diff --git a/src/org/jetbrains/java/decompiler/code/cfg/ControlFlowGraph.java b/src/org/jetbrains/java/decompiler/code/cfg/ControlFlowGraph.java
index 08223cf..2fd9d3c 100644
--- a/src/org/jetbrains/java/decompiler/code/cfg/ControlFlowGraph.java
+++ b/src/org/jetbrains/java/decompiler/code/cfg/ControlFlowGraph.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2017 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.
+// Copyright 2000-2020 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.java.decompiler.code.cfg;
 
 import org.jetbrains.java.decompiler.code.*;
@@ -432,7 +432,7 @@ public class ControlFlowGraph implements CodeConstants {
     }
   }
 
-  private static class JsrRecord {
+  private static final class JsrRecord {
     private final BasicBlock jsr;
     private final Set<BasicBlock> range;
     private final BasicBlock ret;
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/FinallyProcessor.java b/src/org/jetbrains/java/decompiler/modules/decompiler/FinallyProcessor.java
index 240ee3e..53a9b68 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/FinallyProcessor.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/FinallyProcessor.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2017 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
@@ -110,7 +110,7 @@ public class FinallyProcessor {
     return false;
   }
 
-  private static class Record {
+  private static final class Record {
     private final int firstCode;
     private final Map<BasicBlock, Boolean> mapLast;
 
@@ -527,7 +527,7 @@ public class FinallyProcessor {
     return true;
   }
 
-  private static class Area {
+  private static final class Area {
     private final BasicBlock start;
     private final Set<BasicBlock> sample;
     private final BasicBlock next;
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/deobfuscator/ExceptionDeobfuscator.java b/src/org/jetbrains/java/decompiler/modules/decompiler/deobfuscator/ExceptionDeobfuscator.java
index 810291d..cc02d0f 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/deobfuscator/ExceptionDeobfuscator.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/deobfuscator/ExceptionDeobfuscator.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.deobfuscator;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
@@ -20,7 +20,7 @@ import java.util.Map.Entry;
 
 public class ExceptionDeobfuscator {
 
-  private static class Range {
+  private static final class Range {
     private final BasicBlock handler;
     private final String uniqueStr;
     private final Set<BasicBlock> protectedRange;
@@ -407,7 +407,7 @@ public class ExceptionDeobfuscator {
 
       for (ExceptionRangeCFG range : ranges) {
 
-        // add some dummy instructions to prevent optimizing away the empty block  
+        // add some dummy instructions to prevent optimizing away the empty block
         SimpleInstructionSequence seq = new SimpleInstructionSequence();
         seq.addInstruction(Instruction.create(CodeConstants.opc_bipush, false, CodeConstants.GROUP_GENERAL, bytecode_version, new int[]{0}), -1);
         seq.addInstruction(Instruction.create(CodeConstants.opc_pop, false, CodeConstants.GROUP_GENERAL, bytecode_version, null), -1);
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/sforms/FlattenStatementsHelper.java b/src/org/jetbrains/java/decompiler/modules/decompiler/sforms/FlattenStatementsHelper.java
index b9abd11..ca43d66 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/sforms/FlattenStatementsHelper.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/sforms/FlattenStatementsHelper.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2017 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.sforms;
 
 import org.jetbrains.java.decompiler.modules.decompiler.StatEdge;
@@ -472,7 +472,7 @@ public class FlattenStatementsHelper {
     return mapDestinationNodes;
   }
 
-  public static class FinallyPathWrapper {
+  public static final class FinallyPathWrapper {
     public final String source;
     public final String destination;
     public final String entry;
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchAllStatement.java b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchAllStatement.java
index 376abe5..2fa2d90 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchAllStatement.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchAllStatement.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.stats;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
@@ -17,7 +17,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Set;
 
-public class CatchAllStatement extends Statement {
+public final class CatchAllStatement extends Statement {
 
   private Statement handler;
 
