Bill F Bill F - 6 months ago 19
Java Question

Sorting a HashMap by date

In a Java class I have a method to reOrder an existing HashMap by date. The HashMap is of a type

<String, Object>
where the Object contains a field called expPayDate and the key string is a sequential number turned into a string.. So I need to loop through the items in the sourceMap and find the item with the newest date then copy it to a tempMap in the correct order. My issue is what is the best way to determine the item with the newest date.

Answer

Use a TreeMap instead of HashMap. it will be sorted automatically on insertion.

Map< Date, Object> m = new TreeMap< Date, Object>();

Alternatively, if you have an existing HashMap and want to create a TreeMap based on it, pass it to the constructor:

Map< Date, Object> sortedMap = new TreeMap< Date, Object>(m);

Hope it will help you.