Java TreeMap Comparable vs Comparator, can someone share practical example how to use it?

Here is practical example with TreeMap and Comparable vs Comparator:

import org.junit.Test;

import java.util.Comparator;
import java.util.TreeMap;

import static org.assertj.core.api.Assertions.assertThat;

public class ComparableVsComparatorExample {

    @Test
    public void test() {
        {
            // Point1 implements Comparable<Point1>
            TreeMap<Point1, String> map1 = new TreeMap<>();
            map1.put(new Point1(1, 2), "pt1");
            map1.put(new Point1(1, 2), "pt1-override"); // override value for key: Point(1, 2)
            map1.put(new Point1(2, 1), "pt2");

            assertThat(map1).hasSize(2);
            assertThat(map1.get(new Point1(1, 2))).isEqualTo("pt1-override");
            assertThat(map1.get(new Point1(2, 1))).isEqualTo("pt2");
            assertThat(map1.toString())
                    .isEqualTo("{Point{x=1, y=2}=pt1-override, Point{x=2, y=1}=pt2}");
        }
        {
            // Point2 doesn't implement Comparable,
            // but we pass Comparator<Point2> implementation via TreeMap constructor
            TreeMap<Point2, String> map2 = new TreeMap<>(new Comparator<Point2>() {
                @Override
                public int compare(Point2 o1, Point2 o2) {
                    // asc order
                    int compareX = Integer.compare(o1.getX(), o2.getX());
                    if (compareX == 0) { // eq
                        return Integer.compare(o1.getY(), o2.getY());
                    }
                    return compareX; // -1 or 1 - if o1X < o2X ret -1, if o1X > o2X ret 1
                }
            });
            map2.put(new Point2(1, 2), "pt1");
            map2.put(new Point2(1, 2), "pt1-override"); // override value for key: Point(1, 2)
            map2.put(new Point2(2, 1), "pt2");
    
            assertThat(map2).hasSize(2);
            assertThat(map2.get(new Point2(1, 2))).isEqualTo("pt1-override");
            assertThat(map2.get(new Point2(2, 1))).isEqualTo("pt2");
            assertThat(map2.toString())
                    .isEqualTo("{Point{x=1, y=2}=pt1-override, Point{x=2, y=1}=pt2}");
        }
    }
    
    private static class Point1 implements Comparable<Point1> {
        private final int x;
        private final int y;
        public Point1(int x, int y) {this.x = x;this.y = y;}
        public int getX() {return x;}
        public int getY() {return y;}
        @Override
        public String toString() {return "Point{" + "x=" + x + ", y=" + y + '}';}

        @Override
        public int compareTo(Point1 o2) {
            // asc order
            Point1 o1 = this;
            int compareX = Integer.compare(o1.getX(), o2.getX());
            if (compareX == 0) { // eq
                return Integer.compare(o1.getY(), o2.getY());
            }
            return compareX; // -1 or 1 - if o1X < o2X ret -1, if o1X > o2X ret 1
        }
    }

    private static class Point2 {
        private final int x;
        private final int y;
        public Point2(int x, int y) {this.x = x;this.y = y;}
        public int getX() {return x;}
        public int getY() {return y;}
        @Override
        public String toString() {return "Point{" + "x=" + x + ", y=" + y + '}';}
    }
}