Add hashcode and equals methods to LatLong (#179)

* Add hashcode and equals methods to LatLong

Discovered that LatLong doesn't actually implement hashcode() or
equals(), so we can't actually put it into a Set<> or call distinct() on
it in a stream.

Used IntelliJ IDEA's automatic generation of these things. Happy to
change the implementation if desired.

* Performance fix

Objects.hashCode() under the hood creates a bunch of objects we don't
need, so directly create and aggregate the hashcodes.

geo/src/main/java/com/github/davidmoten/geo/LatLong.java

@@ -61,4 +61,21 @@ public String toString() {
         return builder.toString();
     }
 
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        final LatLong latLong = (LatLong) o;
+        return Double.compare(lat, latLong.lat) == 0 && Double.compare(lon, latLong.lon) == 0;
+    }
+
+    @Override
+    public int hashCode() {
+        return 31 * Double.hashCode(lat) + Double.hashCode(lon);
+    }
+
 }

geo/src/test/java/com/github/davidmoten/geo/LatLongTest.java

@@ -1,9 +1,9 @@
 package com.github.davidmoten.geo;
 
-import static org.junit.Assert.assertEquals;
-
 import org.junit.Test;
 
+import static org.junit.Assert.assertEquals;
+
 /**
  * Unit tests for {@link LatLong}.
  * 
@@ -18,4 +18,15 @@ public void testToString() {
                 new LatLong(10, 20).toString());
     }
 
+    @Test
+    public void testHashCode() {
+        float lat = 20.05f;
+        float lon = -15.5f;
+        LatLong a = new LatLong(lat, lon);
+        LatLong b = new LatLong(lat, lon);
+
+        assertEquals(a.hashCode(), b.hashCode());
+        assertEquals(a, b);
+    }
+
 }