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8186958: Need method to create pre-sized HashMap

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Reviewed-by: chegar, naoto, joehw, lancea, wetmore, smarks
This commit is contained in:
XenoAmess 2022-04-19 00:03:56 +00:00 • committed by Stuart Marks
parent 41fc078323
commit 87faa85c59
30 changed files with 208 additions and 73 deletions
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38
src/java.base/share/classes/java/util/HashMap.java
View file

@ -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 @@ public class HashMap<K,V> extends AbstractMap<K,V>
* 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 class HashMap<K,V> extends AbstractMap<K,V>
* 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 @@ public class HashMap<K,V> extends AbstractMap<K,V>
}
}
/**
* 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));
}
}

4
src/java.base/share/classes/java/util/HashSet.java
View file

@ -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
@ -117,7 +117,7 @@ public class HashSet<E>
* @throws NullPointerException if the specified collection is null
*/
public HashSet(Collection<? extends E> c) {
map = new HashMap<>(Math.max((int) (c.size()/.75f) + 1, 16));
map = HashMap.newHashMap(Math.max(c.size(), 12));
addAll(c);
}

26
src/java.base/share/classes/java/util/LinkedHashMap.java
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 1997, 2020, 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
@ -339,6 +339,10 @@ public class LinkedHashMap<K,V>
* Constructs an empty insertion-ordered {@code LinkedHashMap} instance
* with the specified initial capacity and load factor.
*
* @apiNote
* To create a {@code LinkedHashMap} with an initial capacity that accommodates
* an expected number of mappings, use {@link #newLinkedHashMap(int) newLinkedHashMap}.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @throws IllegalArgumentException if the initial capacity is negative
@ -353,6 +357,10 @@ public class LinkedHashMap<K,V>
* Constructs an empty insertion-ordered {@code LinkedHashMap} instance
* with the specified initial capacity and a default load factor (0.75).
*
* @apiNote
* To create a {@code LinkedHashMap} with an initial capacity that accommodates
* an expected number of mappings, use {@link #newLinkedHashMap(int) newLinkedHashMap}.
*
* @param initialCapacity the initial capacity
* @throws IllegalArgumentException if the initial capacity is negative
*/
@ -788,5 +796,21 @@ public class LinkedHashMap<K,V>
public final Map.Entry<K,V> next() { return nextNode(); }
}
/**
* Creates a new, empty, insertion-ordered LinkedHashMap 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> LinkedHashMap<K, V> newLinkedHashMap(int numMappings) {
return new LinkedHashMap<>(HashMap.calculateHashMapCapacity(numMappings));
}
}

4
src/java.base/share/classes/java/util/ListResourceBundle.java
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1996, 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
@ -193,7 +193,7 @@ public abstract class ListResourceBundle extends ResourceBundle {
return;
Object[][] contents = getContents();
HashMap<String,Object> temp = new HashMap<>(contents.length);
HashMap<String,Object> temp = HashMap.newHashMap(contents.length);
for (Object[] content : contents) {
// key must be non-null String, value must be non-null
String key = (String) content[0];

27
src/java.base/share/classes/java/util/WeakHashMap.java
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1998, 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
@ -198,6 +198,10 @@ public class WeakHashMap<K,V>
* Constructs a new, empty {@code WeakHashMap} with the given initial
* capacity and the given load factor.
*
* @apiNote
* To create a {@code WeakHashMap} with an initial capacity that accommodates
* an expected number of mappings, use {@link #newWeakHashMap(int) newWeakHashMap}.
*
* @param initialCapacity The initial capacity of the {@code WeakHashMap}
* @param loadFactor The load factor of the {@code WeakHashMap}
* @throws IllegalArgumentException if the initial capacity is negative,
@ -223,6 +227,10 @@ public class WeakHashMap<K,V>
* Constructs a new, empty {@code WeakHashMap} with the given initial
* capacity and the default load factor (0.75).
*
* @apiNote
* To create a {@code WeakHashMap} with an initial capacity that accommodates
* an expected number of mappings, use {@link #newWeakHashMap(int) newWeakHashMap}.
*
* @param initialCapacity The initial capacity of the {@code WeakHashMap}
* @throws IllegalArgumentException if the initial capacity is negative
*/
@ -1335,4 +1343,21 @@ public class WeakHashMap<K,V>
}
}
/**
* Creates a new, empty WeakHashMap 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> WeakHashMap<K, V> newWeakHashMap(int numMappings) {
return new WeakHashMap<>(HashMap.calculateHashMapCapacity(numMappings));
}
}

6
src/java.base/share/classes/java/util/jar/Attributes.java
View file

@ -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
@ -69,7 +69,7 @@ public class Attributes implements Map<Object,Object>, Cloneable {
* Constructs a new, empty Attributes object with default size.
*/
public Attributes() {
this(11);
this(16);
}
/**
@ -79,7 +79,7 @@ public class Attributes implements Map<Object,Object>, Cloneable {
* @param size the initial number of attributes
*/
public Attributes(int size) {
map = new LinkedHashMap<>(size);
map = LinkedHashMap.newLinkedHashMap(size);
}
/**

2
src/java.base/share/classes/java/util/jar/JarVerifier.java
View file

@ -672,7 +672,7 @@ class JarVerifier {
* only about the asserted signatures. Verification of
* signature validity happens via the JarEntry apis.
*/
signerMap = new HashMap<>(verifiedSigners.size() + sigFileSigners.size());
signerMap = HashMap.newHashMap(verifiedSigners.size() + sigFileSigners.size());
signerMap.putAll(verifiedSigners);
signerMap.putAll(sigFileSigners);
}