Completed work for Issue #916

Removed ```Lucene.Net.Support.Arrays.Empty<T>()``` and ```FEATURE_ARRAYEMPTY```.
Converted all ```Arrays.Empty<T>()``` to ```Array.Empty<T>()``` and added ```using System;``` where required.
Removed ```using Lucene.Net.Support;``` statements that were no longer required.

src/Lucene.Net.Analysis.Common/Analysis/CharFilter/BaseCharFilter.cs

@@ -1,7 +1,6 @@
 // Lucene version compatibility level 4.8.1
 using J2N.Numerics;
 using Lucene.Net.Diagnostics;
-using Lucene.Net.Support;
 using Lucene.Net.Util;
 using System.Diagnostics;
 using System.IO;
@@ -129,4 +128,4 @@ protected virtual void AddOffCorrectMap(int off, int cumulativeDiff)
             }
         }
     }
-}
+}

src/Lucene.Net.Analysis.Common/Analysis/Hunspell/Dictionary.cs

@@ -44,7 +44,7 @@ namespace Lucene.Net.Analysis.Hunspell
     /// </summary>
     public class Dictionary
     {
-        private static readonly char[] NOFLAGS = Arrays.Empty<char>();
+        private static readonly char[] NOFLAGS = Array.Empty<char>();
 
         private const string ALIAS_KEY = "AF";
         private const string MORPH_ALIAS_KEY = "AM";
@@ -153,7 +153,7 @@ public class Dictionary
         /// <param name="dictionary"> <see cref="Stream"/> for reading the hunspell dictionary file (won't be disposed). </param>
         /// <exception cref="IOException"> Can be thrown while reading from the <see cref="Stream"/>s </exception>
         /// <exception cref="Exception"> Can be thrown if the content of the files does not meet expected formats </exception>
-        public Dictionary(Stream affix, Stream dictionary) 
+        public Dictionary(Stream affix, Stream dictionary)
             : this(affix, new JCG.List<Stream>() { dictionary }, false)
         {
         }
@@ -752,12 +752,12 @@ private static Encoding GetSystemEncoding(string encoding) // LUCENENET: CA1822:
             }
             // .NET doesn't recognize the encoding without a dash between ISO and the number
             // https://msdn.microsoft.com/en-us/library/system.text.encodinginfo.getencoding(v=vs.110).aspx
-            if (encoding.Length > 3 && encoding.StartsWith("ISO", StringComparison.OrdinalIgnoreCase) && 
+            if (encoding.Length > 3 && encoding.StartsWith("ISO", StringComparison.OrdinalIgnoreCase) &&
                 encoding[3] != '-')
             {
                 encoding = "iso-" + encoding.Substring(3);
             }
-            // Special case - for codepage 1250-1258, we need to change to 
+            // Special case - for codepage 1250-1258, we need to change to
             // windows-1251, etc.
             else if (windowsCodePagePattern.IsMatch(encoding))
             {
@@ -1285,7 +1285,7 @@ internal override char[] ParseFlags(string rawFlags)
 
                 for (int i = 0; i < rawFlagParts.Length; i++)
                 {
-                    // note, removing the trailing X/leading I for nepali... what is the rule here?! 
+                    // note, removing the trailing X/leading I for nepali... what is the rule here?!
                     string replacement = leadingDigitPattern.Replace(rawFlagParts[i], "");
                     // note, ignoring empty flags (this happens in danish, for example)
                     if (replacement.Length == 0)
@@ -1313,7 +1313,7 @@ internal override char[] ParseFlags(string rawFlags)
             {
                 if (rawFlags.Length == 0)
                 {
-                    return Arrays.Empty<char>(); // LUCENENET: Optimized char[] creation
+                    return Array.Empty<char>(); // LUCENENET: Optimized char[] creation
                 }
 
