8186958: Need method to create pre-sized HashMap

Reviewed-by: chegar, naoto, joehw, lancea, wetmore, smarks

Author: XenoAmess

src/java.base/macosx/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2022, 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
@@ -570,7 +570,7 @@ public Map<String, Integer> getDisplayNames(String calendarType,
                 String[] names = getCalendarDisplayStrings(locale.toLanguageTag(),
                         field, style);
                 if (names != null) {
-                    map = new HashMap<>((int)Math.ceil(names.length / 0.75));
+                    map = HashMap.newHashMap(names.length);
                     for (int value = 0; value < names.length; value++) {
                         if (names[value] != null) {
                             map.put(names[value], value);

src/java.base/share/classes/java/lang/Character.java

@@ -744,8 +744,7 @@ public static final class UnicodeBlock extends Subset {
          * 0.75 - the default load factor of HashMap
          */
         private static final int NUM_ENTITIES = 737;
-        private static Map<String, UnicodeBlock> map =
-                new HashMap<>((int)(NUM_ENTITIES / 0.75f + 1.0f));
+        private static Map<String, UnicodeBlock> map = HashMap.newHashMap(NUM_ENTITIES);
 
         /**
          * Creates a UnicodeBlock with the given identifier name.
@@ -8572,7 +8571,7 @@ public static enum UnicodeScript {
 
         private static final HashMap<String, Character.UnicodeScript> aliases;
         static {
-            aliases = new HashMap<>((int)(162 / 0.75f + 1.0f));
+            aliases = HashMap.newHashMap(162);
             aliases.put("ADLM", ADLAM);
             aliases.put("AGHB", CAUCASIAN_ALBANIAN);
             aliases.put("AHOM", AHOM);

src/java.base/share/classes/java/lang/Class.java

@@ -3910,7 +3910,7 @@ Map<String, T> enumConstantDirectory() {
             if (universe == null)
                 throw new IllegalArgumentException(
                     getName() + " is not an enum class");
-            directory = new HashMap<>((int)(universe.length / 0.75f) + 1);
+            directory = HashMap.newHashMap(universe.length);
             for (T constant : universe) {
                 directory.put(((Enum<?>)constant).name(), constant);
             }
@@ -4125,10 +4125,10 @@ private AnnotationData createAnnotationData(int classRedefinedCount) {
                 Class<? extends Annotation> annotationClass = e.getKey();
                 if (AnnotationType.getInstance(annotationClass).isInherited()) {
                     if (annotations == null) { // lazy construction
-                        annotations = new LinkedHashMap<>((Math.max(
+                        annotations = LinkedHashMap.newLinkedHashMap(Math.max(
                                 declaredAnnotations.size(),
                                 Math.min(12, declaredAnnotations.size() + superAnnotations.size())
-                            ) * 4 + 2) / 3
+                            )
                         );
                     }
                     annotations.put(annotationClass, e.getValue());

src/java.base/share/classes/java/lang/Module.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2022, 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
@@ -980,7 +980,7 @@ void implAddOpensToAllUnnamed(Set<String> concealedPkgs, Set<String> exportedPkg
         // the packages to all unnamed modules.
         Map<String, Set<Module>> openPackages = this.openPackages;
         if (openPackages == null) {
-            openPackages = new HashMap<>((4 * (concealedPkgs.size() + exportedPkgs.size()) / 3) + 1);
+            openPackages = HashMap.newHashMap(concealedPkgs.size() + exportedPkgs.size());
         } else {
             openPackages = new HashMap<>(openPackages);
         }
@@ -1133,8 +1133,7 @@ static Map<String, Module> defineModules(Configuration cf,
         boolean isBootLayer = (ModuleLayer.boot() == null);
 
         int numModules = cf.modules().size();
-        int cap = (int)(numModules / 0.75f + 1.0f);
-        Map<String, Module> nameToModule = new HashMap<>(cap);
+        Map<String, Module> nameToModule = HashMap.newHashMap(numModules);
 
         // to avoid repeated lookups and reduce iteration overhead, we create
         // arrays holding correlated information about each module.

src/java.base/share/classes/java/lang/Thread.java

@@ -1655,7 +1655,7 @@ public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
         // Get a snapshot of the list of all threads
         Thread[] threads = getThreads();
         StackTraceElement[][] traces = dumpThreads(threads);
-        Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
+        Map<Thread, StackTraceElement[]> m = HashMap.newHashMap(threads.length);
         for (int i = 0; i < threads.length; i++) {
             StackTraceElement[] stackTrace = traces[i];
             if (stackTrace != null) {

src/java.base/share/classes/java/lang/invoke/MethodHandleImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2022, 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
@@ -290,7 +290,7 @@ static MethodHandle makePairwiseConvertByEditor(MethodHandle target, MethodType
         BoundMethodHandle mh = target.rebind();
 
         // Match each unique conversion to the positions at which it is to be applied
-        var convSpecMap = new HashMap<Object, int[]>(((4 * convCount) / 3) + 1);
+        HashMap<Object, int[]> convSpecMap = HashMap.newHashMap(convCount);
         for (int i = 0; i < convSpecs.length - MH_RECEIVER_OFFSET; i++) {
             Object convSpec = convSpecs[i];
             if (convSpec == null) continue;

src/java.base/share/classes/java/lang/module/Resolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2022, 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
@@ -498,12 +498,11 @@ private void checkHashes() {
      */
     private Map<ResolvedModule, Set<ResolvedModule>> makeGraph(Configuration cf) {
 
