Comparator sort issue

[Jack Bento]

Hi there

Please can you let me know where I went wrong with my sort method?

Thanks in advance!

import java.util.*;

class Jolie2{  
	int j;
	String s;
	
	Jolie2(int j, String s){
		this.j = j;
		this.s = s;
	}
}

class Draft implements Comparator<String> {
	public int compare(String a, String b) { 
		return b.compareTo(a); 
	}
}

public class Pitt2{
	public static void main(String [] args){
		List <Jolie2>l = new ArrayList<Jolie2>();
		l.add(new Jolie2(4, "Prue"));
		l.add(new Jolie2(7878, "Keith"));
		l.add(new Jolie2(7, "Tyke"));
		l.add(new Jolie2(49, "Clive"));
		l.add(new Jolie2(112, "Kenneth"));
		
		Collections.sort(l, new Draft());
		
		for (Jolie2 t : l)
			System.out.println(t.s);
	}
}

[Sebastian Janisch]

It should throw a big fat exception ...

Your comparator expects two Strings but what it gets is two Jolies.
What exactly is it that you want to compare ??

What you need to do is parameterize Draft with Jolie2 and then compare the necessary values.

[Jack Bento]

Sebastian you are a genius

I changed draft to:

class Draft implements Comparator<Jolie2> {
	public int compare(Jolie2 a, Jolie2 b) { 
		return a.getS().compareTo(b.s); 
	}
}

[Sebastian Janisch]

sure

why are you using a getter for a but direct access for b ??? and why are your instance variables not private ?

[Wouter Oet]

Or you could use the comparable interface

import java.util.*;   
  
class Jolie2 implements Comparable<Jolie2>{     
    int j;   
    String s;   
       
    Jolie2(int j, String s){   
        this.j = j;   
        this.s = s;   
    }
    
    public int compareTo(Jolie2 j)
    {
    	return s.compareTo(j.s);
    }
}   
  
public class Pitt2{   
    public static void main(String [] args){   
        List <Jolie2>l = new ArrayList<Jolie2>();   
        l.add(new Jolie2(4, "Prue"));   
        l.add(new Jolie2(7878, "Keith"));   
        l.add(new Jolie2(7, "Tyke"));   
        l.add(new Jolie2(49, "Clive"));   
        l.add(new Jolie2(112, "Kenneth"));   
           
        Collections.sort(l);   
           
        for (Jolie2 t : l)   
            System.out.println(t.s);   
    }   
}      

[Jack Bento]

Sebastian Janisch wrote:sure

why are you using a getter for a but direct access for b ??? and why are your instance variables not private ?

I was just trying to get the comparator working. You're right, mustn't get into bad habits.

[Sebastian Janisch]

good boy :-)

[Jack Bento]

Thanks Wouter. I got the comparable going earlier