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchStatement.java b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchStatement.java
index 652931a..5168f05 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchStatement.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchStatement.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.stats;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
@@ -17,7 +17,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 
-public class CatchStatement extends Statement {
+public final class CatchStatement extends Statement {
   private final List<List<String>> exctstrings = new ArrayList<>();
   private final List<VarExprent> vars = new ArrayList<>();
 
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/DoStatement.java b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/DoStatement.java
index f9a149f..46b2f2c 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/DoStatement.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/DoStatement.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.stats;
 
 import org.jetbrains.java.decompiler.main.collectors.BytecodeMappingTracer;
@@ -11,7 +11,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 
-public class DoStatement extends Statement {
+public final class DoStatement extends Statement {
 
   public static final int LOOP_DO = 0;
   public static final int LOOP_DOWHILE = 1;
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/IfStatement.java b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/IfStatement.java
index bf18c51..c6a01d5 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/IfStatement.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/IfStatement.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.stats;
 
 import org.jetbrains.java.decompiler.main.collectors.BytecodeMappingTracer;
@@ -17,7 +17,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 
-public class IfStatement extends Statement {
+public final class IfStatement extends Statement {
 
   public static final int IFTYPE_IF = 0;
   public static final int IFTYPE_IFELSE = 1;
diff --git a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/SwitchStatement.java b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/SwitchStatement.java
index ab48ecc..a5b9d3a 100644
--- a/src/org/jetbrains/java/decompiler/modules/decompiler/stats/SwitchStatement.java
+++ b/src/org/jetbrains/java/decompiler/modules/decompiler/stats/SwitchStatement.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.modules.decompiler.stats;
 
 import org.jetbrains.java.decompiler.code.SwitchInstruction;
@@ -19,7 +19,7 @@ import org.jetbrains.java.decompiler.util.TextBuffer;
 
 import java.util.*;
 
-public class SwitchStatement extends Statement {
+public final class SwitchStatement extends Statement {
 
   // *****************************************************************************
   // private fields
diff --git a/src/org/jetbrains/java/decompiler/struct/attr/StructInnerClassesAttribute.java b/src/org/jetbrains/java/decompiler/struct/attr/StructInnerClassesAttribute.java
index 4306381..238900d 100644
--- a/src/org/jetbrains/java/decompiler/struct/attr/StructInnerClassesAttribute.java
+++ b/src/org/jetbrains/java/decompiler/struct/attr/StructInnerClassesAttribute.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2017 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.
+// Copyright 2000-2020 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.java.decompiler.struct.attr;
 
 import org.jetbrains.java.decompiler.struct.consts.ConstantPool;
@@ -10,7 +10,7 @@ import java.util.Collections;
 import java.util.List;
 
 public class StructInnerClassesAttribute extends StructGeneralAttribute {
-  public static class Entry {
+  public static final class Entry {
     public final int outerNameIdx;
     public final int simpleNameIdx;
     public final int accessFlags;
diff --git a/src/org/jetbrains/java/decompiler/struct/attr/StructLocalVariableTableAttribute.java b/src/org/jetbrains/java/decompiler/struct/attr/StructLocalVariableTableAttribute.java
index 15fb317..66eb593 100644
--- a/src/org/jetbrains/java/decompiler/struct/attr/StructLocalVariableTableAttribute.java
+++ b/src/org/jetbrains/java/decompiler/struct/attr/StructLocalVariableTableAttribute.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.struct.attr;
 
 import org.jetbrains.java.decompiler.struct.consts.ConstantPool;
@@ -71,7 +71,7 @@ public class StructLocalVariableTableAttribute extends StructGeneralAttribute {
     return localVariables.stream().filter(v -> v.start_pc == 0).collect(Collectors.toMap(v -> v.index, v -> v.name, (n1, n2) -> n2));
   }
 
