properly fixes #340

Author: erosb

core/src/main/java/org/everit/json/schema/regexp/JavaUtilRegexpFactory.java

@@ -27,7 +27,7 @@ class JavaUtilRegexp extends AbstractRegexp {
         if (!(o instanceof JavaUtilRegexp))
             return false;
         JavaUtilRegexp that = (JavaUtilRegexp) o;
-        return Objects.equals(pattern, that.pattern);
+        return Objects.equals(pattern.pattern(), that.pattern.pattern());
     }
 
     @Override public int hashCode() {

core/src/test/java/org/everit/json/schema/regexp/JavaUtilRegexpTest.java

@@ -39,7 +39,7 @@ public void asString() {
     public void equalsVerifier() {
         EqualsVerifier.forClass(JavaUtilRegexp.class)
             .withPrefabValues(Pattern.class, Pattern.compile("red"), Pattern.compile("black"))
-            .withIgnoredFields("asString")
+            .withIgnoredFields("asString").withNonnullFields("pattern")
             .suppress(Warning.STRICT_INHERITANCE)
             .verify();
     }