想深入了解一下ConcurrentHashMap源码的时候先阅读HashMap源码，整理如下
package app; import java.io.IOException; import java.io.InvalidObjectException; import java.io.Serializable; import java.util.AbstractCollection; import java.util.AbstractMap; import java.util.AbstractSet; import java.util.Arrays; import java.util.Collection; import java.util.ConcurrentModificationException; import java.util.Iterator; import java.util.Map; import java.util.NoSuchElementException; import java.util.Objects; import java.util.Set; public class HashMap<K,V> extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable { /* HashMap 的实例有两个参数影响其性能：初始容量 和加载因子。 容量是哈希表中桶的数量，初始容量只是哈希表在创建时的容量。 加载因子是哈希表在其容量自动增加之前可以达到多满的一种尺度。 当哈希表中的条目数超出了加载因子与当前容量的乘积时， 则要对该哈希表进行 rehash 操作（即重建内部数据结构）， 从而哈希表将具有大约两倍的桶数。 加载因子默认值为0.75，默认哈希表容量为16 */ // The default initial capacity - MUST be a power of two. // 默认HashMap的容量，初始化容量16 HashMap的容量必须是2的指数倍 【Hashtable是11】 static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16 // 最大容量2的30次方 。 // HashMap Bucket数组的长度,int 是4个字节存储， // 去掉其符号位数为31位，再考虑到这里其实是定义HashMap Bucket数组的长度，考虑到Java堆存储空间的限制，定位30位，其大小为107****24。 static final int MAXIMUM_CAPACITY = 1 << 30; // The load factor used when none specified in constructor. // 默认加载因子默认的平衡因子为0.75，权衡了时间复杂度与空间复杂度之后的最好取值（JDK说是最好的）， // 过高的因子会降低存储空间但是查找（lookup，包括HashMap中的put与get方法）的时间就会增加。 static final float DEFAULT_LOAD_FACTOR = 0.75f; // An empty table instance to share when the table is not inflated. // 空的Entry的二维数组,用来存储键值对的Entry数组,用于设置刚刚初始化的HashMap对象,用来减少存储空间 static final Entry<?,?>[] EMPTY_TABLE = {}; // transient 表明该数据不参与序列化？为什么用transient // 1.transient 首先是表明该数据不参与序列化。假设HashMap 中的存储数据的数组还有很多的空间没有被使用， // 没有被使用到的空间被序列化没有意义。所以下文会有手动使用 writeObject() 方法，只序列化实际存储元素的数组。 // 2. 不同的虚拟机对于相同 hashCode 产生的 Code 值可能是不一样的，如果使用默认序列化，则反序列化后，元素的位置和之前的是保持一致的， // 可是由于 hashCode 的值不一样了，那么后续看到的定位函数 indexOf（）返回的元素下标就会不同，其结果会出差错。 // The table, resized as necessary. Length MUST Always be a power of two. // **HashMap底层Bucket数组 transient Entry<K,V>[] table = (Entry<K,V>[]) EMPTY_TABLE; /** * The number of key-value mappings contained in this map. */ // 当前HashMap键值对K/V数据的大小 transient int size; // The next size value at which to resize (capacity * load factor). // If table == EMPTY_TABLE then this is the initial capacity at which the // table will be created when inflated. // 阀值（threshold = capacity * loadFactor ），当size超过threshold时，table将会扩容. int threshold; // The load factor for the hash table. // 负载因子 final float loadFactor; // Fail-Fast机制：java.util.HashMap非线程安全，如果在使用迭代器的过程中有其他线程修改了map，会抛出ConcurrentModificationException // 记录HashMap修改次数，如增、删元素或rehash。这个字段被用来当迭代器的fail-fast检查线程是否同步 transient int modCount; //默认的阀值 static final int ALTERNATIVE_HASHING_THRESHOLD_DEFAULT = Integer.MAX_VALUE; // Holder是为了加载获取threshold的配置参数。 private static class Holder { /** * Table capacity above which to switch to use alternative hashing. */ static final int ALTERNATIVE_HASHING_THRESHOLD; static { // JDK 1.7新加，针对字符串的key的hash算法会提供更好的hashcode分布减少冲突； // 如果想启用此特性，需设置jdk.map.althashing.threshold系统属性的值为一个非负数（默认是-1）这个值代表了一个集合大小的threshold， // 超过这个值，就会使用新的hash算法。需要注意的一点，只有当re-hash的时候，新的hash算法才会起作用。 String altThreshold = java.security.AccessController.doPrivileged(new sun.security.action.GetPropertyAction("jdk.map.althashing.threshold")); int threshold; try { threshold = (null != altThreshold) ? Integer.parseInt(altThreshold) : ALTERNATIVE_HASHING_THRESHOLD_DEFAULT; // disable alternative hashing if -1 if (threshold == -1) { threshold = Integer.MAX_VALUE; } if (threshold < 0) { throw new IllegalArgumentException("value must be positive integer."); } } catch(IllegalArgumentException failed) { throw new Error("Illegal value for 'jdk.map.althashing.threshold'", failed); } ALTERNATIVE_HASHING_THRESHOLD = threshold; } } // If 0 then alternative hashing is disabled. // 用于hash的种子 transient int hashSeed = 