8263561: Re-examine uses of LinkedList

Reviewed-by: redestad

src/java.base/share/classes/java/lang/reflect/ProxyGenerator.java

@@ -41,7 +41,6 @@
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Map;
@@ -245,7 +244,7 @@ private static void checkReturnTypes(List<ProxyMethod> methods) {
          * List of return types that are not yet known to be
          * assignable from ("covered" by) any of the others.
          */
-        LinkedList<Class<?>> uncoveredReturnTypes = new LinkedList<>();
+        List<Class<?>> uncoveredReturnTypes = new ArrayList<>(1);
 
         nextNewReturnType:
         for (ProxyMethod pm : methods) {

src/java.base/share/classes/java/util/ResourceBundle.java

@@ -2888,7 +2888,7 @@ protected List<Locale> createObject(BaseLocale base) {
                 if (language.equals("nb") || isNorwegianBokmal) {
                     List<Locale> tmpList = getDefaultList("nb", script, region, variant);
                     // Insert a locale replacing "nb" with "no" for every list entry with precedence
-                    List<Locale> bokmalList = new LinkedList<>();
+                    List<Locale> bokmalList = new ArrayList<>();
                     for (Locale l_nb : tmpList) {
                         var isRoot = l_nb.getLanguage().isEmpty();
                         var l_no = Locale.getInstance(isRoot ? "" : "no",
@@ -2928,15 +2928,15 @@ private static List<Locale> getDefaultList(String language, String script, Strin
                 List<String> variants = null;
 
                 if (!variant.isEmpty()) {
-                    variants = new LinkedList<>();
+                    variants = new ArrayList<>();
                     int idx = variant.length();
                     while (idx != -1) {
                         variants.add(variant.substring(0, idx));
                         idx = variant.lastIndexOf('_', --idx);
                     }
                 }
 
-                List<Locale> list = new LinkedList<>();
+                List<Locale> list = new ArrayList<>();
 
                 if (variants != null) {
                     for (String v : variants) {

src/java.base/share/classes/jdk/internal/loader/URLClassPath.java

@@ -54,7 +54,6 @@
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.NoSuchElementException;
 import java.util.Properties;
@@ -219,7 +218,7 @@ public synchronized List<IOException> closeLoaders() {
         if (closed) {
             return Collections.emptyList();
         }
-        List<IOException> result = new LinkedList<>();
+        List<IOException> result = new ArrayList<>();
         for (Loader loader : loaders) {
             try {
                 loader.close();
@@ -961,7 +960,7 @@ Resource getResource(final String name, boolean check,
             Resource res;
             String[] jarFiles;
             int count = 0;
-            LinkedList<String> jarFilesList = null;
+            List<String> jarFilesList;
 
             /* If there no jar files in the index that can potential contain
              * this resource then return immediately.

src/java.base/share/classes/jdk/internal/util/jar/JarIndex.java

@@ -52,13 +52,13 @@ public class JarIndex {
      * The hash map that maintains mappings from
      * package/classe/resource to jar file list(s)
      */
-    private HashMap<String,LinkedList<String>> indexMap;
+    private final HashMap<String, List<String>> indexMap;
 
     /**
      * The hash map that maintains mappings from
      * jar file to package/class/resource lists
      */
-    private HashMap<String,LinkedList<String>> jarMap;
+    private final HashMap<String, List<String>> jarMap;
 
     /*
      * An ordered list of jar file names.
@@ -132,13 +132,13 @@ public String[] getJarFiles() {
 
