IsEqual method delegates to the object's equals() method for null values.

joe.walnes · joe.walnes · commit 873014eaaba5 · 2007-10-22T19:12:40.000Z
See http://code.google.com/p/hamcrest/issues/detail?id=22 (Thanks RoystonS)
diff --git a/hamcrest-core/src/main/java/org/hamcrest/core/IsEqual.java b/hamcrest-core/src/main/java/org/hamcrest/core/IsEqual.java
@@ -22,16 +22,16 @@ public IsEqual(T equalArg) {
     }
 
     public boolean matches(Object arg) {
-        return areEqual(object, arg);
+        return areEqual(arg, object);
     }
 
     public void describeTo(Description description) {
         description.appendValue(object);
     }
     
 	private static boolean areEqual(Object o1, Object o2) {
-        if (o1 == null || o2 == null) {
-            return o1 == null && o2 == null;
+        if (o1 == null) {
+            return o2 == null;
         } else if (isArray(o1)) {
             return isArray(o2) && areArraysEqual(o1, o2);
         } else {
diff --git a/hamcrest-unit-test/src/main/java/org/hamcrest/core/IsEqualTest.java b/hamcrest-unit-test/src/main/java/org/hamcrest/core/IsEqualTest.java
@@ -30,6 +30,22 @@ public void testCanCompareNullValues() {
         assertThat("hi", not(equalTo(null)));
     }
 
+    public void testHonoursIsEqualImplementationEvenWithNullValues() {
+        Object alwaysEqual = new Object() {
+            public boolean equals(Object obj) {
+                return true;
+            }
+        };
+        Object neverEqual = new Object() {
+            public boolean equals(Object obj) {
+                return false;
+            }
+        };
+
+        assertThat(alwaysEqual, equalTo(null));
+        assertThat(neverEqual, not(equalTo(null)));
+    }
+    
     public void testComparesTheElementsOfAnObjectArray() {
         String[] s1 = {"a", "b"};
         String[] s2 = {"a", "b"};

Original file line number	Diff line number	Diff line change
`@@ -22,16 +22,16 @@ public IsEqual(T equalArg) {`
`22`	`22`	`}`
`23`	`23`
`24`	`24`	`public boolean matches(Object arg) {`
`25`		`- return areEqual(object, arg);`
	`25`	`+ return areEqual(arg, object);`
`26`	`26`	`}`
`27`	`27`
`28`	`28`	`public void describeTo(Description description) {`
`29`	`29`	`description.appendValue(object);`
`30`	`30`	`}`
`31`	`31`
`32`	`32`	`private static boolean areEqual(Object o1, Object o2) {`
`33`		`- if (o1 == null \|\| o2 == null) {`
`34`		`- return o1 == null && o2 == null;`
	`33`	`+ if (o1 == null) {`
	`34`	`+ return o2 == null;`
`35`	`35`	`} else if (isArray(o1)) {`
`36`	`36`	`return isArray(o2) && areArraysEqual(o1, o2);`
`37`	`37`	`} else {`