0; //构造函数：使用初始化容量和加载因子初始化HashMap public HashMap(int initialCapacity, float loadFactor) { if (initialCapacity < 0) throw new IllegalArgumentException("Illegal initial capacity: " + initialCapacity); if (initialCapacity > MAXIMUM_CAPACITY) initialCapacity = MAXIMUM_CAPACITY; if (loadFactor <= 0 || Float.isNaN(loadFactor)) throw new IllegalArgumentException("Illegal load factor: " + loadFactor); this.loadFactor = loadFactor; threshold = initialCapacity; // init() hook because : HashMap是可序列化的，而反序列化方法（readObject()）是一个跟构造器性质相似、但却不是构造器的奇怪的东西. // 为了让子类能方便规整地实现构造初始化与反序列初始化的功能，HashMap就在构造器末尾和反序列化方法末尾都埋了这个init()钩子， // 这样子类就不用为这两种不同的初始化需求而重复头疼了。 // jdk8 改名为reinitialize(), // LinkedHashMap要维持插入顺序，为此它会把所有插入的节点（键值对）用双向链表串在一起。而在它的init()实现里，它就创建并初始化了该双向链表的头节点。 init(); } // Constructs ,指定负载因子 public HashMap(int initialCapacity) { this(initialCapacity, DEFAULT_LOAD_FACTOR); } /** * Constructs 使用默认容量和加载因子初始化HashMap */ public HashMap() { this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR); } /** * Constructs a new <tt>HashMap</tt> with the same mappings as the * specified <tt>Map</tt>. The <tt>HashMap</tt> is created with * default load factor (0.75) and an initial capacity sufficient to * hold the mappings in the specified <tt>Map</tt>. * * @param m the map whose mappings are to be placed in this map * @throws NullPointerException if the specified map is null */ // 从一个已有的Map创建一个新的HashMap public HashMap(Map<? extends K, ? extends V> m) { this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1, DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR); inflateTable(threshold); putAllForCreate(m); } // 将number扩展成2的倍数 ,返回比入参初始容量大的最小的2的幂数 private static int roundUpToPowerOf2(int number) { // assert number >= 0 : "number must be non-negative"; int rounded = number >= MAXIMUM_CAPACITY ? MAXIMUM_CAPACITY : (rounded = Integer.highestOneBit(number)) != 0 ? (Integer.bitCount(number) > 1) ? rounded << 1 : rounded : 1; return rounded; } /** * 【JDK 1.7新加】Inflates the table. 扩充 HASHMAP 容量 */ private void inflateTable(int toSize) { // Find a power of 2 >= toSize int capacity = roundUpToPowerOf2(toSize); //重新设置阀值 threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1); table = new Entry[capacity]; initHashSeedAsNeeded(capacity); } /** * Initialization hook for subclasses. This method is called * in all constructors and pseudo-constructors (clone, readObject) * after HashMap has been initialized but before any entries have * been inserted. (In the absence of this method, readObject would * require explicit knowledge of subclasses.) */ // 内部使用,可作为一个钩子来被子类使用，它已经作为模版模式被所有的构造器，clone等调用。 void init() { } // Initialize the hashing mask value. We defer initialization until we really need it. final boolean initHashSeedAsNeeded(int capacity) { boolean currentAltHashing = hashSeed != 0; //根据系统函数得到一个hash boolean useAltHashing = sun.misc.VM.isBooted() && (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD); boolean switching = currentAltHashing ^ useAltHashing; //如果hashSeed初始化为0则跳过switching //否则使用系统函数得到新的hashSeed if (switching) { hashSeed = useAltHashing ? sun.misc.Hashing.randomHashSeed(this) : 0; } return switching; } /** * Retrieve object hash code and applies a supplemental hash function to the * result hash, which defends against poor quality hash functions. This is * critical because HashMap uses power-of-two length hash tables, that * otherwise encounter collisions for hashCodes that do not differ * in lower bits. Note: Null keys always map to hash 0, thus index 0. */ // 哈希算法的核心：哈希函数 ,用来计算对象的hash值 final int hash(Object k) { int h = hashSeed; //通过hashSeed初始化的值的不同来选择不同的hash方式 if (0 != h && k instanceof String) { //String类采用不同的hash函数 return sun.misc.Hashing.stringHash32((String) k); } h ^= k.hashCode(); // This function ensures that hashCodes that differ only by // constant