fixing issue #89 and adding tests

Author: bocops

java/com/google/openlocationcode/OpenLocationCode.java

@@ -149,7 +149,7 @@ public double getEastLongitude() {
   /**
    * Creates Open Location Code object for the provided code.
    * @param code A valid OLC code. Can be a full code or a shortened code.
-   * @throws IlegalArgumentException when the passed code is not valid.
+   * @throws IllegalArgumentException when the passed code is not valid.
    * @constructor
   */
   public OpenLocationCode(String code) throws IllegalArgumentException {
@@ -432,11 +432,14 @@ public OpenLocationCode recover(double referenceLatitude, double referenceLongit
     double recoveredLatitude = recoveredCodeArea.getCenterLatitude();
     double recoveredLongitude = recoveredCodeArea.getCenterLongitude();
 
-    // Move the recovered latitude by one precision up or down if it is too far from the reference.
+    // Move the recovered latitude by one precision up or down if it is too far from the reference,
+    // unless doing so would lead to an invalid latitude.
     double latitudeDiff = recoveredLatitude - referenceLatitude;
-    if (latitudeDiff > prefixPrecision / 2) {
+    if (latitudeDiff > prefixPrecision / 2
+            && recoveredLatitude - prefixPrecision > -LATITUDE_MAX.intValue()) {
       recoveredLatitude -= prefixPrecision;
-    } else if (latitudeDiff < -prefixPrecision / 2) {
+    } else if (latitudeDiff < -prefixPrecision / 2
+            && recoveredLatitude + prefixPrecision < LATITUDE_MAX.intValue()) {
       recoveredLatitude += prefixPrecision;
     }
 

java/com/google/openlocationcode/tests/RecoverTest.java

@@ -0,0 +1,22 @@
+package com.google.openlocationcode.tests;
+
+import com.google.openlocationcode.OpenLocationCode;
+
+import junit.framework.Assert;
+import org.junit.Test;
+
+/** Test recovery near the poles. */
+public class RecoverTest {
+
+    @Test
+    public void testRecoveryNearSouthPole() {
+        OpenLocationCode olc = new OpenLocationCode("XXXXXX+XX");
+        Assert.assertEquals("2CXXXXXX+XX",olc.recover(-81.0,0.0).getCode());
+    }
+
+    @Test
+    public void testRecoveryNearNorthPole() {
+        OpenLocationCode olc = new OpenLocationCode("2222+22");
+        Assert.assertEquals("CFX22222+22", olc.recover(89.6, 0.0).getCode());
+    }
+}