CODEWITHSUNDEEP
javasortingcollectionsarraylist
Adrian Modliszewski
Adrian Modliszewski

Reputation: 1124

Java Custom ArrayList Object Sorting

I have a problem with sorting an ArrayList of my own objects.

My class of these objects looks like that:

public class Robal {
    int[] gen = new int[5];
    int fit;
    Random losuj = new Random();

    public Robal(int przelacz) {
        for (int i=0; i<5; i++ ) {
            gen[i]=losuj.nextInt(2);
        }
        fit=dopasuj(gen, przelacz);    
    }

    int dopasuj(int[] gen, int przelacz)    {
        int toDec=(gen[0]*1)+(gen[1]*2)+(gen[2]*4)+(gen[3]*8)+(gen[4]*16);
        return y(toDec, przelacz);
    }

    int y(int toDec, int przelacz) {
        if (przelacz == 1) {
            return toDec*toDec;
        } else if (przelacz == 2) {
            return 1;
        } else if(przelacz == 3) {
            return 1;
        } else if(przelacz == 4) {
            return 1;
        } else {
            return 1;
        }
    }

    void drukuj(int i) {
        System.out.println("Geny Robala "+i+": "+gen[0]+" "+gen[1]+" "+gen[2]+" "+gen[3]+" "+gen[4]+"\tfit:"+fit);
    }
}

and My Main class is:

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

public class PE {

public static void main (String[] args){
ArrayList<Robal> Robale = new ArrayList<Robal>();
int i=0;
while(i!=5){
Robale.add(new Robal(1));
i++;
}
Robale.get(0).drukuj(1);
Robale.get(1).drukuj(2);
Robale.get(2).drukuj(3);
Robale.get(3).drukuj(4);

Collections.sort(Robale, new Comparator<Robal>() {
public int compare(Robal a, Robal b){
return a.fit - b.fit;
}
});

Robale.get(0).drukuj(1);
Robale.get(1).drukuj(2);
Robale.get(2).drukuj(3);
Robale.get(3).drukuj(4);


}


}

but most of the time the Data before and after sorting is not the same... example result:

Geny Robala 1: 0 1 1 0 0 fit:36
Geny Robala 2: 1 0 1 0 1 fit:441
Geny Robala 3: 1 1 0 0 1 fit:361
Geny Robala 4: 0 1 1 1 0 fit:196
Geny Robala 1: 0 1 1 0 0 fit:36
Geny Robala 2: 0 0 0 1 0 fit:64
Geny Robala 3: 0 1 1 1 0 fit:196
Geny Robala 4: 1 1 0 0 1 fit:361

Upvotes: 0

Views: 319

Answers (2)

Ashwinee K Jha
Ashwinee K Jha

Reputation: 9307

You are adding 5 items to the array and printing only 4 before and after sorting. It seems that 5th item in unsorted list made it to the top 4. Can you print one more item and see if things look good?

Upvotes: 1

Slash
Slash

Reputation: 506

Are you sure you are not instantiating new Robal while sorting the list? that would cause the random values to shift

Upvotes: 1

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