hashMap 属性说明

public class HashMap<K,V>
    extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable
{

    /**
     * The default initial capacity - MUST be a power of two.
     */
    static final int DEFAULT_INITIAL_CAPACITY = 16;//默认初始容量（数组大小）

    /**
     * The maximum capacity, used if a higher value is implicitly specified
     * by either of the constructors with arguments.
     * MUST be a power of two <= 1<<30.
     */
    static final int MAXIMUM_CAPACITY = 1 << 30;//1073741824最大的容量范围

    /**
     * The load factor used when none specified in constructor.
     */
    static final float DEFAULT_LOAD_FACTOR = 0.75f;//加载因子默认0.75

    /**
     * The table, resized as necessary. Length MUST Always be a power of two.
     */
    transient Entry[] table;//存储数据的entry数组

    /**
     * The number of key-value mappings contained in this map.
     */
    transient int size;//数组的大小

    /**
     * The next size value at which to resize (capacity * load factor).
     * @serial
     */
    int threshold;//临界值=加载因子*初始容量（当size大于临界值就会出现数组扩充到原来2 倍）

    /**
     * The load factor for the hash table.
     *
     * @serial
     */
    final float loadFactor;//加载因子默认0.75

    /**
     * The number of times this HashMap has been structurally modified
     * Structural modifications are those that change the number of mappings in
     * the HashMap or otherwise modify its internal structure (e.g.,
     * rehash).  This field is used to make iterators on Collection-views of
     * the HashMap fail-fast.  (See ConcurrentModificationException).
     */
    transient volatile int modCount;//修改的次数