Added kNearestNeighbour and refactored Vector to a package level above and added a constructor

test/machine_learning/nearest_neighbour/KNearestNeighbourTest.java

@@ -0,0 +1,62 @@
+package machine_learning.nearest_neighbour;
+
+import machine_learning.Vector;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class KNearestNeighbourTest
+{
+    List<Vector> positives;
+    List<Vector> negatives;
+
+    @BeforeAll
+    void initLearnData()
+    {
+        this.positives = new ArrayList<>(List.of(
+                new Vector(8d, 4d),
+                new Vector(8d, 6d),
+                new Vector(9d, 2d),
+                new Vector(9d, 5d))
+        );
+
+        this.negatives = new ArrayList<>(List.of(
+                new Vector(6d, 1d),
+                new Vector(7d, 3d),
+                new Vector(8d, 2d),
+                new Vector(9d, 0d))
+        );
+    }
+
+    @Test
+    public void shouldReturnCorrectClassForVectorWithKEquals3()
+    {
+        var kNearestNeighbour = new KNearestNeighbour((a ,b) -> Math.abs(a.get(0) - b.get(0)) + Math.abs(a.get(1) - b.get(1)), 3);
+        var vector = new Vector(8, 3.5);
+
+        var actualClass = kNearestNeighbour.kNearestNeighbour(this.positives, this.negatives, vector);
+        var expectedClass = DataClass.NEGATIVE;
+
+        assertEquals(expectedClass, actualClass);
+    }
+
+    @Test
+    public void shouldReturnCorrectClassForVectorWithKEquals5()
+    {
+        var kNearestNeighbour = new KNearestNeighbour((a ,b) -> Math.abs(a.get(0) - b.get(0)) + Math.abs(a.get(1) - b.get(1)), 5);
+        var vector = new Vector(8, 3.5);
+
+        var actualClass = kNearestNeighbour.kNearestNeighbour(this.positives, this.negatives, vector);
+        var expectedClass = DataClass.POSITIVE;
+
+        assertEquals(expectedClass, actualClass);
+    }
+}