Code cleanup and modernization:

querydsl-libraries/querydsl-collections/src/main/java/com/querydsl/collections/CollQueryFunctions.java

@@ -85,7 +85,7 @@ public Number apply(Number num1, Number num2) {
         }
       };
 
-  private static final List<Object> nullList = Collections.singletonList((Object) null);
+  private static final List<Object> nullList = Collections.singletonList(null);
 
   @SuppressWarnings("unused")
   public static boolean equals(Object o1, Object o2) {
@@ -231,7 +231,7 @@ public static Number aggregate(
     } else if (aggregator == Ops.AggOps.COUNT_AGG) {
       return (long) source.size();
     } else if (aggregator == Ops.AggOps.COUNT_DISTINCT_AGG) {
-      if (!Set.class.isInstance(source)) {
+      if (!(source instanceof Set)) {
         source = new HashSet<>(source);
       }
       return (long) source.size();

querydsl-libraries/querydsl-collections/src/main/java/com/querydsl/collections/CollQuerySerializer.java

@@ -164,7 +164,7 @@ public Void visit(SubQueryExpression<?> expr, Void context) {
   }
 
   private void visitCast(Operator operator, Expression<?> source, Class<?> targetType) {
-    if (Number.class.isAssignableFrom(source.getType()) && !Constant.class.isInstance(source)) {
+    if (Number.class.isAssignableFrom(source.getType()) && !(source instanceof Constant)) {
       append("new ").append(source.getType().getSimpleName()).append("(");
       handle(source);
       append(")");

querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/DefaultQueryMetadata.java

@@ -31,7 +31,6 @@
 import java.io.Serial;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -252,12 +251,7 @@ public List<JoinExpression> getJoins() {
       return Collections.unmodifiableList(joins);
     } else {
       List<JoinExpression> j = new ArrayList<>(joins);
-      j.add(
-          new JoinExpression(
-              joinType,
-              joinTarget,
-              joinCondition,
-              Collections.unmodifiableSet(new HashSet<>(joinFlags))));
+      j.add(new JoinExpression(joinType, joinTarget, joinCondition, Set.copyOf(joinFlags)));
       return j;
     }
   }

querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/alias/AliasFactory.java

@@ -165,7 +165,7 @@ public <A extends Expression<?>> A getCurrentAndReset() {
 
   /** Reset the thread bound expression to null */
   public void reset() {
-    current.set(null);
+    current.remove();
   }
 
   /**

querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/types/ExpressionUtils.java

@@ -558,7 +558,7 @@ public static Expression<String> likeToRegex(Expression<String> expr, boolean ma
       if (matchStartAndEnd && !like.endsWith("%")) {
         rv.append('$');
       }
-      if (!like.equals(rv.toString())) {
+      if (!like.contentEquals(rv)) {
         return ConstantImpl.create(rv.toString());
       }
     } else if (expr instanceof Operation<?> o) {

querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/util/BeanMap.java

@@ -564,8 +564,9 @@ private void initialise() {
   }
 
   /**
-   * Called during a successful {@link #put(Object,Object)} operation. Default implementation does
-   * nothing. Override to be notified of property changes in the bean caused by this map.
+   * Called during a successful {@link #put(String, Object)} (Object,Object)} operation. Default
+   * implementation does nothing. Override to be notified of property changes in the bean caused by
+   * this map.
    *
    * @param key the name of the property that changed
    * @param oldValue the old value for that property

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/Conversions.java

@@ -71,12 +71,12 @@ private static boolean needsConstantRemoval(Expression<?> expr) {
 
   private static boolean needsNumberConversion(Expression<?> expr) {
     expr = ExpressionUtils.extract(expr);
-    return Number.class.isAssignableFrom(expr.getType()) && !Path.class.isInstance(expr);
+    return Number.class.isAssignableFrom(expr.getType()) && !(expr instanceof Path);
   }
 
   private static boolean isEntityPathAndNeedsWrapping(Expression<?> expr) {
     if ((expr instanceof Path && expr.getType().isAnnotationPresent(Entity.class))
-        || (expr instanceof EntityPath && !RelationalPath.class.isInstance(expr))) {
+        || (expr instanceof EntityPath && !(expr instanceof RelationalPath))) {
       Path<?> path = (Path<?>) expr;
       if (path.getMetadata().getParent() == null) {
         return true;

