Use List rather than array, accept super type in extractor

jazdw · jazdw · commit b3479d955181 · 2025-03-12T11:18:35.000-06:00
diff --git a/src/main/java/com/goebl/simplify/AbstractSimplify.java b/src/main/java/com/goebl/simplify/AbstractSimplify.java
@@ -12,10 +12,7 @@
  */
 abstract class AbstractSimplify<T> {
 
-    private T[] sampleArray;
-
-    protected AbstractSimplify(T[] sampleArray) {
-        this.sampleArray = sampleArray;
+    protected AbstractSimplify() {
     }
 
     /**
@@ -27,12 +24,15 @@ protected AbstractSimplify(T[] sampleArray) {
      *                       applying Douglas-Peucker (should be a bit faster)
      * @return simplified list of points
      */
-    public T[] simplify(T[] points,
+    public List<T> simplify(List<T> points,
                         double tolerance,
                         boolean highestQuality) {
 
-        if (points == null || points.length <= 2) {
-            return points;
+        if (points == null) {
+            throw new IllegalArgumentException();
+        }
+        if (points.size() <= 2) {
+            return new ArrayList<>(points);
         }
 
         double sqTolerance = tolerance * tolerance;
@@ -46,15 +46,15 @@ public T[] simplify(T[] points,
         return points;
     }
 
-    T[] simplifyRadialDistance(T[] points, double sqTolerance) {
+    List<T> simplifyRadialDistance(List<T> points, double sqTolerance) {
         T point = null;
-        T prevPoint = points[0];
+        T prevPoint = points.get(0);
 
-        List<T> newPoints = new ArrayList<T>();
+        List<T> newPoints = new ArrayList<>();
         newPoints.add(prevPoint);
 
-        for (int i = 1; i < points.length; ++i) {
-            point = points[i];
+        for (int i = 1; i < points.size(); ++i) {
+            point = points.get(i);
 
             if (getSquareDistance(point, prevPoint) > sqTolerance) {
                 newPoints.add(point);
@@ -66,7 +66,7 @@ T[] simplifyRadialDistance(T[] points, double sqTolerance) {
             newPoints.add(point);
         }
 
-        return newPoints.toArray(sampleArray);
+        return newPoints;
     }
 
     private static class Range {
@@ -79,14 +79,14 @@ private Range(int first, int last) {
         int last;
     }
 
-    T[] simplifyDouglasPeucker(T[] points, double sqTolerance) {
+    List<T> simplifyDouglasPeucker(List<T> points, double sqTolerance) {
 
-        BitSet bitSet = new BitSet(points.length);
+        BitSet bitSet = new BitSet(points.size());
         bitSet.set(0);
-        bitSet.set(points.length - 1);
+        bitSet.set(points.size() - 1);
 
-        List<Range> stack = new ArrayList<Range>();
-        stack.add(new Range(0, points.length - 1));
+        List<Range> stack = new ArrayList<>();
+        stack.add(new Range(0, points.size() - 1));
 
         while (!stack.isEmpty()) {
             Range range = stack.remove(stack.size() - 1);
@@ -96,7 +96,7 @@ T[] simplifyDouglasPeucker(T[] points, double sqTolerance) {
 
             // find index of point with maximum square distance from first and last point
             for (int i = range.first + 1; i < range.last; ++i) {
-                double sqDist = getSquareSegmentDistance(points[i], points[range.first], points[range.last]);
+                double sqDist = getSquareSegmentDistance(points.get(i), points.get(range.first), points.get(range.last));
 
                 if (sqDist > maxSqDist) {
                     index = i;
@@ -112,12 +112,12 @@ T[] simplifyDouglasPeucker(T[] points, double sqTolerance) {
             }
         }
 
-        List<T> newPoints = new ArrayList<T>(bitSet.cardinality());
+        List<T> newPoints = new ArrayList<>(bitSet.cardinality());
         for (int index = bitSet.nextSetBit(0); index >= 0; index = bitSet.nextSetBit(index + 1)) {
-            newPoints.add(points[index]);
+            newPoints.add(points.get(index));
         }
 
-        return newPoints.toArray(sampleArray);
+        return newPoints;
     }
 
 
diff --git a/src/main/java/com/goebl/simplify/Simplify.java b/src/main/java/com/goebl/simplify/Simplify.java
@@ -8,20 +8,19 @@
  */
 public class Simplify<T> extends AbstractSimplify<T> {
 
-    private final PointExtractor<T> pointExtractor;
+    private final PointExtractor<? super T> pointExtractor;
 