multiples at each bit position have a bounded // number of collisions (approximately 8 at default load factor). h ^= (h >>> 20) ^ (h >>> 12); return h ^ (h >>> 7) ^ (h >>> 4); } // Returns index for hash code h. // 通过得到的hash值来确定返回hash code对应的length中的下标 static int indexFor(int h, int length) { // assert Integer.bitCount(length) == 1 : "length must be a non-zero power of 2"; return h & (length-1); } // 当前HashMap键值对K/V数据的大小 public int size() { return size; } // Returns <tt>true</tt> if this map contains no key-value mappings. public boolean isEmpty() { return size == 0; } public V get(Object key) { if (key == null) return getForNullKey(); Entry<K,V> entry = getEntry(key); return null == entry ? null : entry.getValue(); } private V getForNullKey() { if (size == 0) { return null; } for (Entry<K,V> e = table[0]; e != null; e = e.next) { if (e.key == null) return e.value; } return null; } public boolean containsKey(Object key) { return getEntry(key) != null; } // final Entry<K,V> getEntry(Object key) { if (size == 0) { return null; } //通过key的hash值确定table下标（null对应下标0） int hash = (key == null) ? 0 : hash(key); // 遍历table中的 entry数组 for (Entry<K,V> e = table[indexFor(hash, table.length)]; e != null; e = e.next) { Object k; // 因为存在不同的key对应相同的hash值，还要判读key是否一样 if ( e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k))) ) return e; } return null; } // // 通过key的hash值确定table下标，如果key已经存在则更新，不存在则调用addEntry方法 public V put(K key, V value) { if (table == EMPTY_TABLE) { inflateTable(threshold); } if (key == null) return putForNullKey(value); int hash = hash(key); int i = indexFor(hash, table.length); for (Entry<K,V> e = table[i]; e != null; e = e.next) { Object k; // 因为存在不同的key对应相同的hash值，还要判读key是否一样 if (e.hash == hash && ((k = e.key) == key || key.equals(k))) { V oldValue = e.value; e.value = value; e.recordAccess(this); return oldValue; // 如果已经存在，更新值 } } // //上面的循环结束表示当前的key不存在与表中，需要另外增加 modCount++; addEntry(hash, key, value, i); return null; } /** * Offloaded version of put for null keys */ private V putForNullKey(V value) { for (Entry<K,V> e = table[0]; e != null; e = e.next) { if (e.key == null) { V oldValue = e.value; e.value = value; e.recordAccess(this); return oldValue; } } modCount++; addEntry(0, null, value, 0); return null; } /** * This method is used instead of put by constructors and * pseudoconstructors (clone, readObject). It does not resize the table, * check for comodification, etc. It calls createEntry rather than * addEntry. */ private void putForCreate(K key, V value) { int hash = null == key ? 0 : hash(key); int i = indexFor(hash, table.length); /** * Look for preexisting entry for key. This will never happen for * clone or deserialize. It will only happen for construction if the * input Map is a sorted map whose ordering is inconsistent w/ equals. */ for (Entry<K,V> e = table[i]; e != null; e = e.next) { Object k; if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) { e.value = value; return; } } createEntry(hash, key, value, i); } private void putAllForCreate(Map<? extends K, ? extends V> m) { for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) putForCreate(e.getKey(), e.getValue()); } void resize(int newCapacity) { Entry[] oldTable = table; int oldCapacity = oldTable.length; if (oldCapacity == MAXIMUM_CAPACITY) { threshold = Integer.MAX_VALUE; return; } Entry[] newTable = new Entry[newCapacity]; transfer(newTable, initHashSeedAsNeeded(newCapacity)); table = newTable; threshold = (int)Math.min(newCapacity * loadFactor, MAXIMUM_CAPACITY + 1); } /** * Transfers all entries from current table to newTable. */ // 复制目前HashMap void transfer(Entry[] newTable, boolean rehash) { int newCapacity = newTable.length; for (Entry<K,V> e : table) { while(null != e) { Entry<K,V> next = e.next; //是否重新进行hash计算 if (rehash) { e.hash = null == e.key ? 