                 StringBuilder builder = new StringBuilder();
@@ -1458,4 +1458,4 @@ internal static void ApplyMappings(FST<CharsRef> fst, StringBuilder sb)
             }
         }
     }
-}
+}

src/Lucene.Net.Analysis.Common/Analysis/Query/QueryAutoStopWordAnalyzer.cs

@@ -3,10 +3,10 @@
 using Lucene.Net.Analysis.Core;
 using Lucene.Net.Analysis.Util;
 using Lucene.Net.Index;
-using Lucene.Net.Support;
 using Lucene.Net.Util;
 using System.Collections.Generic;
 using System.IO;
+using System;
 using JCG = J2N.Collections.Generic;
 
 namespace Lucene.Net.Analysis.Query
@@ -30,11 +30,11 @@ namespace Lucene.Net.Analysis.Query
 
     /// <summary>
     /// An <see cref="Analyzer"/> used primarily at query time to wrap another analyzer and provide a layer of protection
-    /// which prevents very common words from being passed into queries. 
+    /// which prevents very common words from being passed into queries.
     /// <para>
     /// For very large indexes the cost
     /// of reading TermDocs for a very common word can be  high. This analyzer was created after experience with
-    /// a 38 million doc index which had a term in around 50% of docs and was causing TermQueries for 
+    /// a 38 million doc index which had a term in around 50% of docs and was causing TermQueries for
     /// this term to take 2 seconds.
     /// </para>
     /// </summary>
@@ -169,9 +169,9 @@ protected override TokenStreamComponents WrapComponents(string fieldName, TokenS
         ///                  method calls will be returned </param>
         /// <returns> the stop words identified for a field </returns>
         public string[] GetStopWords(string fieldName)
-        {            
+        {
             var stopWords = stopWordsPerField[fieldName];
-            return stopWords != null ? stopWords.ToArray() : Arrays.Empty<string>();
+            return stopWords != null ? stopWords.ToArray() : Array.Empty<string>();
         }
 
         /// <summary>
@@ -192,4 +192,4 @@ public Term[] GetStopWords()
             return allStopWords.ToArray();
         }
     }
-}
+}

src/Lucene.Net.Analysis.Common/Analysis/Shingle/ShingleFilter.cs

@@ -1,6 +1,5 @@
 // Lucene version compatibility level 4.8.1
 using Lucene.Net.Analysis.TokenAttributes;
-using Lucene.Net.Support;
 using Lucene.Net.Util;
 using System;
 using System.Collections.Generic;
@@ -29,12 +28,12 @@ namespace Lucene.Net.Analysis.Shingle
     /// <summary>
     /// <para>A <see cref="ShingleFilter"/> constructs shingles (token n-grams) from a token stream.
     /// In other words, it creates combinations of tokens as a single token.
-    /// 
+    ///
     /// </para>
     /// <para>For example, the sentence "please divide this sentence into shingles"
     /// might be tokenized into shingles "please divide", "divide this",
     /// "this sentence", "sentence into", and "into shingles".
-    /// 
+    ///
     /// </para>
     /// <para>This filter handles position increments > 1 by inserting filler tokens
     /// (tokens with termtext "_"). It does not handle a position increment of 0.
@@ -58,7 +57,7 @@ public sealed class ShingleFilter : TokenFilter
         public const int DEFAULT_MIN_SHINGLE_SIZE = 2;
 
         /// <summary>
-        /// default token type attribute value is "shingle" 
+        /// default token type attribute value is "shingle"
         /// </summary>
         public const string DEFAULT_TOKEN_TYPE = "shingle";
 
@@ -131,7 +130,7 @@ public sealed class ShingleFilter : TokenFilter
         /// <summary>
         /// When the next input stream token has a position increment greater than
         /// one, it is stored in this field until sufficient filler tokens have been
-        /// inserted to account for the position increment. 
+        /// inserted to account for the position increment.
         /// </summary>
         private AttributeSource nextInputStreamToken;
 
@@ -141,7 +140,7 @@ public sealed class ShingleFilter : TokenFilter
         private bool isNextInputStreamToken = false;
 
