是否没有通过LinkedHashMap值进行迭代？

Question

For a problem I'm designing in Java, I'm given a list of dates and winning lottery numbers. I'm supposed to do things with them, and spit them back out in order. I decided to choose a LinkedHashMap to solve it, the Date containing the date, and int[] containing the array of winning numbers.

Thing is, when I run the .values() function, I'm noticing the numbers are no longer ordered (by insertion). The code I'm running is:

    for(int i = 0; i < 30; i++){ //testing first 30 to see if ordered
        System.out.println(Arrays.toString((int [])(winningNumbers.values().toArray()[i])));
    }   

Can anyone see what exactly I'm doing wrong? Tempted almost to just use .get() and iterate through the dates, since the dates do go in some order, but that might make using a LinkedHashMap moot. Might as well be using a 2-D ArrayList[][] in that case. Thanks in advance!

EDIT: Adding code for further examination!

Lottery Class: http://pastebin.com/9ezF5U7e Text file: http://pastebin.com/iD8jm7f8

To test, call checkOldLTNums(). Just pass it any int[] array, it doesn't utilize it, at least relevant to this problem. The output is different from the first lines in the .txt, which is organized. Thanks!

EDIT2:

I think I figured out why it fails. I used a smaller .txt file, and the code worked perfectly. It might be that it isn't wise to load 1900 entries of stuff into memory. I suppose it's better to just load individual lines and compare them instead of grabbing everything at once. Is this logic sound? Any advice going from here would be useful.

Answer 1

The values() method will return the Map 's values in the same order they were inserted , that's what ordered means, don't confuse it with sorted , that means a different thing - that the items follow the ordering defined by the value's Comparator or its natural ordering if no comparator was provided.

Perhaps you'd be better off using a SortedMap that keeps the items sorted by key. To summarise: LinkedHashMap is ordered and TreeMap is sorted .

Answer 2

Try using a TreeMap instead. You should get the values in ascending key order that way.

Answer 3

I can't believe I missed this. I did some more troubleshooting, and realized some of the Date keys were replacing others. After doing some testing, I finally realized that the formatting I was using was off: "dd/MM/yyyy" instead of "MM/dd/yyyy". That's what I get for copy-pasting, haha. Thanks to all who helped!