From 7362c4ce603d81f276a83070e51bda52c3528bd7 Mon Sep 17 00:00:00 2001
From: Dawid Weiss <dawid.weiss@carrotsearch.com>
Date: Mon, 12 Oct 2020 09:15:07 +0200
Subject: [PATCH] LUCENE-6831: start removing LinkedList in favor of ArrayList
 or De/Queues (#1969)

I'm committing it in, seems like a trivial thing.
---
 .gitignore                                                   | 3 +++
 .../org/apache/lucene/index/DocumentsWriterFlushQueue.java   | 4 ++--
 .../core/src/java/org/apache/lucene/index/IndexWriter.java   | 5 +++--
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/.gitignore b/.gitignore
index f120ec44aaa..31976196383 100644
--- a/.gitignore
+++ b/.gitignore
@@ -37,3 +37,6 @@ build/
 
 # Ignore the generated local settings file.
 gradle.properties
+
+# IntelliJ creates this folder, ignore.
+dev-tools/missing-doclet/out/
diff --git a/lucene/core/src/java/org/apache/lucene/index/DocumentsWriterFlushQueue.java b/lucene/core/src/java/org/apache/lucene/index/DocumentsWriterFlushQueue.java
index 132b496bcfc..b5d8d3de810 100644
--- a/lucene/core/src/java/org/apache/lucene/index/DocumentsWriterFlushQueue.java
+++ b/lucene/core/src/java/org/apache/lucene/index/DocumentsWriterFlushQueue.java
@@ -17,7 +17,7 @@
 package org.apache.lucene.index;
 
 import java.io.IOException;
-import java.util.LinkedList;
+import java.util.ArrayDeque;
 import java.util.Queue;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.locks.ReentrantLock;
@@ -29,7 +29,7 @@ import org.apache.lucene.util.IOUtils;
  * @lucene.internal 
  */
 final class DocumentsWriterFlushQueue {
-  private final Queue<FlushTicket> queue = new LinkedList<>();
+  private final Queue<FlushTicket> queue = new ArrayDeque<>();
   // we track tickets separately since count must be present even before the ticket is
   // constructed ie. queue.size would not reflect it.
   private final AtomicInteger ticketCount = new AtomicInteger();
diff --git a/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java b/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
index 7cc907af897..b1a53464aba 100644
--- a/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
@@ -18,14 +18,15 @@ package org.apache.lucene.index;
 
 import java.io.Closeable;
 import java.io.IOException;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.Deque;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -399,7 +400,7 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable,
   private final HashSet<SegmentCommitInfo> mergingSegments = new HashSet<>();
   private final MergeScheduler mergeScheduler;
   private final Set<SegmentMerger> runningAddIndexesMerges = new HashSet<>();
-  private final LinkedList<MergePolicy.OneMerge> pendingMerges = new LinkedList<>();
+  private final Deque<MergePolicy.OneMerge> pendingMerges = new ArrayDeque<>();
   private final Set<MergePolicy.OneMerge> runningMerges = new HashSet<>();
   private final List<MergePolicy.OneMerge> mergeExceptions = new ArrayList<>();
   private long mergeGen;