         /// <summary>
-        /// Whether at least one unigram or shingle has been output at the current 
+        /// Whether at least one unigram or shingle has been output at the current
         /// position.
         /// </summary>
         private bool isOutputHere = false;
@@ -244,7 +243,7 @@ public void SetOutputUnigrams(bool outputUnigrams)
         /// </para>
         /// <para>Note that if outputUnigrams==true, then unigrams are always output,
         /// regardless of whether any shingles are available.
-        /// 
+        ///
         /// </para>
         /// </summary>
         /// <param name="outputUnigramsIfNoShingles"> Whether or not to output a single
@@ -275,7 +274,7 @@ public void SetMaxShingleSize(int maxShingleSize)
         /// calling this method.
         /// </para>
         /// <para>The unigram output option is independent of the min shingle size.
-        /// 
+        ///
         /// </para>
         /// </summary>
         /// <param name="minShingleSize"> min size of output shingles </param>
@@ -308,7 +307,7 @@ public void SetTokenSeparator(string tokenSeparator)
         /// <param name="fillerToken"> string to insert at each position where there is no token </param>
         public void SetFillerToken(string fillerToken)
         {
-            this.fillerToken = null == fillerToken ? Arrays.Empty<char>() : fillerToken.ToCharArray();
+            this.fillerToken = null == fillerToken ? Array.Empty<char>() : fillerToken.ToCharArray();
         }
 
         public override bool IncrementToken()
@@ -434,7 +433,7 @@ private InputWindowToken GetNextToken(InputWindowToken target)
                     }
                     if (posIncrAtt.PositionIncrement > 1)
                     {
-                        // Each output shingle must contain at least one input token, 
+                        // Each output shingle must contain at least one input token,
                         // so no more than (maxShingleSize - 1) filler tokens will be inserted.
                         numFillerTokensToInsert = Math.Min(posIncrAtt.PositionIncrement - 1, maxShingleSize - 1);
                         // Save the current token as the next input stream token
@@ -499,7 +498,7 @@ public override void End()
         }
 
         /// <summary>
-        /// <para>Fills <see cref="inputWindow"/> with input stream tokens, if available, 
+        /// <para>Fills <see cref="inputWindow"/> with input stream tokens, if available,
         /// shifting to the right if the window was previously full.
         /// </para>
         /// <para>
@@ -577,7 +576,7 @@ public override void Reset()
         /// <para><code>gramSize</code> will take on values from the circular sequence
         /// <b>{ [ 1, ] <see cref="minShingleSize"/> [ , ... , <see cref="maxShingleSize"/> ] }</b>.
         /// </para>
-        /// <para>1 is included in the circular sequence only if 
+        /// <para>1 is included in the circular sequence only if
         /// <see cref="outputUnigrams"/> = true.
         /// </para>
         /// </summary>
@@ -606,7 +605,7 @@ public CircularSequence(ShingleFilter shingleFilter)
             /// <code>gramSize</code> will take on values from the circular sequence
             /// <b>{ [ 1, ] <see cref="minShingleSize"/> [ , ... , <see cref="maxShingleSize"/> ] }</b>.
             /// </para>
-            /// <para>1 is included in the circular sequence only if 
+            /// <para>1 is included in the circular sequence only if
             /// <see cref="outputUnigrams"/> = true.
             /// </para>
             /// </summary>
@@ -628,13 +627,13 @@ public virtual void Advance()
             }
 
             /// <summary>
-            /// <para>Sets this circular number's value to the first member of the 
+            /// <para>Sets this circular number's value to the first member of the
             /// circular sequence
             /// </para>
             /// <para><code>gramSize</code> will take on values from the circular sequence
             /// <b>{ [ 1, ] <see cref="minShingleSize"/> [ , ... , <see cref="maxShingleSize"/> ] }</b>.
             /// </para>
-            /// <para>1 is included in the circular sequence only if 
+            /// <para>1 is included in the circular sequence only if
             /// <see cref="outputUnigrams"/> = true.
             /// </para>
             /// </summary>
@@ -650,7 +649,7 @@ public void Reset()
             /// </para>
             /// <para>If <see cref="outputUnigrams"/> = true, the first member of the circular
             /// sequence will be 1; otherwise, it will be <see cref="minShingleSize"/>.
-            /// 
+            ///
             /// </para>
             /// </summary>
             /// <returns> true if the current value is the first member of the circular
@@ -685,4 +684,4 @@ public InputWindowToken(AttributeSource attSource)
             }
         }
     }
-}
+}