Sort a LinkedHashMap with Values and with Time Priority in case of Equal

Question

I know that this topic can be well covered, but they only use a Treemap which use only one value and in case of same value does not return what I would like.

Here is my object:

public classe myObjectToMap
{
    long id;
    double price;
    String name;
    long date;

    public static void GetMyObject(long id, double price, String name)
    {
        myObjectToMap newObject = new myObjectToMap;
        newObject.id = id;
        newObject.price = price;
        newObject.name = name;
        newObject.date = new Date().getTime();
        PlaceOfMyMap.myMap.put(id, newObject);

    }

Here is where my map is located, I put a LinkedHashMap, and I do not which is the best between Hashmap, TreeMap and LinkedHashMap, I did see that TreeMap give a comparator of Value, but I do not arrive to Compare with more than one value.

public class PlaceOfMyMap
{
    public static LinkedHashmap<Long, myObjectToMap> myMap = new LinkedHashmap<~>;
}

And finally, here is my main program:

public class MainClass
{
    public static void main(String args[]) throws Exception
    {
        MyObjectToHashmap.GetMyObject(1, 26, "Mat")
        MyObjectToHashmap.GetMyObject(4, 25, "Tommy")
        MyObjectToHashmap.GetMyObject(16, 24, "Kate")
        MyObjectToHashmap.GetMyObject(63, 26, "Mary")
        MyObjectToHashmap.GetMyObject(99, 24, "Ronny")

 }

}

First: I would like to sort them from the highest price to the lowest with a time priority, which means that I would like to Mat being the first and Kate the second.

Second: I would like to sort them from the Lowest price to the the Highest with a time priority which means that I would like to Kate being the first and Ronny the second.

Any tips to sort them correctly ?

Yes, use different structures for your problem. If you want a fast access to each data, use `HashMap`. If you need them sorted by two ways, use a `PriorityQueue` with a `Comparator`, one per sort behavior. — Luiggi Mendoza, Jul 16 '14 at 15:50
Ok, But I do not really know how the Object PriorityQueue is working, can we store any object inside and find it again with a key ? Or is it a more list ? — Thomas Th., Jul 16 '14 at 16:07
[`PriorityQueue`](http://docs.oracle.com/javase/8/docs/api/java/util/PriorityQueue.html). — Luiggi Mendoza, Jul 16 '14 at 16:09

Syam S · Accepted Answer · 2014-07-16T17:23:40.113

Try the below code. You can reverse the compare() method to get reverse sorting

import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

class MyObject
{
    private long id;
    private double price;
    private String name;
    private long date;

    public MyObject(long id, double price, String name) {
    this.id = id;
    this.price = price;
    this.name = name;
    this.date = new Date().getTime();
    }

    @Override
    public String toString() {
        return "MyObject [id=" + id + ", price=" + price + ", name=" + name
                + "]";
    }

    public double getPrice() {
        return price;
    }
    public long getDate() {
        return date;
    }
}

public class MapSort {

    public static void main(String[] args) {
        Map<Long, MyObject> myMap = new LinkedHashMap<Long, MyObject>();

        myMap.put(1L, new MyObject(1, 26, "Mat"));
        myMap.put(4L, new MyObject(4, 25, "Tommy"));
        myMap.put(16L, new MyObject(16, 24, "Kate"));
        myMap.put(63L, new MyObject(63, 26, "Mary"));
        myMap.put(99L, new MyObject(99, 24, "Ronny"));

        System.out.println("Before Sorting");
        System.out.println(myMap);
        System.out.println("\nAfter Sorting");
        System.out.println(sortMap(myMap));
    }

    private static Map<Long, MyObject> sortMap(
            Map<Long, MyObject> unsortedMap) {

        List<Entry<Long, MyObject>> list = new LinkedList<Entry<Long, MyObject>>(unsortedMap.entrySet());

        Collections.sort(list,
                new Comparator<Entry<Long, MyObject>>() {

                    @Override
                    public int compare(Entry<Long, MyObject> o1, Entry<Long, MyObject> o2) {
                        int priceResult = Double.valueOf(o1.getValue().getPrice()).compareTo(Double.valueOf(o2.getValue().getPrice()));
                        if(priceResult != 0) return priceResult;
                        return Long.valueOf(o1.getValue().getDate()).compareTo(Long.valueOf(o2.getValue().getDate()));
                    }
                });

        Map<Long, MyObject> sortedMap = new LinkedHashMap<Long, MyObject>();
        for(Entry<Long, MyObject> item : list){
            sortedMap.put(item.getKey(), item.getValue());
        }
        return sortedMap;
    }
}

Output

Before Sorting
{1=MyObject [id=1, price=26.0, name=Mat], 4=MyObject [id=4, price=25.0, name=Tommy], 16=MyObject [id=16, price=24.0, name=Kate], 63=MyObject [id=63, price=26.0, name=Mary], 99=MyObject [id=99, price=24.0, name=Ronny]}

After Sorting
{16=MyObject [id=16, price=24.0, name=Kate], 99=MyObject [id=99, price=24.0, name=Ronny], 4=MyObject [id=4, price=25.0, name=Tommy], 1=MyObject [id=1, price=26.0, name=Mat], 63=MyObject [id=63, price=26.0, name=Mary]}

It does sort in ascending order of price first and then time. Verify the system outs. It works fine for me. Updated answer with the output. — Syam S, Jul 16 '14 at 17:23
Awesom, it seems to work, I will try to duplicate to my program ! — Thomas Th., Jul 17 '14 at 14:35

Sort a LinkedHashMap with Values and with Time Priority in case of Equal

1 Answers1