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src/jdk.compiler/share/classes/com/sun/tools/javac/api/JavacTaskPool.java

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rev 50962 : [mq]: 8206122-Use-Queue-in-place-of-ArrayList-when-need-to-remove-first-element

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this

@@ -25,14 +25,26 @@
 
 package com.sun.tools.javac.api;
 
 import java.io.PrintStream;
 import java.io.Writer;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+import javax.tools.Diagnostic;
+import javax.tools.DiagnosticListener;
+import javax.tools.JavaFileManager;
+import javax.tools.JavaFileObject;
 
 import com.sun.source.tree.ClassTree;
 import com.sun.source.tree.CompilationUnitTree;
 import com.sun.source.util.JavacTask;
 import com.sun.source.util.TaskEvent;

@@ -51,25 +63,12 @@
 import com.sun.tools.javac.comp.CompileStates;
 import com.sun.tools.javac.comp.Enter;
 import com.sun.tools.javac.comp.Modules;
 import com.sun.tools.javac.main.Arguments;
 import com.sun.tools.javac.main.JavaCompiler;
-import com.sun.tools.javac.tree.JCTree.JCClassDecl;
-
-import javax.tools.Diagnostic;
-import javax.tools.DiagnosticListener;
-import javax.tools.JavaFileManager;
-import javax.tools.JavaFileObject;
-
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.stream.Collectors;
-import java.util.stream.StreamSupport;
-
 import com.sun.tools.javac.model.JavacElements;
+import com.sun.tools.javac.tree.JCTree.JCClassDecl;
 import com.sun.tools.javac.util.Context;
 import com.sun.tools.javac.util.DefinedBy;
 import com.sun.tools.javac.util.DefinedBy.Api;
 import com.sun.tools.javac.util.Log;
 

@@ -99,13 +98,14 @@
  * deletion without notice.</b>
  */
 public class JavacTaskPool {
 
     private static final JavacTool systemProvider = JavacTool.create();
+    private static final Queue<ReusableContext> EMPTY_QUEUE = new ArrayDeque<>(0);
 
     private final int maxPoolSize;
-    private final Map<List<String>, List<ReusableContext>> options2Contexts = new HashMap<>();
+    private final Map<List<String>, Queue<ReusableContext>> options2Contexts = new HashMap<>();
     private int id;
 
     private int statReused = 0;
     private int statNew = 0;
     private int statPolluted = 0;

@@ -157,18 +157,18 @@
                              .collect(Collectors.toCollection(ArrayList::new));
 
         ReusableContext ctx;
 
         synchronized (this) {
-            List<ReusableContext> cached =
-                    options2Contexts.getOrDefault(opts, Collections.emptyList());
+            Queue<ReusableContext> cached =
+                    options2Contexts.getOrDefault(opts, EMPTY_QUEUE);
 
             if (cached.isEmpty()) {
                 ctx = new ReusableContext(opts);
                 statNew++;
             } else {
-                ctx = cached.remove(0);
+                ctx = cached.remove();
                 statReused++;
             }
         }
 
         ctx.useCount++;

@@ -198,11 +198,11 @@
                                             .findFirst()
                                             .get();
                     options2Contexts.get(toRemove.arguments).remove(toRemove);
                     statRemoved++;
                 }
-                options2Contexts.computeIfAbsent(ctx.arguments, x -> new ArrayList<>()).add(ctx);
+                options2Contexts.computeIfAbsent(ctx.arguments, x -> new ArrayDeque<>()).add(ctx);
                 ctx.timeStamp = id++;
             }
         }
 
         return result;
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