Sorting question !!!

[alrebatsd]

Hello,

I have a question about sorting.

How can I sort HashMap by element in the HashMap ?
That's meaning, if I have in the Sys class map such as:

protected Map <Constructors,RaceTeam>raceTeam=new HashMap<Constructors,RaceTeam>();

and in the RaceTeam class I have this variables:

	protected Constructors name;
	protected int totalScore;
	protected URL website;
	protected double budget;
	protected Race lastRace;

and I want to sort the the eaceTeam map by the "totalScore" from the biggest to the smallest, How can I do this thing ?

I do the follwing:

TreeMap<Integer,RaceTeam> teams = new TreeMap<Constructors,RaceTeam> teams = new TreeMap<Constructors,RaceTeam>();		
		Iterator iter = teams.keySet().iterator();
	    Object obj;
	    
	    while (iter.hasNext()) {
		      obj = iter.next();
		      System.out.println(teams.get(obj).getName() + " " + teams.get(obj).getTotalScore());
		    }

The out put will be:
Brawn 390
Toyota 584
BMW_Sauber 470
Renault 782
Toro_Rosso 488
Force_India 0
Ferrari 1049

I want it to be:
Ferrari 1049
Renault 782
Toyota 584
Toro_Rosso 488
BMW_Sauber 470
Brawn 390
Force_India 0

[Singing Boyo]

Design your own comparator or make your RaceTeam class implement comparable
e.g.

public class RaceTeam implements Comparable<RaceTeam>{
     public int compareTo(RaceTeam anotherTeam){
          return ((getTotalScore()-anotherTeam.getTotalScore())*(-1));
     }//this should do what you want...
}//below is a more readable method... also this one could be faulty

//more reliable
public class RaceTeam implements Comparable<RaceTeam>{
     public int compareTo(RaceTeam anotherTeam){
          if(getTotalScore()==anotherTeam.getTotalScore())
               return 0;
          else if(getTotalScore()>anotherTeam.getTotalScore())
               return 1;
          else return 0;
     }//this will do what you want
}//probably more readable than above, and has no possibility of error

compareTo methods in Comparator<T>/Comparable<T> return -x if the object the method is being called on is 'less than' the parameter, 0 if the parameter is 'equal to' the object, and x if the object is 'greater than' the parameter.

Simply, negative for less than, 0 for equals, and positive for greater than.

Hopefully this helps,
Singing Boyo

EDIT: You probably don't want to sort whatever Map you are using. Instead, transfer whatever needs sorting into an ArrayList or some other storage facility with a sort method, and sort that. Maps are just that... maps. They shouldn't be ordered if it is at all avoidable.

[Fubarable]

EDIT: You probably don't want to sort whatever Map you are using. Instead, transfer whatever needs sorting into an ArrayList or some other storage facility with a sort method, and sort that. Maps are just that... maps. They shouldn't be ordered if it is at all avoidable.

Unless you use a sortable Map such as a TreeMap; then it's a Map that... sorts!

[alrebatsd]

Hello'
Thank you, but In the HomwWork I cannot use the Collection sort.

in another side I do the compareTo, but I didn't know how can I use the compare to for comparing !!

Should i iterate on the map ?
Anyone can giving me an example how to use the the compareTo() ?

thank you :)

[alrebatsd]

Hello,

I do the method like this:

public void printRaceTeamsRankedReport(){
		TreeMap<Constructors,RaceTeam> teams = new TreeMap<Constructors,RaceTeam>();
		teams.putAll( raceTeam);
		TreeMap <Integer,Constructors> teamCo = new TreeMap <Integer,Constructors>();
		

		Object obj;
	    Iterator itera = teams.keySet().iterator();
	    while ((itera.hasNext())) {

	    	obj = itera.next();
	    	teamCo.put(teams.get(obj).getTotalScore(), teams.get(obj).getName());
		    }
	    
	    MyFileLogWriter.writeToFileInSeparateLine("\n====Race Teams Ranked Report====");
	    
	    Iterator it = teams.keySet().iterator();
//	    Object obj;
	    
	    MyFileLogWriter.writeToFileInSeparateLine(teamCo.descendingMap());
	    
	    MyFileLogWriter.writeToFileInSeparateLine("====End of Race Teams Ranked Report====\n");		
		
	}

The out put is:
{1049=Ferrari, 782=Renault, 584=Toyota, 488=Toro_Rosso, 470=BMW_Sauber, 390=Brawn, 0=Force_India}


How can get it like this :

Ferrari 1049
Renault 782
Toyota 584
Toro_Rosso 488
BMW_Sauber 470
Brawn 390
Force_India 0

[alrebatsd]

Thank you brothers,

I do the method :)
I did loop thru the map

Thank u ,