ArrayList + Comparator

CompList.java

package lesson7.CompList;

import java.util.Comparator;

public class CompList implements Comparator {

    @Override
    public int compare(Object o1, Object o2) {

        String oStr1 = (String) o1;
        String oStr2 = (String) o2;

        if (oStr1.compareTo(oStr2) > 0) {
            return -1;
        } else if (oStr1.compareTo(oStr2) > 0) {
            return 1;
        } else return 0;
    }
}

Launcher.java

package lesson7.CompList;

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

public class Launcher {

    public static void main(String[] args) {

        ArrayList<String> arr = new ArrayList<String>();
        CompList cl = new CompList();

        arr.add("kolya");
        arr.add("yulya");
        arr.add("valya");
        arr.add("zoya");
        arr.add("lilya");
        arr.add("petr");
        arr.add("kirill");
        arr.add("kotya");
        arr.add("alya");
        arr.add("sasha");

        System.out.println(Arrays.toString(arr.toArray()));
        Collections.sort(arr, cl);
        System.out.println(Arrays.toString(arr.toArray()));
    }
}