[refactor] Address Codacy findings from PR eXist-db#6344 review

Per reinhapa's review:
- FunReplace, FunTokenize: drop fully-qualified RegexUtil.* prefixes
  since `import static org.exist.xquery.regex.RegexUtil.*` already
  pulls hasXPath4Lookaround / translateXPath4Lookaround /
  validateXPathRegex into scope.
- SequenceType: drop redundant `= null` initializers on the two new
  function-test fields; combine the two pairs of nested-if checks in
  checkType / checkFunctionType into single conjunctions.
- ContainsTokenEmptyCollationTest: rename test methods to
  lowerCamelCase (drop underscores) to satisfy JUnit 4 name pattern.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: joewiz

exist-core/src/main/java/org/exist/xquery/functions/fn/FunReplace.java

@@ -134,8 +134,8 @@ public Sequence eval(final Sequence[] args, final Sequence contextSequence) thro
 			final boolean isXQuery40 = context.getXQueryVersion() >= 40;
 
 			// XQ4: translate (*positive_lookahead:...) etc. to Java regex (?=...) syntax
-			if (isXQuery40 && org.exist.xquery.regex.RegexUtil.hasXPath4Lookaround(pattern)) {
-				pattern = org.exist.xquery.regex.RegexUtil.translateXPath4Lookaround(pattern);
+			if (isXQuery40 && hasXPath4Lookaround(pattern)) {
+				pattern = translateXPath4Lookaround(pattern);
 			}
 
 			// Pre-validate: reject constructs not valid in XPath regex

exist-core/src/main/java/org/exist/xquery/functions/fn/FunTokenize.java

@@ -98,13 +98,13 @@ public Sequence eval(final Sequence[] args, final Sequence contextSequence) thro
                     String rawPattern = args[1].itemAt(0).getStringValue();
 
                     // XQ4: translate (*positive_lookahead:...) etc. to Java regex
-                    if (isXQuery40 && org.exist.xquery.regex.RegexUtil.hasXPath4Lookaround(rawPattern)) {
-                        rawPattern = org.exist.xquery.regex.RegexUtil.translateXPath4Lookaround(rawPattern);
+                    if (isXQuery40 && hasXPath4Lookaround(rawPattern)) {
+                        rawPattern = translateXPath4Lookaround(rawPattern);
                     }
 
                     // Pre-validate: reject constructs not valid in XPath regex
                     if (!hasLiteral(flags)) {
-                        org.exist.xquery.regex.RegexUtil.validateXPathRegex(this, rawPattern, isXQuery40);
+                        validateXPathRegex(this, rawPattern, isXQuery40);
                     }
 
                     if (hasLiteral(flags)) {

exist-core/src/main/java/org/exist/xquery/value/SequenceType.java

@@ -42,8 +42,8 @@ public class SequenceType {
     private int primaryType = Type.ITEM;
     private Cardinality cardinality = Cardinality.EXACTLY_ONE;
     private QName nodeName = null;
-    private SequenceType[] functionParamTypes = null;
-    private SequenceType functionReturnType = null;
+    private SequenceType[] functionParamTypes;
+    private SequenceType functionReturnType;
 
     public SequenceType() {
     }
@@ -178,10 +178,9 @@ public boolean checkType(final Item item) {
         }
 
         // For function types, check parameter and return type compatibility
-        if (Type.subTypeOf(primaryType, Type.FUNCTION) && item instanceof FunctionReference) {
-            if (!checkFunctionType((FunctionReference) item)) {
-                return false;
-            }
+        if (Type.subTypeOf(primaryType, Type.FUNCTION) && item instanceof FunctionReference
+                && !checkFunctionType((FunctionReference) item)) {
+            return false;
         }
 
         if (nodeName == null) {
@@ -217,10 +216,8 @@ private boolean checkFunctionType(final FunctionReference funcRef) {
         final FunctionSignature sig = funcRef.getSignature();
 
         // Check arity: if we have typed parameter info, check against it
-        if (functionParamTypes != null) {
-            if (sig.getArgumentCount() != functionParamTypes.length) {
-                return false;
-            }
+        if (functionParamTypes != null && sig.getArgumentCount() != functionParamTypes.length) {
+            return false;
         }
 
         // Check return type: function's return type must be a subtype of required return type (covariant)

exist-core/src/test/java/org/exist/xquery/functions/fn/ContainsTokenEmptyCollationTest.java

@@ -48,21 +48,21 @@ public class ContainsTokenEmptyCollationTest {
     public static final ExistEmbeddedServer existEmbeddedServer = new ExistEmbeddedServer(true, true);
 
     @Test
-    public void emptyCollation_emptySequenceLiteral() throws Exception {
+    public void emptyCollationEmptySequenceLiteral() throws Exception {
         // contains-token-80: third arg is ()
         assertEquals("true",
                 executeStringValue("fn:contains-token('a b c', 'b', ())"));
     }
 
     @Test
-    public void emptyCollation_emptyStringSequence() throws Exception {
+    public void emptyCollationEmptyStringSequence() throws Exception {
         // contains-token-82: third arg comes from a let returning empty sequence
         assertEquals("true",
                 executeStringValue("let $c := () return fn:contains-token('a b c', 'b', $c)"));
     }
 
     @Test
-    public void presentCollation_stillWorks() throws Exception {
+    public void presentCollationStillWorks() throws Exception {
         assertEquals("true",
                 executeStringValue("fn:contains-token('a b c', 'B', " +
                         "'http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive')"));