Issue 172: optimize map hasKey() and hasEntry()

hamcrest/src/main/java/org/hamcrest/collection/IsMapContaining.java

@@ -72,9 +72,39 @@ public static <K,V> Matcher<Map<? extends K,? extends V>> hasEntry(Matcher<? sup
      *     the value that, in combination with the key, must be describe at least one entry
      */
     public static <K,V> Matcher<Map<? extends K,? extends V>> hasEntry(K key, V value) {
-        return new IsMapContaining<>(equalTo(key), equalTo(value));
+        return new IsMapContainingEntry<>(key, value);
     }
-
+
+    /**
+     * Provides a type-safe optimization over the O(n) linear search in {@link IsMapContaining#matchesSafely(Map)},
+     * by leveraging the speed of the map's own {@link Map#containsKey(Object)} check.
+     * <p>
+     * It preserves the same descriptors.
+     */
+    private static class IsMapContainingEntry<K, V> extends IsMapContaining<K, V>
+    {
+        private final K key;
+
+        public IsMapContainingEntry(K key, V value)
+        {
+            super(equalTo(key), equalTo(value));
+            this.key = key;
+        }
+
+        @Override
+        public boolean matchesSafely(Map<? extends K, ? extends V> map)
+        {
+            try{
+                return map.containsKey(key) && super.valueMatcher.matches(map.get(key));
+            } catch (NullPointerException e){
+                // some maps (like Hashtable) don't want to let you check for a null key.
+                // to be consistent with previous behavior checking each entry,
+                // we squash any error coming from that to indicate simply that there's no entry with that key.
+                return false;
+            }
+        }
+    }
+
     /**
      * Creates a matcher for {@link java.util.Map}s matching when the examined {@link java.util.Map} contains
      * at least one key that satisfies the specified matcher.
@@ -98,7 +128,51 @@ public static <K,V> Matcher<Map<? extends K,? extends V>> hasEntry(K key, V valu
      *     the key that satisfying maps must contain
      */
     public static <K> Matcher<Map<? extends K, ?>> hasKey(K key) {
-        return new IsMapContaining<>(equalTo(key), anything());
+        return new IsMapContainingKey<>(key);
+    }
+
+    /**
+     * Provides a type-safe optimization over the O(n) linear search in {@link IsMapContaining#matchesSafely(Map)},
+     * by leveraging the speed of the map's own {@link Map#containsKey(Object)} check.
+     * <p>
+     * It preserves the same descriptors.
+     */
+    private static class IsMapContainingKey<K, V> extends IsMapContaining<K, V>
+    {
+        private final K key;
+
+        public IsMapContainingKey(K key)
+        {
+            super(equalTo(key), anything());
+            this.key = key;
+        }
+
+        @Override
+        public boolean matchesSafely(Map<? extends K, ? extends V> map)
+        {
+            try
+            {
+                return map.containsKey(key);
+            } catch (NullPointerException e){
+                // some maps (like Hashtable) don't want to let you check for a null key.
+                // to be consistent with previous behavior checking each entry,
+                // we squash any error coming from that to indicate simply that there's no entry with that key.
+                return false;
+            }
+        }
+
+        @Override
+        public void describeMismatchSafely(Map<? extends K, ? extends V> map, Description mismatchDescription)
+        {
+            mismatchDescription.appendText("map keys were ").appendValueList("[", ", ", "]", map.keySet());
+        }
+
+        @Override
+        public void describeTo(Description description)
+        {
+            description.appendText("map containing key ")
+                    .appendDescriptionOf(super.keyMatcher);
+        }
     }
 
     /**

hamcrest/src/test/java/org/hamcrest/collection/IsMapContainingKeyTest.java

@@ -4,6 +4,7 @@
 import org.hamcrest.Matcher;
 
 import java.util.HashMap;
+import java.util.Hashtable;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -62,15 +63,33 @@ public void testMatchesMapContainingKeyWithNumberKeys() throws Exception {
         assertThat(map, hasKey((Number)1));
 
         // TODO: work out the correct sprinkling of wildcards to get this to work!
-//        assertThat(map, hasKey(1));
+        //        assertThat(map, hasKey(1));
+    }
+
+    public void test_mapContainingNullKey_returnsFalse_forMapsWithNonnullKeys() throws Exception {
+        Map<Number, String> map = new Hashtable<>(); // Hashtables cannot store null keys
+        map.put(1, "A");
+        map.put(2, "B");
+
+        assertDoesNotMatch(hasKey((Number)null), map);
+    }
+
+
+    public void test_mapContainingNullKey_returnsTrue_forMapWithNullKey() throws Exception {
+        Map<Number, String> map = new HashMap<>(); // HashMap can store null keys
+        map.put(1, "A");
+        map.put(2, "B");
+        map.put(null, "C");
+
+        assertMatches(hasKey((Number)null), map);
     }
 
     public void testHasReadableDescription() {
-        assertDescription("map containing [\"a\"->ANYTHING]", hasKey("a"));
+        assertDescription("map containing key \"a\"", hasKey("a"));
     }
 
     public void testDoesNotMatchEmptyMap() {
-        assertMismatchDescription("map was []", hasKey("Foo"), new HashMap<String,Integer>());
+        assertMismatchDescription("map keys were []", hasKey("Foo"), new HashMap<String,Integer>());
     }
 
     public void testDoesNotMatchMapMissingKey() {
@@ -79,6 +98,6 @@ public void testDoesNotMatchMapMissingKey() {
         map.put("b", 2);
         map.put("c", 3);
 
-        assertMismatchDescription("map was [<a=1>, <b=2>, <c=3>]", hasKey("d"), map);
+        assertMismatchDescription("map keys were [\"a\", \"b\", \"c\"]", hasKey("d"), map);
     }
 }

hamcrest/src/test/java/org/hamcrest/collection/IsMapContainingTest.java

@@ -4,6 +4,7 @@
 import org.hamcrest.Matcher;
 
 import java.util.HashMap;
+import java.util.Hashtable;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -46,4 +47,29 @@ public void testDoesNotMatchNull() {
     public void testHasReadableDescription() {
         assertDescription("map containing [\"a\"-><2>]", hasEntry(equalTo("a"), (equalTo(2))));
     }
+
+    public void test_mapContainsEntryWithNullKey_returnsFalseForMapsWithoutNullKeys(){
+        Map<String, Integer> map = new Hashtable<>(); // throws exception if given null key, or if map.containsKey(null) is called
+        map.put("a", 1);
+        map.put("b", 2);
+
+        assertDoesNotMatch(hasEntry(null, 2), map);
+    }
+
+    public void test_mapContainsEntryWithNullKey_returnsTrueForMapWithNullKeyAndMatchingValue(){
+        Map<String, Integer> map = new HashMap<>(); // throws exception if given null key, or if map.containsKey(null) is called
+        map.put("a", 1);
+        map.put("b", 2);
+        map.put(null, 3);
+
+        assertMatches(hasEntry(null, 3), map);
+    }
+
+    public void test_mapContainsEntryWithNullKey_returnsFalseForMapWithNullKeyAndNoMatchingValue(){
+        Map<String, Integer> map = new HashMap<>(); // throws exception if given null key, or if map.containsKey(null) is called
+        map.put("a", 1);
+        map.put("b", 2);
+
+        assertDoesNotMatch(hasEntry(null, 3), map);
+    }
 }