[Java] Java源码解析HashMap成员变量

/**
 * the default initial capacity - must be a power of two.
 **/
static final int default_initial_capacity = 1 << 4; // aka 16

/**
 * 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;

/**
 * the load factor used when none specified in constructor.
 **/
static final float default_load_factor = 0.75f;

/**
 * the bin count threshold for using a tree rather than list for a
 * bin. bins are converted to trees when adding an element to a
 * bin with at least this many nodes. the value must be greater
 * than 2 and should be at least 8 to mesh with assumptions in
 * tree removal about conversion back to plain bins upon
 * shrinkage.
 **/
static final int treeify_threshold = 8;
/**
 * the bin count threshold for untreeifying a (split) bin during a
 * resize operation. should be less than treeify_threshold, and at
 * most 6 to mesh with shrinkage detection under removal.
 **/
static final int untreeify_threshold = 6;
/**
 * the smallest table capacity for which bins may be treeified.
 * (otherwise the table is resized if too many nodes in a bin.)
 * should be at least 4 * treeify_threshold to avoid conflicts
 * between resizing and treeification thresholds.
 **/
static final int min_treeify_capacity = 64;

/**
 * the table, initialized on first use, and resized as
 * necessary. when allocated, length is always a power of two.
 * (we also tolerate length zero in some operations to allow
 * bootstrapping mechanics that are currently not needed.)
 **/
transient node<k,v>[] table;

/**
 * holds cached entryset(). note that abstractmap fields are used
 * for keyset() and values().
 **/
transient set<map.entry<k,v>> entryset;

/**
 * the number of key-value mappings contained in this map.
 **/
transient int size;
/**
 * 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 int modcount;
/**
 * the next size value at which to resize (capacity * load factor).
 * @serial
 **/
// (the javadoc description is true upon serialization.
// additionally, if the table array has not been allocated, this
// field holds the initial array capacity, or zero signifying
// default_initial_capacity.)
int threshold;
/**
 * the load factor for the hash table.
 *
 * @serial
 **/
final float loadfactor;