     /**
      * Simple constructor for 2D-Simplifier.
      * <br>
      * With this simple constructor your array elements must implement {@link Point}.<br>
      * If you have coordinate classes which cannot be changed to implement <code>Point</code>, use
-     * {@link #Simplify(Object[], PointExtractor)} constructor!
+     * {@link #Simplify(PointExtractor)} constructor!
      *
-     * @param sampleArray pass just an empty array (<code>new MyPoint[0]</code>) - necessary for type consistency.
      */
-    public Simplify(T[] sampleArray) {
-        super(sampleArray);
-        this.pointExtractor = new PointExtractor<T>() {
+    public Simplify() {
+        super();
+        this.pointExtractor = new PointExtractor<>() {
             @Override
             public double getX(T point) {
                 return ((Point) point).getX();
@@ -40,11 +39,10 @@ public double getY(T point) {
      * With this constructor your array elements do not have to implement a special interface like {@link Point}.<br>
      * Implement a {@link PointExtractor} to give <code>Simplify</code> access to your coordinates.
      *
-     * @param sampleArray pass just an empty array (<code>new MyPoint[0]</code>) - necessary for type consistency.
      * @param pointExtractor your implementation to extract X and Y coordinates from you array elements.
      */
-    public Simplify(T[] sampleArray, PointExtractor<T> pointExtractor) {
-        super(sampleArray);
+    public Simplify(PointExtractor<? super T> pointExtractor) {
+        super();
         this.pointExtractor = pointExtractor;
     }
 
diff --git a/src/main/java/com/goebl/simplify/Simplify3D.java b/src/main/java/com/goebl/simplify/Simplify3D.java
@@ -8,20 +8,18 @@
  */
 public class Simplify3D<T> extends AbstractSimplify<T> {
 
-    private final Point3DExtractor<T> pointExtractor;
+    private final Point3DExtractor<? super T> pointExtractor;
 
     /**
      * Simple constructor for 3D-Simplifier.
      * <br>
      * With this simple constructor your array elements must implement {@link Point3D}.<br>
      * If you have coordinate classes which cannot be changed to implement <code>Point3D</code>, use
-     * {@link #Simplify3D(Object[], Point3DExtractor)} constructor!
-     *
-     * @param sampleArray pass just an empty array (<code>new MyPoint[0]</code>) - necessary for type consistency.
+     * {@link #Simplify3D(Point3DExtractor)} constructor!
      */
-    public Simplify3D(T[] sampleArray) {
-        super(sampleArray);
-        this.pointExtractor = new Point3DExtractor<T>() {
+    public Simplify3D() {
+        super();
+        this.pointExtractor = new Point3DExtractor<>() {
             @Override
             public double getX(T point) {
                 return ((Point) point).getX();
@@ -45,11 +43,10 @@ public double getZ(T point) {
      * With this constructor your array elements do not have to implement a special interface like {@link Point3D}.<br>
      * Implement a {@link Point3DExtractor} to give <code>Simplify3D</code> access to your coordinates.
      *
-     * @param sampleArray pass just an empty array (<code>new MyPoint[0]</code>) - necessary for type consistency.
      * @param pointExtractor your implementation to extract X, Y and Z coordinates from you array elements.
      */
-    public Simplify3D(T[] sampleArray, Point3DExtractor<T> pointExtractor) {
-        super(sampleArray);
+    public Simplify3D(Point3DExtractor<? super T> pointExtractor) {
+        super();
         this.pointExtractor = pointExtractor;
     }
 
diff --git a/src/test/java/com/goebl/simplify/GpsLocationTest.java b/src/test/java/com/goebl/simplify/GpsLocationTest.java
@@ -11,7 +11,7 @@
  * Test class for {@link Simplify} in context of typical Gps-Tracks.
  * <br>
  * This is more of a demonstration than a test.
- * See http://stackoverflow.com/q/34010298/2176962
+ * See <a href="http://stackoverflow.com/q/34010298/2176962">http://stackoverflow.com/q/34010298/2176962</a>
  *
  * @author goebl
  * @since 01.12.15
@@ -36,9 +36,9 @@ public double getLng() {
         }
     }
 
-    private static LatLng[] coords;
+    private static List<LatLng> coords;
 
-    private static PointExtractor<LatLng> latLngPointExtractor = new PointExtractor<LatLng>() {
+    private static final PointExtractor<LatLng> latLngPointExtractor = new PointExtractor<>() {
         @Override
         public double getX(LatLng point) {
             return point.getLat() * 1000000;
@@ -53,25 +53,25 @@ public double getY(LatLng point) {
     @BeforeClass
     public static void readPoints() throws Exception {
         Point[] allPoints = SimplifyTest.readPoints("gps-track.txt");
-        List<LatLng> coordsList = new ArrayList<LatLng>(allPoints.length);
+        List<LatLng> coordsList = new ArrayList<>(allPoints.length);
 
         for (Point point:allPoints) {
             coordsList.add(new LatLng(point.getX(), point.getY()));
         }
-        coords = coordsList.toArray(new LatLng[coordsList.size()]);
+        coords = coordsList;
     }
 