0 : hash(e.key); } int i = indexFor(e.hash, newCapacity); e.next = newTable[i]; newTable[i] = e; e = next; } } } /** * Copies all of the mappings from the specified map to this map. * These mappings will replace any mappings that this map had for * any of the keys currently in the specified map. * * @param m mappings to be stored in this map * @throws NullPointerException if the specified map is null */ public void putAll(Map<? extends K, ? extends V> m) { int numKeysToBeAdded = m.size(); if (numKeysToBeAdded == 0) return; if (table == EMPTY_TABLE) { inflateTable((int) Math.max(numKeysToBeAdded * loadFactor, threshold)); } /* * Expand the map if the map if the number of mappings to be added * is greater than or equal to threshold. This is conservative; the * obvious condition is (m.size() + size) >= threshold, but this * condition could result in a map with twice the appropriate capacity, * if the keys to be added overlap with the keys already in this map. * By using the conservative calculation, we subject ourself * to at most one extra resize. */ if (numKeysToBeAdded > threshold) { int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1); if (targetCapacity > MAXIMUM_CAPACITY) targetCapacity = MAXIMUM_CAPACITY; int newCapacity = table.length; while (newCapacity < targetCapacity) newCapacity <<= 1; if (newCapacity > table.length) resize(newCapacity); } for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) put(e.getKey(), e.getValue()); } /** * Removes the mapping for the specified key from this map if present. * * @param key key whose mapping is to be removed from the map * @return the previous value associated with <tt>key</tt>, or * <tt>null</tt> if there was no mapping for <tt>key</tt>. * (A <tt>null</tt> return can also indicate that the map * previously associated <tt>null</tt> with <tt>key</tt>.) */ public V remove(Object key) { Entry<K,V> e = removeEntryForKey(key); return (e == null ? null : e.value); } /** * Removes and returns the entry associated with the specified key * in the HashMap. Returns null if the HashMap contains no mapping * for this key. */ final Entry<K,V> removeEntryForKey(Object key) { if (size == 0) { return null; } int hash = (key == null) ? 0 : hash(key); int i = indexFor(hash, table.length); Entry<K,V> prev = table[i]; Entry<K,V> e = prev; while (e != null) { Entry<K,V> next = e.next; Object k; if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) { modCount++; size--; if (prev == e) table[i] = next; else prev.next = next; e.recordRemoval(this); return e; } prev = e; e = next; } return e; } /** * Special version of remove for EntrySet using {@code Map.Entry.equals()} * for matching. */ final Entry<K,V> removeMapping(Object o) { if (size == 0 || !(o instanceof Map.Entry)) return null; Map.Entry<K,V> entry = (Map.Entry<K,V>) o; Object key = entry.getKey(); int hash = (key == null) ? 0 : hash(key); int i = indexFor(hash, table.length); Entry<K,V> prev = table[i]; Entry<K,V> e = prev; while (e != null) { Entry<K,V> next = e.next; if (e.hash == hash && e.equals(entry)) { modCount++; size--; if (prev == e) table[i] = next; else prev.next = next; e.recordRemoval(this); return e; } prev = e; e = next; } return e; } /** * Removes all of the mappings from this map. * The map will be empty after this call returns. */ public void clear() { modCount++; Arrays.fill(table, null); size = 0; } /** * Returns <tt>true</tt> if this map maps one or more keys to the * specified value. * * @param value value whose presence in this map is to be tested * @return <tt>true</tt> if this map maps one or more keys to the * specified value */ public boolean containsValue(Object value) { if (value == null) return containsNullValue(); Entry[] tab = table; for (int i = 0; i < tab.length ; i++) for (Entry e = tab[i] ; e != null ; e = e.next) if (value.equals(e.value)) return true; return false; } /** * Special-case code for containsValue with null argument */ private boolean containsNullValue() { Entry[] tab = table; for (int i = 0; i < tab.length ; i++) for (Entry e = tab[i] ; e != null ; e = e.next) if (e.value == null) return true; return false; } /** * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and * values themselves are not cloned. * * @return a shallow copy of this map */ public Object clone() { HashMap<K,V> result = null; try { result = (HashMap<K,V>)super.clone(); } catch (CloneNotSupportedException e) { // assert false; } if (result.table != EMPTY_TABLE) { result.inflateTable(Math.min( (int) Math.min( size * Math.min(1 / loadFactor, 4.0f), // we have limits... HashMap.MAXIMUM_CAPACITY), table.length)); } result.entrySet = null; result.modCount = 0; result.size = 0; result.init(); result.putAllForCreate(this); return result; } // 核心数据结构,数组+（单项）链表，LinkHashMap 是双向链表 static class Entry<K,V> implements Map.Entry<K,V> { final K key; V value; Entry<K,V> next; int hash; /** * Creates new entry. */ Entry(int h, K k, V v, Entry<K,V> n) { value = v; next = n; key = k; hash = h; } public final K getKey() { return key; } public final V getValue() { return value; } public final V setValue(V newValue) { V oldValue = value; value = newValue; return oldValue; } public final boolean equals(Object o) { if (!(o instanceof Map.Entry)) return false; Map.Entry e = (Map.Entry)o; Object k1 = getKey(); Object k2 = e.getKey(); if (k1 == k2 || (k1 != null && k1.equals(k2))) { Object v1 = getValue(); Object v2 = e.getValue(); if (v1 == v2 || (v1 != null && v1.equals(v2))) return true; } return false; } public final int hashCode() { return Objects.hashCode(getKey()) ^ Objects.hashCode(getValue()); } public final String toString() { return getKey() + "=" + getValue(); } // LinkedHashMap 有实现 void recordAccess(HashMap<K,V> m) { } // This method is invoked whenever the entry is removed from the table. void recordRemoval(HashMap<K,V> m) {} } // void addEntry(int hash, K key, V value, int bucketIndex) { if ((size >= threshold) && (null != table[bucketIndex])) { resize(2 * table.length); hash = (null != key) ? hash(key) : 0; bucketIndex = indexFor(hash, table.length); } createEntry(hash, key, value, bucketIndex); } // 它把新建的Entry节点node作为头部,链上之前的链表 void createEntry(int hash, K key, V value, int bucketIndex) { Entry<K,V> e = table[bucketIndex]; table[bucketIndex] = new Entry<K, V>(hash, key, value, e); size++; } // 类似于Entry数组的迭代器，主要是对table进行操作 private abstract class HashIterator<E> implements Iterator<E> { Entry<K,V> next; // next entry to return int expectedModCount; // For fast-fail int index; // current slot Entry<K,V> current; // current entry HashIterator() { expectedModCount = modCount; if (size > 0) { // advance to first entry Entry[] t = table; while (index < t.length && (next = t[index++]) == null) ; } } public final boolean hasNext() { return next != null; } final Entry<K,V> nextEntry() { if (modCount != expectedModCount) throw new ConcurrentModificationException(); Entry<K,V> e = next; if (e == null) throw new NoSuchElementException(); if ((next = e.next) == null) { Entry[] t = table; while (index < t.length && (next = t[index++]) == null) ; } current = e; return e; } public void remove() { if (current == null) throw new IllegalStateException(); if (modCount != expectedModCount) throw new ConcurrentModificationException(); Object k = current.key; current = null; HashMap.this.removeEntryForKey(k); expectedModCount = modCount; } } //------------------- private final class ValueIterator extends HashIterator<V> { public V next() { return nextEntry().value; } } private final class KeyIterator extends HashIterator<K> { public K next() { return nextEntry().getKey(); } } private final class EntryIterator extends