Java Comparator class to sort particular object array

Question

I have a float array and a String array. each float value match with a specific String. I would like to sort the float array keeping the own string using :

public static <T> void sort(T[] a,Comparator<? super T> c)

Here is the code:

public class ResultVoiceObject
{

     private  String frase;
     private float ranking;
     public ResultVoiceObject(String f, float r) 
       {
        this.frase=f;
        this.ranking= r;
       }  
     }
     public class VoiceRecognitionDemo extends Activity
     {

       // Populate the wordsList with the String values the recognition engine thought it heard
        ArrayList<String> matches = data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);          
        //il Ranking
        float[] score= data.getFloatArrayExtra(RecognizerIntent.EXTRA_CONFIDENCE_SCORES);

        ResultVoiceObject[] risultati= new ResultVoiceObject[score.length];
        for (i=0; i<risultati.length;i++)
        {       
            risultati[i]=new ResultVoiceObject(matches.get(i), score[i]);       
        }          
        ResultVoiceObject[] risultatiDaOrdinare= risultati;  // risultati contais ResultVoiceObject elements
                    /*sorting*/
        }

How can I sort by ranking and keeping the own String?

Thanks a lot.

please show us the code you tried to solve this problem with — Marco Forberg
– Marco Forberg, Commented Jun 18, 2013 at 8:34
I don't have code, I don't know how to use Arrays.sort with object like mine. I solved in another way but my manager would likes I use Array.sort(result, Comparator). Can I? — alfo888_ibg
– alfo888_ibg, Commented Jun 18, 2013 at 8:36
you need to create your own comparator, for example ResultVoiceObjectComparator — sotix
– sotix, Commented Jun 18, 2013 at 8:37

gma · Accepted Answer · 2013-06-18 08:41:09Z

7

ResultVoiceObject[] objects = ...
Arrays.sort(objects, new Comparator<ResultVoiceObject>() {

    @Override
    public int compare(ResultVoiceObject arg0, ResultVoiceObject arg1) {
        return Float.compare(arg0.getRanking(), arg1.getRanking());
    }

});

answered Jun 18, 2013 at 8:41

gma

2,56317 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

alfo888_ibg Over a year ago

error: Multiple markers at this line - Comparator cannot be resolved to a type - The method sort(T[], Comparator<? super T>) in the type Arrays is not applicable for the arguments (ResultVoiceObject[], new Comparator<ResultVoiceObject>(){})

gma Over a year ago

import java.util.Arrays; import java.util.Comparator;

alfo888_ibg Over a year ago

yes it's true! So I deleted the implements and compare methos! I voted you thanks!

alfo888_ibg Over a year ago

I posted a complete solution!

c.P.u1 · Accepted Answer · 2013-06-18 08:47:11Z

3

Assuming you have a getRanking() accessor for the private field ranking.

public class ResultComparator implements Comparator<ResultVoiceObject> {
  public int compare(ResultVoiceObject r1, ResultVoiceObject r2) {
    float f1 = r1.getRanking();
    float f2 = r2.getRanking();
    if(f1 > f2) return 1;
    else if(f1 < f2) return -1;
    return 0;
  }

}

Arrays.sort(resultsArray, new ResultComparator());

edited Jun 18, 2013 at 8:47

answered Jun 18, 2013 at 8:37

c.P.u1

17.1k6 gold badges48 silver badges42 bronze badges

4 Comments

Grzegorz Żur Over a year ago

Watch out! Implementing comparator by using arithmetic operations can result in wrong sort order because of overflow.

gma Over a year ago

(int)r1.getRanking() - (int)r2.getRanking(); meaning that i.e. 7.1 == 7.2?

c.P.u1 Over a year ago

@gma, I was in the process of editing my post. Sorry for that.

alfo888_ibg Over a year ago

thanks i solved with another solution, you can see on my post

Prasad Kharkar · Accepted Answer · 2013-06-18 09:04:35Z

You need to implement the Comparator interface. You can create multiple sort sequences while using Comparator.

Suppose you want to sort your array according to your ranking, then create a separate class which implements Comparator

public Class RankingSorter implements Comparator<ResultVoiceObject> {
   public int compare(ResultVoiceObject one, ResultVoiceObject another){
       return (int)(one.getRanking() - another.getRanking());
   }
}

Then in the new class that you want to sort your array, You create the object of the comparator and pass it to collection

RankingSorter rs = new RankingSorter();
Collections.sort(yourArray, rs);

This is the overloaded version of sort method which takes the comparator.

I had written a full tutorial regarding this a while ago http://www.dreamincode.net/forums/topic/174322-the-comparable-and-comparator-interface-part-ii/

Here is the ResultVoicObject class

package com.compare;

public class ResultVoiceObject {

private String frase;
private float ranking;

public ResultVoiceObject(String f, float r) {
    this.frase = f;
    this.ranking = r;
}

public String getFrase() {
    return frase;
}

public void setFrase(String frase) {
    this.frase = frase;
}

public float getRanking() {
    return ranking;
}

public void setRanking(float ranking) {
    this.ranking = ranking;
}

@Override
public String toString() {
    return "ResultVoiceObject [frase=" + frase + ", ranking=" + ranking
            + "]";
}

}

Implement the Comparator interface as follows, you need to implement compare method

 package com.compare;

 import java.util.Comparator;

  public class RankingSort implements Comparator<ResultVoiceObject> {

public int compare(ResultVoiceObject one, ResultVoiceObject another){
    return (int) (one.getRanking() - another.getRanking());
}
  }

You can test it as below.

 package com.compare;

 import java.util.ArrayList;
 import java.util.Collections;

 public class RankingSorterTest{

public static void main(String [] args){

    ArrayList<ResultVoiceObject> list = new ArrayList<ResultVoiceObject>();
    list.add(new ResultVoiceObject("one", 1));
    list.add(new ResultVoiceObject("five", 5));
    list.add(new ResultVoiceObject("three", 3));

    Collections.sort(list,new RankingSort());
    System.out.println(list);

}
  }

If you want to create a sorting sequence using frase, then you just need to create a new comparator class for it and sort just as I have sorted above

Hope this helps... took a lot of efforts from me also :D :D

alfo888_ibg · Accepted Answer · 2013-06-18 09:21:01Z

I solved merging both answare:

public class VoiceRecognitionDemo extends Activity implements Comparator<ResultVoiceObject {

protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
        ...
        ResultVoiceObject[] risultati= ...;     
        Arrays.sort(risultati, new Comparator<ResultVoiceObject>() {
            @Override
            public int compare(ResultVoiceObject arg0, ResultVoiceObject arg1) {
                return Float.compare(arg0.getRanking(), arg1.getRanking());
            }
        });  

    }


public int compare(ResultVoiceObject lhs, ResultVoiceObject rhs) {
    // TODO Auto-generated method stub
    return 0;
}

}

Where:

 public class ResultVoiceObject
 {

 private  String frase;
 private float ranking;
 public ResultVoiceObject(String f, float r) 
   {
    this.frase=f;
    this.ranking= r;
   }  
 }

Another way is:

ADD

import java.util.Arrays;

import java.util.Comparator;

REMOVE: implements Comparator and the compare methos out onActivityResult

Thanks stackoverflow comunity!

Collectives™ on Stack Overflow

Java Comparator class to sort particular object array

4 Answers 4

4 Comments

4 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

4 Comments

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related