     /*
      * Add the key, value pair to the hashmap, the value will
-     * be put in a linked list which is created if necessary.
+     * be put in a list which is created if necessary.
      */
     private void addToList(String key, String value,
-                           HashMap<String,LinkedList<String>> t) {
-        LinkedList<String> list = t.get(key);
+                           HashMap<String, List<String>> t) {
+        List<String> list = t.get(key);
         if (list == null) {
-            list = new LinkedList<>();
+            list = new ArrayList<>(1);
             list.add(value);
             t.put(key, list);
         } else if (!list.contains(value)) {
@@ -151,8 +151,8 @@ private void addToList(String key, String value,
      *
      * @param fileName the key of the mapping
      */
-    public LinkedList<String> get(String fileName) {
-        LinkedList<String> jarFiles = null;
+    public List<String> get(String fileName) {
+        List<String> jarFiles;
         if ((jarFiles = indexMap.get(fileName)) == null) {
             /* try the package name again */
             int pos;
@@ -166,7 +166,7 @@ public LinkedList<String> get(String fileName) {
     /**
      * Add the mapping from the specified file to the specified
      * jar file. If there were no mapping for the package of the
-     * specified file before, a new linked list will be created,
+     * specified file before, a new list will be created,
      * the jar file is added to the list and a new mapping from
      * the package to the jar file list is added to the hashmap.
      * Otherwise, the jar file will be added to the end of the
@@ -261,7 +261,7 @@ public void write(OutputStream out) throws IOException {
                 /* print out the jar file name */
                 String jar = jarFiles[i];
                 bw.write(jar + "\n");
-                LinkedList<String> jarlist = jarMap.get(jar);
+                List<String> jarlist = jarMap.get(jar);
                 if (jarlist != null) {
                     Iterator<String> listitr = jarlist.iterator();
                     while(listitr.hasNext()) {
@@ -320,11 +320,11 @@ public void read(InputStream is) throws IOException {
      *
      */
     public void merge(JarIndex toIndex, String path) {
-        Iterator<Map.Entry<String,LinkedList<String>>> itr = indexMap.entrySet().iterator();
+        Iterator<Map.Entry<String, List<String>>> itr = indexMap.entrySet().iterator();
         while(itr.hasNext()) {
-            Map.Entry<String,LinkedList<String>> e = itr.next();
+            Map.Entry<String, List<String>> e = itr.next();
             String packageName = e.getKey();
-            LinkedList<String> from_list = e.getValue();
+            List<String> from_list = e.getValue();
             Iterator<String> listItr = from_list.iterator();
             while(listItr.hasNext()) {
                 String jarName = listItr.next();

src/java.base/share/classes/sun/nio/ch/MembershipRegistry.java

@@ -30,7 +30,7 @@
 import java.nio.channels.MembershipKey;
 import java.util.HashMap;
 import java.util.Iterator;
-import java.util.LinkedList;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
@@ -94,7 +94,7 @@ void add(MembershipKeyImpl key) {
             keys = groups.get(group);
         }
         if (keys == null) {
-            keys = new LinkedList<>();
+            keys = new ArrayList<>();
             groups.put(group, keys);
         }
         keys.add(key);

src/java.base/share/classes/sun/nio/fs/AbstractPoller.java

@@ -40,14 +40,14 @@
 
 abstract class AbstractPoller implements Runnable {
 
-    // list of requests pending to the poller thread
-    private final LinkedList<Request> requestList;
+    // requests pending to the poller thread
+    private final ArrayDeque<Request> requests;
 
     // set to true when shutdown
     private boolean shutdown;
 
     protected AbstractPoller() {
-        this.requestList = new LinkedList<>();
+        this.requests = new ArrayDeque<>();
         this.shutdown = false;
     }
 
@@ -216,11 +216,11 @@ Object awaitResult() {
     private Object invoke(RequestType type, Object... params) throws IOException {
         // submit request
         Request req = new Request(type, params);
-        synchronized (requestList) {
+        synchronized (requests) {
             if (shutdown) {
                 throw new ClosedWatchServiceException();
             }
-            requestList.add(req);
+            requests.add(req);
 
             // wakeup thread
             wakeup();
@@ -243,9 +243,9 @@ private Object invoke(RequestType type, Object... params) throws IOException {
      */
     @SuppressWarnings("unchecked")
     boolean processRequests() {
-        synchronized (requestList) {
+        synchronized (requests) {
             Request req;
-            while ((req = requestList.poll()) != null) {
+            while ((req = requests.poll()) != null) {
                 // if in process of shutdown then reject request
                 if (shutdown) {
                     req.release(new ClosedWatchServiceException());

src/java.base/share/classes/sun/util/locale/provider/TimeZoneNameUtility.java

@@ -26,7 +26,7 @@
 package sun.util.locale.provider;
 
 import java.lang.ref.SoftReference;
-import java.util.LinkedList;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -98,7 +98,7 @@ private static String[][] loadZoneStrings(Locale locale) {
 