HashIterator<Map.Entry<K,V>> { public Map.Entry<K,V> next() { return nextEntry(); } } // Subclass overrides these to alter behavior of views' iterator() method Iterator<K> newKeyIterator() { return new KeyIterator(); } Iterator<V> newValueIterator() { return new ValueIterator(); } Iterator<Map.Entry<K,V>> newEntryIterator() { return new EntryIterator(); } private transient Set<Map.Entry<K,V>> entrySet = null; // public Set<K> keySet() { // Set<K> ks = keySet; // return (ks != null ? ks : (keySet = new KeySet())); // } private final class KeySet extends AbstractSet<K> { public Iterator<K> iterator() { return newKeyIterator(); } public int size() { return size; } public boolean contains(Object o) { return containsKey(o); } public boolean remove(Object o) { return HashMap.this.removeEntryForKey(o) != null; } public void clear() { HashMap.this.clear(); } } public Collection<V> values() { Collection<V> vs = values; return (vs != null ? vs : (values = new Values())); } private final class Values extends AbstractCollection<V> { public Iterator<V> iterator() { return newValueIterator(); } public int size() { return size; } public boolean contains(Object o) { return containsValue(o); } public void clear() { HashMap.this.clear(); } } public Set<Map.Entry<K,V>> entrySet() { return entrySet0(); } private Set<Map.Entry<K,V>> entrySet0() { Set<Map.Entry<K,V>> es = entrySet; return es != null ? es : (entrySet = new EntrySet()); } private final class EntrySet extends AbstractSet<Map.Entry<K,V>> { public Iterator<Map.Entry<K,V>> iterator() { return newEntryIterator(); } public boolean contains(Object o) { if (!(o instanceof Map.Entry)) return false; Map.Entry<K,V> e = (Map.Entry<K,V>) o; Entry<K,V> candidate = getEntry(e.getKey()); return candidate != null && candidate.equals(e); } public boolean remove(Object o) { return removeMapping(o) != null; } public int size() { return size; } public void clear() { HashMap.this.clear(); } } private void writeObject(java.io.ObjectOutputStream s) throws IOException { // Write out the threshold, loadfactor, and any hidden stuff s.defaultWriteObject(); // Write out number of buckets if (table==EMPTY_TABLE) { s.writeInt(roundUpToPowerOf2(threshold)); } else { s.writeInt(table.length); } // Write out size (number of Mappings) s.writeInt(size); // Write out keys and values (alternating) if (size > 0) { for(Map.Entry<K,V> e : entrySet0()) { s.writeObject(e.getKey()); s.writeObject(e.getValue()); } } } private static final long serialVersionUID = 362498820763181265L; private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException { // Read in the threshold (ignored), loadfactor, and any hidden stuff s.defaultReadObject(); if (loadFactor <= 0 || Float.isNaN(loadFactor)) { throw new InvalidObjectException("Illegal load factor: " + loadFactor); } // set other fields that need values table = (Entry<K,V>[]) EMPTY_TABLE; // Read in number of buckets s.readInt(); // ignored. // Read number of mappings int mappings = s.readInt(); if (mappings < 0) throw new InvalidObjectException("Illegal mappings count: " + mappings); // capacity chosen by number of mappings and desired load (if >= 0.25) int capacity = (int) Math.min( mappings * Math.min(1 / loadFactor, 4.0f), // we have limits... HashMap.MAXIMUM_CAPACITY); // allocate the bucket array; if (mappings > 0) { inflateTable(capacity); } else { threshold = capacity; } init(); // Give subclass a chance to do its thing. // Read the keys and values, and put the mappings in the HashMap for (int i = 0; i < mappings; i++) { K key = (K) s.readObject(); V value = (V) s.readObject(); putForCreate(key, value); } } // These methods are used when serializing HashSets int capacity() { return table.length; } float loadFactor() { return loadFactor; } }
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