made some searches on the different forums but haven't found a solution for my problem. That's why I am asking for help here telling the exact problem that I have to solve.

[Stefan Evans]

Using comparable sounds like a great solution to me.

Can you show us what you have so far?
What does your solution for counting the number of 'a's in a word look like?

[Telmessos Kahin]

Hi,

I found the solution. Posting here if someone else needs in the future.

Thanks

String[] dummy_data_string = {"aaaasd","a","aab","aaaabcd","ef","cssssssd","fdz" ,"kf","zc","lklklklklklk","l"}; 
		Arrays.sort(dummy_data_string, new Comparator<String>() {
		    public int compare(String o1, String o2) {
		        if (countA(o1) == countA(o2)) {
		            if (o1.length() == o2.length()) {
		                // 
		                return o2.compareTo(o1);
		            }
		            // uzunluk sirala
		            return o2.length() - o1.length();
		        }
		        // a harfi sayisina gore sirala
		        return countA(o2) - countA(o1);
		    }

		    private int countA(String s) {
		        int total = 0;
		        for (int pos = 0; pos < s.length(); ++pos) {
		            if (s.charAt(pos) == 'a') {
		                total++;
		            }
		        }
		        return total;
		    }
		});
		System.out.println(Arrays.toString(dummy_data_string));

[Campbell Ritchie]

Well done, but you are repeating code there. You can improve that by removing the repetition.

[Winston Gutkowski]

Telmessos Kahin wrote:I found the solution. Posting here if someone else needs in the future.

Very well done! (I hope it's you own work )

And thanks for posting it too. Have a cow.

A small nitpick: String.compareTo() already checks lengths, so I doubt that you have to.

Winston

[Winston Gutkowski]

Telmessos Kahin wrote:I found the solution...

Another minor point: Comparators are useful things, and I often find myself re-using ones I wrote earlier; but in order to do that you have to make them a named class.

How about breaking out that anonymous class and creating a FrequencyComparator that can compare the occurrences of ANY character in a String, not just an 'a'?

HIH

Winston