     @Test
-    public void testSimplifyGpsTrack() throws Exception {
-        Simplify<LatLng> simplify = new Simplify<LatLng>(new LatLng[0], latLngPointExtractor);
+    public void testSimplifyGpsTrack() {
+        Simplify<LatLng> simplify = new Simplify<>(latLngPointExtractor);
 
-        LatLng[] simplified = simplify.simplify(coords, 20f, false);
-        System.out.println("coords:" + coords.length + " simplified:" + simplified.length);
-        Assert.assertTrue("should be simplified to less than 33%", simplified.length < (coords.length / 3));
+        List<LatLng> simplified = simplify.simplify(coords, 20f, false);
+        System.out.println("coords:" + coords.size() + " simplified:" + simplified.size());
+        Assert.assertTrue("should be simplified to less than 33%", simplified.size() < (coords.size() / 3));
 
         simplified = simplify.simplify(coords, 50f, true);
-        System.out.println("coords:" + coords.length + " simplified:" + simplified.length);
-        Assert.assertTrue("should be simplified to less than 20%", simplified.length < (coords.length * 0.2));
+        System.out.println("coords:" + coords.size() + " simplified:" + simplified.size());
+        Assert.assertTrue("should be simplified to less than 20%", simplified.size() < (coords.size() * 0.2));
     }
 
 }
diff --git a/src/test/java/com/goebl/simplify/Simplify3DTest.java b/src/test/java/com/goebl/simplify/Simplify3DTest.java
@@ -3,6 +3,10 @@
 import org.junit.Assert;
 import org.junit.Test;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
 /**
  * Test class for {@link com.goebl.simplify.Simplify}.
  *
@@ -17,7 +21,7 @@ public class Simplify3DTest {
 
     @Test
     public void testCustomPoint3DExtractor() {
-        Point3DExtractor<float[]> pointExtractor = new Point3DExtractor<float[]>() {
+        Point3DExtractor<float[]> pointExtractor = new Point3DExtractor<>() {
             @Override
             public double getX(float[] point) {
                 return point[0];
@@ -34,29 +38,29 @@ public double getZ(float[] point) {
             }
         };
 
-        Simplify3D<float[]> simplify = new Simplify3D<float[]>(new float[0][0], pointExtractor);
+        Simplify3D<float[]> simplify = new Simplify3D<>(pointExtractor);
 
-        float[][] simplified = simplify.simplify(POINTS_3D, 5.0f, false);
-        Assert.assertEquals("array should be simplified", 2, simplified.length);
+        List<float[]> simplified = simplify.simplify(Arrays.stream(POINTS_3D).toList(), 5.0f, false);
+        Assert.assertEquals("array should be simplified", 2, simplified.size());
 
-        simplified = simplify.simplify(POINTS_3D, 5.0f, true);
-        Assert.assertEquals("array should be simplified", 2, simplified.length);
+        simplified = simplify.simplify(Arrays.stream(POINTS_3D).toList(), 5.0f, true);
+        Assert.assertEquals("array should be simplified", 2, simplified.size());
     }
 
     @Test
     public void testDefaultPointExtractor() {
-        Point3D[] points = new MyPoint[POINTS_3D.length];
-        for (int i = 0; i < POINTS_3D.length; ++i) {
-            points[i] = new MyPoint(POINTS_3D[i][0], POINTS_3D[i][1], POINTS_3D[i][2]);
+        List<Point3D> points = new ArrayList<>();
+        for (float[] floats : POINTS_3D) {
+            points.add(new MyPoint(floats[0], floats[1], floats[2]));
         }
 
-        Simplify3D<Point3D> simplify3D = new Simplify3D<Point3D>(new MyPoint[0]);
+        Simplify3D<Point3D> simplify3D = new Simplify3D<>();
 
-        Point3D[] simplified = simplify3D.simplify(points, 5.0d, false);
-        Assert.assertEquals("array should be simplified", 2, simplified.length);
+        List<Point3D> simplified = simplify3D.simplify(points, 5.0d, false);
+        Assert.assertEquals("array should be simplified", 2, simplified.size());
 
         simplified = simplify3D.simplify(points, 5.0d, true);
-        Assert.assertEquals("array should be simplified", 2, simplified.length);
+        Assert.assertEquals("array should be simplified", 2, simplified.size());
     }
 
     private static class MyPoint implements Point3D {
@@ -99,9 +103,7 @@ public boolean equals(Object o) {
 
             if (Double.compare(myPoint.x, x) != 0) return false;
             if (Double.compare(myPoint.y, y) != 0) return false;
-            if (Double.compare(myPoint.z, z) != 0) return false;
-
-            return true;
+            return Double.compare(myPoint.z, z) == 0;
         }
 
     }
diff --git a/src/test/java/com/goebl/simplify/SimplifyTest.java b/src/test/java/com/goebl/simplify/SimplifyTest.java
