Not used IntegerHolder class removed (#8747)

Motivation:

IntergerHolder was left from some old days and not used anymore.

Modification:

Remove IntergerHolder from the codebase.

Result:

Removed unused code

common/src/main/java/io/netty/util/internal/IntegerHolder.java

@@ -1,25 +0,0 @@
-/*
- * Copyright 2014 The Netty Project
- *
- * The Netty Project licenses this file to you 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.
- */
-
-package io.netty.util.internal;
-
-/**
- * @deprecated For removal in netty 4.2
- */
-@Deprecated
-public final class IntegerHolder {
-    public int value;
-}

common/src/main/java/io/netty/util/internal/InternalThreadLocalMap.java

@@ -144,9 +144,6 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
         if (handlerSharableCache != null) {
             count ++;
         }
-        if (counterHashCode != null) {
-            count ++;
-        }
         if (random != null) {
             count ++;
         }
@@ -196,7 +193,7 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
     public Map<Charset, CharsetEncoder> charsetEncoderCache() {
         Map<Charset, CharsetEncoder> cache = charsetEncoderCache;
         if (cache == null) {
-            charsetEncoderCache = cache = new IdentityHashMap<Charset, CharsetEncoder>();
+            charsetEncoderCache = cache = new IdentityHashMap<>();
         }
         return cache;
     }
@@ -204,7 +201,7 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
     public Map<Charset, CharsetDecoder> charsetDecoderCache() {
         Map<Charset, CharsetDecoder> cache = charsetDecoderCache;
         if (cache == null) {
-            charsetDecoderCache = cache = new IdentityHashMap<Charset, CharsetDecoder>();
+            charsetDecoderCache = cache = new IdentityHashMap<>();
         }
         return cache;
     }
@@ -217,7 +214,7 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
     public <E> ArrayList<E> arrayList(int minCapacity) {
         ArrayList<E> list = (ArrayList<E>) arrayList;
         if (list == null) {
-            arrayList = new ArrayList<Object>(minCapacity);
+            arrayList = new ArrayList<>(minCapacity);
             return (ArrayList<E>) arrayList;
         }
         list.clear();
@@ -244,7 +241,7 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
     public Map<Class<?>, TypeParameterMatcher> typeParameterMatcherGetCache() {
         Map<Class<?>, TypeParameterMatcher> cache = typeParameterMatcherGetCache;
         if (cache == null) {
-            typeParameterMatcherGetCache = cache = new IdentityHashMap<Class<?>, TypeParameterMatcher>();
+            typeParameterMatcherGetCache = cache = new IdentityHashMap<>();
         }
         return cache;
     }
@@ -252,26 +249,16 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
     public Map<Class<?>, Map<String, TypeParameterMatcher>> typeParameterMatcherFindCache() {
         Map<Class<?>, Map<String, TypeParameterMatcher>> cache = typeParameterMatcherFindCache;
         if (cache == null) {
-            typeParameterMatcherFindCache = cache = new IdentityHashMap<Class<?>, Map<String, TypeParameterMatcher>>();
+            typeParameterMatcherFindCache = cache = new IdentityHashMap<>();
         }
         return cache;
     }
 
-    @Deprecated
-    public IntegerHolder counterHashCode() {
-        return counterHashCode;
-    }
-
-    @Deprecated
-    public void setCounterHashCode(IntegerHolder counterHashCode) {
-        this.counterHashCode = counterHashCode;
-    }
-
     public Map<Class<?>, Boolean> handlerSharableCache() {
         Map<Class<?>, Boolean> cache = handlerSharableCache;
         if (cache == null) {
             // Start with small capacity to keep memory overhead as low as possible.
-            handlerSharableCache = cache = new WeakHashMap<Class<?>, Boolean>(4);
+            handlerSharableCache = cache = new WeakHashMap<>(4);
         }
         return cache;
     }

common/src/main/java/io/netty/util/internal/UnpaddedInternalThreadLocalMap.java

@@ -32,7 +32,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  */
 class UnpaddedInternalThreadLocalMap {
 
-    static final ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = new ThreadLocal<InternalThreadLocalMap>();
+    static final ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = new ThreadLocal<>();
     static final AtomicInteger nextIndex = new AtomicInteger();
 
     /** Used by {@link FastThreadLocal} */
@@ -42,7 +42,6 @@ class UnpaddedInternalThreadLocalMap {
     int futureListenerStackDepth;
     int localChannelReaderStackDepth;
     Map<Class<?>, Boolean> handlerSharableCache;
-    IntegerHolder counterHashCode;
     ThreadLocalRandom random;
     Map<Class<?>, TypeParameterMatcher> typeParameterMatcherGetCache;
     Map<Class<?>, Map<String, TypeParameterMatcher>> typeParameterMatcherFindCache;