-        // initial capacity of maps to avoid resizing
-        int capacity = 1 + (4 * nameToReference.size())/ 3;
+        int moduleCount = nameToReference.size();
 
         // the "reads" graph starts as a module dependence graph and
         // is iteratively updated to be the readability graph
-        Map<ResolvedModule, Set<ResolvedModule>> g1 = new HashMap<>(capacity);
+        Map<ResolvedModule, Set<ResolvedModule>> g1 = HashMap.newHashMap(moduleCount);
 
         // the "requires transitive" graph, contains requires transitive edges only
         Map<ResolvedModule, Set<ResolvedModule>> g2;
@@ -512,7 +511,7 @@ private Map<ResolvedModule, Set<ResolvedModule>> makeGraph(Configuration cf) {
         // as there may be selected modules that have a dependency on modules in
         // the parent configuration.
         if (ModuleLayer.boot() == null) {
-            g2 = new HashMap<>(capacity);
+            g2 = HashMap.newHashMap(moduleCount);
         } else {
             g2 = parents.stream()
                 .flatMap(Configuration::configurations)
@@ -539,7 +538,7 @@ private Map<ResolvedModule, Set<ResolvedModule>> makeGraph(Configuration cf) {
 
         // populate g1 and g2 with the dependences from the selected modules
 
-        Map<String, ResolvedModule> nameToResolved = new HashMap<>(capacity);
+        Map<String, ResolvedModule> nameToResolved = HashMap.newHashMap(moduleCount);
 
         for (ModuleReference mref : nameToReference.values()) {
             ModuleDescriptor descriptor = mref.descriptor();

src/java.base/share/classes/java/security/cert/CertificateRevokedException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2022, 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
@@ -245,7 +245,7 @@ private void readObject(ObjectInputStream ois)
         } else if (size < 0) {
             throw new IOException("size cannot be negative");
         } else {
-            extensions = new HashMap<>(size > 20 ? 20 : size);
+            extensions = HashMap.newHashMap(size > 20 ? 20 : size);
         }
 
         // Read in the extensions and put the mappings in the extensions map

src/java.base/share/classes/java/security/cert/PKIXRevocationChecker.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2022, 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
@@ -197,7 +197,7 @@ public void setOcspResponses(Map<X509Certificate, byte[]> responses)
         if (responses == null) {
             this.ocspResponses = Collections.<X509Certificate, byte[]>emptyMap();
         } else {
-            Map<X509Certificate, byte[]> copy = new HashMap<>(responses.size());
+            Map<X509Certificate, byte[]> copy = HashMap.newHashMap(responses.size());
             for (Map.Entry<X509Certificate, byte[]> e : responses.entrySet()) {
                 copy.put(e.getKey(), e.getValue().clone());
             }
@@ -216,7 +216,7 @@ public void setOcspResponses(Map<X509Certificate, byte[]> responses)
      *        Returns an empty map if no responses have been specified.
      */
     public Map<X509Certificate, byte[]> getOcspResponses() {
-        Map<X509Certificate, byte[]> copy = new HashMap<>(ocspResponses.size());
+        Map<X509Certificate, byte[]> copy = HashMap.newHashMap(ocspResponses.size());
         for (Map.Entry<X509Certificate, byte[]> e : ocspResponses.entrySet()) {
             copy.put(e.getKey(), e.getValue().clone());
         }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2022, 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
@@ -433,6 +433,10 @@ static final int tableSizeFor(int cap) {
      * Constructs an empty {@code HashMap} with the specified initial
      * capacity and load factor.
      *
+     * @apiNote
+     * To create a {@code HashMap} with an initial capacity that accommodates
+     * an expected number of mappings, use {@link #newHashMap(int) newHashMap}.
+     *
      * @param  initialCapacity the initial capacity
      * @param  loadFactor      the load factor
      * @throws IllegalArgumentException if the initial capacity is negative
@@ -455,6 +459,10 @@ public HashMap(int initialCapacity, float loadFactor) {
      * Constructs an empty {@code HashMap} with the specified initial
      * capacity and the default load factor (0.75).
      *
+     * @apiNote
+     * To create a {@code HashMap} with an initial capacity that accommodates
+     * an expected number of mappings, use {@link #newHashMap(int) newHashMap}.
+     *
      * @param  initialCapacity the initial capacity.
      * @throws IllegalArgumentException if the initial capacity is negative.
      */
@@ -2545,4 +2553,32 @@ static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
         }
     }
 
+    /**
+     * Calculate initial capacity for HashMap based classes, from expected size and default load factor (0.75).
+     *
+     * @param numMappings the expected number of mappings
+     * @return initial capacity for HashMap based classes.
+     * @since 19
+     */
+    static int calculateHashMapCapacity(int numMappings) {
+        return (int) Math.ceil(numMappings / (double) DEFAULT_LOAD_FACTOR);
+    }
+
+    /**
+     * Creates a new, empty HashMap suitable for the expected number of mappings.
+     * The returned map uses the default load factor of 0.75, and its initial capacity is
+     * generally large enough so that the expected number of mappings can be added
+     * without resizing the map.
+     *
+     * @param numMappings the expected number of mappings
+     * @param <K>         the type of keys maintained by this map
+     * @param <V>         the type of mapped values
+     * @return the newly created map
+     * @throws IllegalArgumentException if numMappings is negative
+     * @since 19
+     */
+    public static <K, V> HashMap<K, V> newHashMap(int numMappings) {
+        return new HashMap<>(calculateHashMapCapacity(numMappings));
+    }
+
 }