CustomCompare

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

class Animals implements Comparable<Animals>{
    private String vrsta;
    public Animals(String vrsta) {
        this.vrsta = vrsta;
    }
    public String getVrsta() {
        return vrsta;
    }
    public void setVrsta(String vrsta) {
        this.vrsta = vrsta;
    }
    @Override
    public String toString() {
        return "vrsta";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((vrsta == null) ? 0 : vrsta.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Animals other = (Animals) obj;
        if (vrsta == null) {
            if (other.vrsta != null)
                return false;
        } else if (!vrsta.equals(other.vrsta))
            return false;
        return true;
    }
     public int compareTo(Animals person){
        return person.vrsta.compareTo(vrsta);
     }

}


public class CustomCompares {
    public static void main(String[] args) {
        List<Animals> lista= new ArrayList<Animals>();
        Set<Animals> set = new TreeSet<Animals>();


        addItems(lista);
        addItems(set);
        Collections.sort(lista);
        printItems(lista);
        System.out.println();
        printItems(set);
    }

    private static void addItems(Collection<Animals> col) {
        col.add(new Animals("predrag"));
        col.add(new Animals("zoran"));
        col.add(new Animals("goran"));
        col.add(new Animals("dzon"));

    }

    private static void printItems (Collection<Animals> col) {
        for(Animals elementi: col){
            System.out.println(elementi.getVrsta());
        }

    }
}