diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/control/finalVar/InvalidWriteAccessSearcher.java b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/control/finalVar/InvalidWriteAccessSearcher.java
index 4117146a060e..b43981bf2b07 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/control/finalVar/InvalidWriteAccessSearcher.java
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/control/finalVar/InvalidWriteAccessSearcher.java
@@ -5,9 +5,9 @@ import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.GrVariable;
-import org.jetbrains.plugins.groovy.lang.psi.controlFlow.VariableDescriptor;
 import org.jetbrains.plugins.groovy.lang.psi.controlFlow.Instruction;
 import org.jetbrains.plugins.groovy.lang.psi.controlFlow.ReadWriteVariableInstruction;
+import org.jetbrains.plugins.groovy.lang.psi.controlFlow.VariableDescriptor;
 import org.jetbrains.plugins.groovy.lang.psi.controlFlow.impl.VariableDescriptorFactory;
 import org.jetbrains.plugins.groovy.lang.psi.dataFlow.DFAEngine;
 import org.jetbrains.plugins.groovy.lang.psi.dataFlow.DfaInstance;
@@ -84,11 +84,6 @@ public class InvalidWriteAccessSearcher {
     public MyData join(@NotNull List<? extends MyData> ins) {
       return new MyData(ins);
     }
-
-    @Override
-    public boolean eq(@NotNull MyData e1, @NotNull MyData e2) {
-      return e1.equals(e2);
-    }
   }
 
   private static class MyData {
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/dataflow/WritesCounterSemilattice.java b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/dataflow/WritesCounterSemilattice.java
index ac8abc999bf0..f08c1c7cf985 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/dataflow/WritesCounterSemilattice.java
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/dataflow/WritesCounterSemilattice.java
@@ -1,18 +1,4 @@
-/*
- * Copyright 2000-2017 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.plugins.groovy.codeInspection.dataflow;
 
 import gnu.trove.TObjectIntHashMap;
@@ -46,9 +32,4 @@ public class WritesCounterSemilattice<T> implements Semilattice<TObjectIntHashMa
     }
     return result;
   }
-
-  @Override
-  public boolean eq(@NotNull TObjectIntHashMap<T> e1, @NotNull TObjectIntHashMap<T> e2) {
-    return e1.equals(e2);
-  }
 }
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/utils/ControlFlowUtils.java b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/utils/ControlFlowUtils.java
index a1b45045915f..237eaf467ba1 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/utils/ControlFlowUtils.java
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/codeInspection/utils/ControlFlowUtils.java
@@ -780,11 +780,6 @@ public class ControlFlowUtils {
         }
         return result;
       }
-
-      @Override
-      public boolean eq(@NotNull BitSet e1, @NotNull BitSet e2) {
-        return e1.equals(e2);
-      }
     };
 
     DfaInstance<BitSet> dfa = new DfaInstance<BitSet>() {
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/dataFlow/Semilattice.java b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/dataFlow/Semilattice.java
index 0ea1fd447500..0b67921359a6 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/dataFlow/Semilattice.java
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/psi/dataFlow/Semilattice.java
@@ -1,31 +1,16 @@
-/*
- * Copyright 2000-2017 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.plugins.groovy.lang.psi.dataFlow;
 
 import org.jetbrains.annotations.NotNull;
 
 import java.util.List;
 
-/**
- * @author ven
- */
 public interface Semilattice<E> {
 
   @NotNull
   E join(@NotNull List<? extends E> ins);
 
-  boolean eq(@NotNull E e1, @NotNull E e2);
+  default boolean eq(@NotNull E e1, @NotNull E e2) {
+    return e1.equals(e2);
+  }
 }