         // Performs per-ID retrieval.
         Set<String> zoneIDs = LocaleProviderAdapter.forJRE().getLocaleResources(locale).getZoneIDs();
-        List<String[]> zones = new LinkedList<>();
+        List<String[]> zones = new ArrayList<>();
         for (String key : zoneIDs) {
             String[] names = retrieveDisplayNamesImpl(key, locale);
             if (names != null) {

src/java.base/unix/classes/sun/net/dns/ResolverConfigurationImpl.java

@@ -26,7 +26,7 @@
 package sun.net.dns;
 
 import java.util.List;
-import java.util.LinkedList;
+import java.util.ArrayList;
 import java.util.StringTokenizer;
 import java.io.BufferedReader;
 import java.io.FileReader;
@@ -56,11 +56,11 @@ public class ResolverConfigurationImpl
     // Parse /etc/resolv.conf to get the values for a particular
     // keyword.
     //
-    private LinkedList<String> resolvconf(String keyword,
+    private ArrayList<String> resolvconf(String keyword,
                                           int maxperkeyword,
                                           int maxkeywords)
     {
-        LinkedList<String> ll = new LinkedList<>();
+        ArrayList<String> ll = new ArrayList<>();
 
         try {
             BufferedReader in =
@@ -111,8 +111,8 @@ private LinkedList<String> resolvconf(String keyword,
         return ll;
     }
 
-    private LinkedList<String> searchlist;
-    private LinkedList<String> nameservers;
+    private ArrayList<String> searchlist;
+    private ArrayList<String> nameservers;
 
 
     // Load DNS configuration from OS
@@ -133,7 +133,7 @@ private void loadConfig() {
         nameservers =
             java.security.AccessController.doPrivileged(
                 new java.security.PrivilegedAction<>() {
-                    public LinkedList<String> run() {
+                    public ArrayList<String> run() {
                         // typically MAXNS is 3 but we've picked 5 here
                         // to allow for additional servers if required.
                         return resolvconf("nameserver", 1, 5);
@@ -151,16 +151,16 @@ public LinkedList<String> run() {
     // obtain search list or local domain
 
     @SuppressWarnings("removal")
-    private LinkedList<String> getSearchList() {
+    private ArrayList<String> getSearchList() {
 
-        LinkedList<String> sl;
+        ArrayList<String> sl;
 
         // first try the search keyword in /etc/resolv.conf
 
         sl = java.security.AccessController.doPrivileged(
                  new java.security.PrivilegedAction<>() {
-                    public LinkedList<String> run() {
-                        LinkedList<String> ll;
+                    public ArrayList<String> run() {
+                        ArrayList<String> ll;
 
                         // first try search keyword (max 6 domains)
                         ll = resolvconf("search", 6, 1);
@@ -183,8 +183,8 @@ public LinkedList<String> run() {
 
         sl = java.security.AccessController.doPrivileged(
                  new java.security.PrivilegedAction<>() {
-                    public LinkedList<String> run() {
-                        LinkedList<String> ll;
+                    public ArrayList<String> run() {
+                        ArrayList<String> ll;
 
                         ll = resolvconf("domain", 1, 1);
                         if (ll.size() > 0) {
@@ -201,7 +201,7 @@ public LinkedList<String> run() {
         // no local domain so try fallback (RPC) domain or
         // hostName
 
-        sl = new LinkedList<>();
+        sl = new ArrayList<>();
         String domain = fallbackDomain0();
         if (domain != null && !domain.isEmpty()) {
             sl.add(domain);

test/jdk/sun/misc/JarIndex/JarIndexMergeTest.java

@@ -35,7 +35,7 @@
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
-import java.util.LinkedList;
+import java.util.List;
 import java.util.jar.JarEntry;
 import java.util.jar.JarOutputStream;
 // implementation specific API
@@ -64,7 +64,7 @@ public static void main(String[] args) throws Exception {
     static void assertFileResolved(JarIndex jarIndex2, String file,
                                    String jarName) {
         @SuppressWarnings("unchecked")
-        LinkedList<String> jarLists = (LinkedList<String>)jarIndex2.get(file);
+        List<String> jarLists = (List<String>)jarIndex2.get(file);
         if (jarLists == null || jarLists.size() == 0 ||
             !jarName.equals(jarLists.get(0))) {
             throw new RuntimeException(