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/JPAExpressions.java

@@ -144,7 +144,7 @@ public static <U extends BeanPath<? extends T>, T> U treat(
   public static <A extends Comparable<? super A>> ComparableExpression<A> avg(
       CollectionExpression<?, A> col) {
     return Expressions.comparableOperation(
-        (Class) col.getParameter(0), Ops.QuantOps.AVG_IN_COL, (Expression<?>) col);
+        (Class) col.getParameter(0), Ops.QuantOps.AVG_IN_COL, col);
   }
 
   /**
@@ -156,7 +156,7 @@ public static <A extends Comparable<? super A>> ComparableExpression<A> avg(
   public static <A extends Comparable<? super A>> ComparableExpression<A> max(
       CollectionExpression<?, A> left) {
     return Expressions.comparableOperation(
-        (Class) left.getParameter(0), Ops.QuantOps.MAX_IN_COL, (Expression<?>) left);
+        (Class) left.getParameter(0), Ops.QuantOps.MAX_IN_COL, left);
   }
 
   /**
@@ -168,7 +168,7 @@ public static <A extends Comparable<? super A>> ComparableExpression<A> max(
   public static <A extends Comparable<? super A>> ComparableExpression<A> min(
       CollectionExpression<?, A> left) {
     return Expressions.comparableOperation(
-        (Class) left.getParameter(0), Ops.QuantOps.MIN_IN_COL, (Expression<?>) left);
+        (Class) left.getParameter(0), Ops.QuantOps.MIN_IN_COL, left);
   }
 
   /**

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/JPQLSerializer.java

@@ -320,7 +320,7 @@ public void serializeForInsert(
         first = false;
       }
       append(")");
-    } else if (inserts != null && inserts.entrySet().size() > 0) {
+    } else if (inserts != null && !inserts.isEmpty()) {
       first = true;
       for (Map.Entry<Path<?>, Expression<?>> entry : inserts.entrySet()) {
         if (!first) {

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/NativeSQLSerializer.java

@@ -120,12 +120,8 @@ public void serialize(QueryMetadata metadata, boolean forCountRow) {
     Expression<?> projection = metadata.getProjection();
     if (projection instanceof Path) {
       Path<?> path = (Path<?>) projection;
-      if (!used.add(path.getMetadata().getName())) {
-        var alias = "col_1";
-        aliases.computeIfAbsent(projection, NativeSQLSerializer::createArrayList).add(alias);
-        projection = ExpressionUtils.as(projection, alias);
-        modified = true;
-      } else if (path.getAnnotatedElement().isAnnotationPresent(Column.class)) {
+      used.add(path.getMetadata().getName());
+      if (path.getAnnotatedElement().isAnnotationPresent(Column.class)) {
         var column = path.getAnnotatedElement().getAnnotation(Column.class);
         if (!column.name().isEmpty()) {
           aliases

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/hibernate/HibernateUtil.java

@@ -18,12 +18,10 @@
 import com.querydsl.core.types.dsl.Param;
 import java.math.BigDecimal;
 import java.math.BigInteger;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -38,33 +36,31 @@
 public final class HibernateUtil {
 
   private static final Set<Class<?>> BUILT_IN =
-      Collections.unmodifiableSet(
-          new HashSet<>(
-              Arrays.asList(
-                  Boolean.class,
-                  Byte.class,
-                  Character.class,
-                  Double.class,
-                  Float.class,
-                  Integer.class,
-                  Long.class,
-                  Short.class,
-                  String.class,
-                  BigDecimal.class,
-                  byte[].class,
-                  Byte[].class,
-                  java.util.Date.class,
-                  java.util.Calendar.class,
-                  java.sql.Date.class,
-                  java.sql.Time.class,
-                  java.sql.Timestamp.class,
-                  java.util.Locale.class,
-                  java.util.TimeZone.class,
-                  java.util.Currency.class,
-                  Class.class,
-                  java.io.Serializable.class,
-                  java.sql.Blob.class,
-                  java.sql.Clob.class)));
+      Set.of(
+          Boolean.class,
+          Byte.class,
+          Character.class,
+          Double.class,
+          Float.class,
+          Integer.class,
+          Long.class,
+          Short.class,
+          String.class,
+          BigDecimal.class,
+          byte[].class,
+          Byte[].class,
+          java.util.Date.class,
+          java.util.Calendar.class,
+          java.sql.Date.class,
+          java.sql.Time.class,
+          java.sql.Timestamp.class,
+          java.util.Locale.class,
+          java.util.TimeZone.class,
+          java.util.Currency.class,
+          Class.class,
+          java.io.Serializable.class,
+          java.sql.Blob.class,
+          java.sql.Clob.class);
 
   private static final Map<Class<?>, BasicTypeReference<?>> TYPES;
 

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/hibernate/sql/AbstractHibernateSQLQuery.java

@@ -113,11 +113,9 @@ private Query createQuery(boolean forCount) {
         query.addEntity(extractEntityExpression(projection).toString(), projection.getType());
       } else if (aliases.containsKey(projection)) {
         for (String scalar : aliases.get(projection)) {
-          if (!used.contains(scalar)) {
-            query.addScalar(scalar);
-            used.add(scalar);
-            break;
-          }
+          query.addScalar(scalar);
+          used.add(scalar);
+          break;
         }
       }
 

querydsl-libraries/querydsl-jpa/src/main/java/com/querydsl/jpa/sql/AbstractJPASQLQuery.java

@@ -134,11 +134,9 @@ && isEntityExpression(projection)) {
             query, extractEntityExpression(projection).toString(), projection.getType());
       } else if (aliases.containsKey(projection)) {
         for (String scalar : aliases.get(projection)) {
-          if (!used.contains(scalar)) {
-            queryHandler.addScalar(query, scalar, projection.getType());
-            used.add(scalar);
-            break;
-          }
+          queryHandler.addScalar(query, scalar, projection.getType());
+          used.add(scalar);
+          break;
         }
       }
     }

querydsl-libraries/querydsl-mongodb/src/main/java/com/querydsl/mongodb/document/MongodbDocumentSerializer.java

@@ -409,7 +409,7 @@ private Queue<Map<Object, Object>> collectConnectorArgs(String operator, Operati
     Queue<Map<Object, Object>> pendingDocuments = new LinkedList<>();
     for (Expression<?> exp : operation.getArgs()) {
       var document = (Map<Object, Object>) handle(exp);
-      if (document.keySet().size() == 1 && document.containsKey(operator)) {
+      if (document.size() == 1 && document.containsKey(operator)) {
         pendingDocuments.addAll((Collection<Map<Object, Object>>) document.get(operator));
       } else {
         pendingDocuments.add(document);

querydsl-libraries/querydsl-r2dbc/src/main/java/com/querydsl/r2dbc/SQLSerializer.java

@@ -1001,19 +1001,13 @@ protected void visitOperation(
 
     } else if (operator == Ops.ALIAS) {
       if (stage == Stage.SELECT || stage == Stage.FROM) {
-        if (stage == SQLSerializer.Stage.SELECT || stage == SQLSerializer.Stage.FROM) {
-          if (args.get(1) instanceof Path && !((Path<?>) args.get(1)).getMetadata().isRoot()) {
-            Path<?> path = (Path<?>) args.get(1);
-            args =
-                Arrays.asList(
-                    args.get(0),
-                    ExpressionUtils.path(path.getType(), path.getMetadata().getName()));
-          }
-          super.visitOperation(type, operator, args);
-        } else {
-          // handle only target
-          handle(args.get(1));
+        if (args.get(1) instanceof Path && !((Path<?>) args.get(1)).getMetadata().isRoot()) {
+          Path<?> path = (Path<?>) args.get(1);
+          args =
+              Arrays.asList(
+                  args.get(0), ExpressionUtils.path(path.getType(), path.getMetadata().getName()));
         }
+        super.visitOperation(type, operator, args);
       } else {
         // handle only target
         handle(args.get(1));
@@ -1035,28 +1029,24 @@ protected void visitOperation(
         if (templates.getListMaxSize() == 0 || coll.size() <= templates.getListMaxSize()) {
           super.visitOperation(type, operator, args);
         } else {
-          if (templates.getListMaxSize() == 0 || coll.size() <= templates.getListMaxSize()) {
-            super.visitOperation(type, operator, args);
+          // The type of the path is compatible with the constant
+          // expression, since the compile time checking mandates it to be
+          @SuppressWarnings("unchecked")
+          var path = (Expression<Object>) args.get(0);
+          if (pathAdded) {
+            constantPaths.removeLast();
+          }
+          Iterable<List<Object>> partitioned =
+              CollectionUtils.partition(new ArrayList<>(coll), templates.getListMaxSize());
+          Predicate result;
+          if (operator == Ops.IN) {
+            result = ExpressionUtils.inAny(path, partitioned);
           } else {
-            // The type of the path is compatible with the constant
-            // expression, since the compile time checking mandates it to be
-            @SuppressWarnings("unchecked")
-            var path = (Expression<Object>) args.get(0);
-            if (pathAdded) {
-              constantPaths.removeLast();
-            }
-            Iterable<List<Object>> partitioned =
-                CollectionUtils.partition(new ArrayList<>(coll), templates.getListMaxSize());
-            Predicate result;
-            if (operator == Ops.IN) {
-              result = ExpressionUtils.inAny(path, partitioned);
-            } else {
-              result = ExpressionUtils.notInAny(path, partitioned);
-            }
-            append("(");
-            result.accept(this, null);
-            append(")");
+            result = ExpressionUtils.notInAny(path, partitioned);
           }
+          append("(");
+          result.accept(this, null);
+          append(")");
         }
       }
 

querydsl-libraries/querydsl-sql/src/main/java/com/querydsl/sql/RelationalPathUtils.java

@@ -45,7 +45,7 @@ public static <T> FactoryExpression<T> createProjection(RelationalPath<T> path)
 
   private static <T> FactoryExpression<T> createConstructorProjection(RelationalPath<T> path) {
     Expression<?>[] exprs = path.getColumns().toArray(new Expression[0]);
-    return Projections.<T>constructor((Class) path.getType(), exprs);
+    return Projections.constructor(path.getType(), exprs);
   }
 
   private static <T> FactoryExpression<T> createBeanProjection(RelationalPath<T> path) {
@@ -56,7 +56,7 @@ private static <T> FactoryExpression<T> createBeanProjection(RelationalPath<T> p
     if (bindings.isEmpty()) {
       throw new IllegalArgumentException("No bindings could be derived from " + path);
     }
-    return Projections.<T>fields((Class) path.getType(), bindings);
+    return Projections.fields(path.getType(), bindings);
   }
 
   private RelationalPathUtils() {}

querydsl-libraries/querydsl-sql/src/main/java/com/querydsl/sql/SQLSerializer.java

@@ -971,7 +971,7 @@ public void visitConstant(Object constant) {
       }
     } else {
       if (stage == Stage.SELECT
-          && !Null.class.isInstance(constant)
+          && !(constant instanceof Null)
           && configuration.getTemplates().isWrapSelectParameters()) {
         var typeName = configuration.getTypeNameForCast(constant.getClass());
         Expression type = Expressions.constant(typeName);
@@ -1079,7 +1079,7 @@ protected void visitOperation(
         && args.get(1) instanceof Constant<?>
         && operator != Ops.NUMCAST) {
       Object constant = ((Constant<?>) args.get(1)).getConstant();
-      if (!Collection.class.isInstance(constant) || !((Collection) constant).isEmpty()) {
+      if (!(constant instanceof Collection) || !((Collection) constant).isEmpty()) {
         for (Element element : templates.getTemplate(operator).getElements()) {
           if (element instanceof Template.ByIndex && ((Template.ByIndex) element).getIndex() == 1) {
             constantPaths.add((Path<?>) args.get(0));