treemap

How to sort data that’s in a Java HashMap (using a TreeMap)

Here’s a brief example of how to sort data that’s already in a Java HashMap. First, some HashMap data:

import java.util.*;

Map<Integer, Float> playMap = new HashMap<Integer, Float>() {{
    put(10,  1f);
    put(12,  2f);
    put(15,  4f);
    put(18,  6f);
    put(20,  6f);
    put(25,  7f);
    put(30,  6f);
    put(35,  5f);
    put(40,  5f);
}};

A HashMap won’t keep that data in sorted order, so if you want your data sorted, one way to sort it is to add the elements to a Java TreeMap:

A Java JFreeChart x/y plot/chart/graph example

In an effort to share some source code (but without taking the time to explain it), here’s some Java source code that I just used to create a JFreeChart chart/graph of some data that I use in my Android football game: