Ouput is not expected in sorting coin array values using selection sorting

Question

I want to sort a Coin array according to their values by using Selection sort but the output is not showing properly. The output display as some other unique format. I have tried to resolve the problem but still unable to find the solution. I have two classes CoinSelectionSorter and a Coin class. I am using Comparable interface to sort the Coin values. The entire code is like that-

CoinSelectionSorter.java:

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
       This class sorts an array of coins, using the selection sort
       algorithm.
 */
public class CoinSelectionSorter {
    public static void main (String args[])
    {
        //public void sort() {

        Coin[] list =  new Coin[] {new Coin(2, "Johan"),new Coin(5, "peter"), new Coin(1, "robin"),new Coin(15, "walker") }; // example data;

        List <Coin> p = Arrays.asList(list);
        Collections.sort(p);
        System.out.println(p);  
        list = p.toArray(list); 
        System.out.println(p);
    }
}

Coin.java:

public class Coin implements Comparable<Coin >{

    Integer r;
    String p;

    public Coin(Integer r, String p) {
        // TODO Auto-generated constructor stub
        this.r = r;
        this.p = p;
    }

    @Override
    public int compareTo(Coin test) {
        // TODO Auto-generated method stub
        return this.r - test.r;
    }
}

It gives output like:

[Coin@19821f, Coin@addbf1, Coin@42e816, Coin@9304b1]
[Coin@19821f, Coin@addbf1, Coin@42e816, Coin@9304b1]

But I expect output as:

[2, Johan], [5, 'peter], [1, robin], [15, walker]
[1, robin], [2, Johan], [5, 'peter], [15, walker]

Kindly help to resolve this issue. Thanks in advance.

Answer 1

All you need to is override the default toString() in coin to generate the output string in desired format. Like:

@Override
public String toString() {
    return "[" + r + ", " + p + "]";
}

Additionally, to get the output you mentioned, you need to print the list of coins before sorting in CoinSelectionSorter.

Answer 2

You need to implement toString() in your class Coin:

@Override
public String toString() {
    return "Coin [r=" + r + ", p=" + p + "]";
}

This code has been generated with Eclipse. You can easily do that in Source > Generate toString()...