-  private static class LocalVariable {
+  private static final class LocalVariable {
     final int start_pc;
     final int length;
     final String name;
diff --git a/src/org/jetbrains/java/decompiler/struct/gen/FieldDescriptor.java b/src/org/jetbrains/java/decompiler/struct/gen/FieldDescriptor.java
index 94add14..50d41ba 100644
--- a/src/org/jetbrains/java/decompiler/struct/gen/FieldDescriptor.java
+++ b/src/org/jetbrains/java/decompiler/struct/gen/FieldDescriptor.java
@@ -1,9 +1,9 @@
-// Copyright 2000-2017 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.
+// Copyright 2000-2020 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.java.decompiler.struct.gen;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
 
-public class FieldDescriptor {
+public final class FieldDescriptor {
 
   public static final FieldDescriptor INTEGER_DESCRIPTOR = parseDescriptor("Ljava/lang/Integer;");
   public static final FieldDescriptor LONG_DESCRIPTOR = parseDescriptor("Ljava/lang/Long;");
diff --git a/src/org/jetbrains/java/decompiler/struct/gen/MethodDescriptor.java b/src/org/jetbrains/java/decompiler/struct/gen/MethodDescriptor.java
index 102393c..8697b03 100644
--- a/src/org/jetbrains/java/decompiler/struct/gen/MethodDescriptor.java
+++ b/src/org/jetbrains/java/decompiler/struct/gen/MethodDescriptor.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2017 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.
+// Copyright 2000-2020 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.java.decompiler.struct.gen;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
@@ -7,7 +7,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-public class MethodDescriptor {
+public final class MethodDescriptor {
   public final VarType[] params;
   public final VarType ret;
 
diff --git a/src/org/jetbrains/java/decompiler/util/FastFixedSetFactory.java b/src/org/jetbrains/java/decompiler/util/FastFixedSetFactory.java
index d05b7d4..7c2956c 100644
--- a/src/org/jetbrains/java/decompiler/util/FastFixedSetFactory.java
+++ b/src/org/jetbrains/java/decompiler/util/FastFixedSetFactory.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.util;
 
 import java.util.Collection;
@@ -46,7 +46,7 @@ public class FastFixedSetFactory<E> {
     return colValuesInternal;
   }
 
-  public static class FastFixedSet<E> implements Iterable<E> {
+  public static final class FastFixedSet<E> implements Iterable<E> {
 
     private final FastFixedSetFactory<E> factory;
 
@@ -242,7 +242,7 @@ public class FastFixedSetFactory<E> {
     }
   }
 
-  public static class FastFixedSetIterator<E> implements Iterator<E> {
+  public static final class FastFixedSetIterator<E> implements Iterator<E> {
 
     private final VBStyleCollection<int[], E> colValuesInternal;
     private final int[] data;
diff --git a/src/org/jetbrains/java/decompiler/util/FastSparseSetFactory.java b/src/org/jetbrains/java/decompiler/util/FastSparseSetFactory.java
index b955139..a99083c 100644
--- a/src/org/jetbrains/java/decompiler/util/FastSparseSetFactory.java
+++ b/src/org/jetbrains/java/decompiler/util/FastSparseSetFactory.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2018 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.
+// Copyright 2000-2020 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.java.decompiler.util;
 
 import java.util.Collection;
@@ -69,7 +69,7 @@ public class FastSparseSetFactory<E> {
   }
 
 
-  public static class FastSparseSet<E> implements Iterable<E> {
+  public static final class FastSparseSet<E> implements Iterable<E> {
     public static final FastSparseSet[] EMPTY_ARRAY = new FastSparseSet[0];
 
     private final FastSparseSetFactory<E> factory;
@@ -360,7 +360,7 @@ public class FastSparseSetFactory<E> {
     }
   }
 
-  public static class FastSparseSetIterator<E> implements Iterator<E> {
+  public static final class FastSparseSetIterator<E> implements Iterator<E> {
 
     private final VBStyleCollection<int[], E> colValuesInternal;
     private final int[] data;