Sorting a map by date key in Java

Question

I\'m trying to sort a map in java by date key using TreeMap. Here\'s my code

public static void sort() {

    BufferedReader br;
    String line;
    String[] da         


        

Answer 1

See http://docs.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html.

Use y for year, M for month in year, and d for day in month. Specifically, lowercase m is minute in hour, while uppercase M is month in year.

Answer 2

It looks like the lines

data = line.split(":"); map.put(df.parse(data[1]), line);

Are effectively parsing out only the month. Line.split(":") is going to produce an array split by : . If you have dates formatted in your data file dd:mm:yyyy then the resulting array "data" should be {[dd], [mm], [yyyy]}. So data[1] is going to simply be the month.

I could be wrong, but I suspect this is why you are only getting the 12 key-value pairs; you are parsing only for the month, and any time you get a new month key, you're overwriting the old key.