Use *=

src/test/java/org/apache/commons/collections4/map/ReferenceIdentityMapTest.java

@@ -322,7 +322,7 @@ public class ReferenceIdentityMapTest<K, V> extends AbstractIterableMapTest<K, V
             // create garbage:
             @SuppressWarnings("unused")
             final byte[] b =  new byte[bytz];
-            bytz = bytz * 2;
+            bytz *= 2;
         }
     }
 

src/test/java/org/apache/commons/collections4/map/ReferenceMapTest.java

@@ -252,7 +252,7 @@ public class ReferenceMapTest<K, V> extends AbstractIterableMapTest<K, V> {
             // create garbage:
             @SuppressWarnings("unused")
             final byte[] b = new byte[bytz];
-            bytz = bytz * 2;
+            bytz *= 2;
         }
     }
 
@@ -286,7 +286,7 @@ public class ReferenceMapTest<K, V> extends AbstractIterableMapTest<K, V> {
             // create garbage:
             @SuppressWarnings("unused")
             final byte[] b = new byte[bytz];
-            bytz = bytz * 2;
+            bytz *= 2;
         }
         assertFalse(expiredValues.isEmpty(), "Value should be stored");
     }