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/*
* Copyright (c) 1997, 2025, 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package
java
.
util
;
import
java
.
io
.
IOException
;
import
java
.
io
.
InvalidObjectException
;
import
java
.
io
.
ObjectInputStream
;
import
java
.
io
.
Serializable
;
import
java
.
lang
.
reflect
.
ParameterizedType
;
import
java
.
lang
.
reflect
.
Type
;
import
java
.
util
.
function
.
BiConsumer
;
import
java
.
util
.
function
.
BiFunction
;
import
java
.
util
.
function
.
Consumer
;
import
java
.
util
.
function
.
Function
;
import
jdk
.
internal
.
access
.
SharedSecrets
;
/**
* Hash table based implementation of the {@code Map} interface. This
* implementation provides all of the optional map operations, and permits
* {@code null} values and the {@code null} key. (The {@code HashMap}
* class is roughly equivalent to {@code Hashtable}, except that it is
* unsynchronized and permits nulls.) This class makes no guarantees as to
* the order of the map; in particular, it does not guarantee that the order
* will remain constant over time.
*
* <p>This implementation provides constant-time performance for the basic
* operations ({@code get} and {@code put}), assuming the hash function
* disperses the elements properly among the buckets. Iteration over
* collection views requires time proportional to the "capacity" of the
* {@code HashMap} instance (the number of buckets) plus its size (the number
* of key-value mappings). Thus, it's very important not to set the initial
* capacity too high (or the load factor too low) if iteration performance is
* important.
*
* <p>An instance of {@code HashMap} has two parameters that affect its
* performance: <i>initial capacity</i> and <i>load factor</i>. The
* <i>capacity</i> is the number of buckets in the hash table, and the initial
* capacity is simply the capacity at the time the hash table is created. The
* <i>load factor</i> is a measure of how full the hash table is allowed to
* get before its capacity is automatically increased. When the number of
* entries in the hash table exceeds the product of the load factor and the
* current capacity, the hash table is <i>rehashed</i> (that is, internal data
* structures are rebuilt) so that the hash table has approximately twice the
* number of buckets.
*
* <p>As a general rule, the default load factor (.75) offers a good
* tradeoff between time and space costs. Higher values decrease the
* space overhead but increase the lookup cost (reflected in most of
* the operations of the {@code HashMap} class, including
* {@code get} and {@code put}). The expected number of entries in
* the map and its load factor should be taken into account when
* setting its initial capacity, so as to minimize the number of
* rehash operations. If the initial capacity is greater than the
* maximum number of entries divided by the load factor, no rehash
* operations will ever occur.
*
* <p>If many mappings are to be stored in a {@code HashMap}
* instance, creating it with a sufficiently large capacity will allow
* the mappings to be stored more efficiently than letting it perform
* automatic rehashing as needed to grow the table. Note that using
* many keys with the same {@code hashCode()} is a sure way to slow
* down performance of any hash table. To ameliorate impact, when keys
* are {@link Comparable}, this class may use comparison order among
* keys to help break ties.
*
* <p><strong>Note that this implementation is not synchronized.</strong>
* If multiple threads access a hash map concurrently, and at least one of
* the threads modifies the map structurally, it <i>must</i> be
* synchronized externally. (A structural modification is any operation
* that adds or deletes one or more mappings; merely changing the value
* associated with a key that an instance already contains is not a
* structural modification.) This is typically accomplished by
* synchronizing on some object that naturally encapsulates the map.
*
* If no such object exists, the map should be "wrapped" using the
* {@link Collections#synchronizedMap Collections.synchronizedMap}
* method. This is best done at creation time, to prevent accidental
* unsynchronized access to the map:<pre>
* Map m = Collections.synchronizedMap(new HashMap(...));</pre>
*
* <p>The iterators returned by all of this class's "collection view methods"
* are <i>fail-fast</i>: if the map is structurally modified at any time after
* the iterator is created, in any way except through the iterator's own
* {@code remove} method, the iterator will throw a
* {@link ConcurrentModificationException}. Thus, in the face of concurrent
* modification, the iterator fails quickly and cleanly, rather than risking
* arbitrary, non-deterministic behavior at an undetermined time in the
* future.
*
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
* throw {@code ConcurrentModificationException} on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: <i>the fail-fast behavior of iterators
* should be used only to detect bugs.</i>
*
* <p>This class is a member of the
* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
* Java Collections Framework</a>.
*
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*
* @author Doug Lea
* @author Josh Bloch
* @author Arthur van Hoff
* @author Neal Gafter
* @see Object#hashCode()
* @see Collection
* @see Map
* @see TreeMap
* @see Hashtable
* @since 1.2
*/
public
class
HashMap
<
K
,
V
>
extends
AbstractMap
<
K
,
V
>
implements
Map
<
K
,
V
>,
Cloneable
,
Serializable
{
@
java
.
io
.
Serial
private
static
final
long
serialVersionUID
=
362498820763181265L
;
/*
* Implementation notes.
*
* This map usually acts as a binned (bucketed) hash table, but
* when bins get too large, they are transformed into bins of
* TreeNodes, each structured similarly to those in
* java.util.TreeMap. Most methods try to use normal bins, but
* relay to TreeNode methods when applicable (simply by checking
* instanceof a node). Bins of TreeNodes may be traversed and
* used like any others, but additionally support faster lookup
* when overpopulated. However, since the vast majority of bins in
* normal use are not overpopulated, checking for existence of
* tree bins may be delayed in the course of table methods.
*
* Tree bins (i.e., bins whose elements are all TreeNodes) are
* ordered primarily by hashCode, but in the case of ties, if two
* elements are of the same "class C implements Comparable<C>",
* type then their compareTo method is used for ordering. (We
* conservatively check generic types via reflection to validate
* this -- see method comparableClassFor). The added complexity
* of tree bins is worthwhile in providing worst-case O(log n)
* operations when keys either have distinct hashes or are
* orderable, Thus, performance degrades gracefully under
* accidental or malicious usages in which hashCode() methods
* return values that are poorly distributed, as well as those in
* which many keys share a hashCode, so long as they are also
* Comparable. (If neither of these apply, we may waste about a
* factor of two in time and space compared to taking no
* precautions. But the only known cases stem from poor user
* programming practices that are already so slow that this makes
* little difference.)
*
* Because TreeNodes are about twice the size of regular nodes, we
* use them only when bins contain enough nodes to warrant use
* (see TREEIFY_THRESHOLD). And when they become too small (due to
* removal or resizing) they are converted back to plain bins. In
* usages with well-distributed user hashCodes, tree bins are
* rarely used. Ideally, under random hashCodes, the frequency of
* nodes in bins follows a Poisson distribution
* (http://en.wikipedia.org/wiki/Poisson_distribution) with a
* parameter of about 0.5 on average for the default resizing
* threshold of 0.75, although with a large variance because of
* resizing granularity. Ignoring variance, the expected
* occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
* factorial(k)). The first values are:
*
* 0: 0.60653066
* 1: 0.30326533
* 2: 0.07581633
* 3: 0.01263606
* 4: 0.00157952
* 5: 0.00015795
* 6: 0.00001316
* 7: 0.00000094
* 8: 0.00000006
* more: less than 1 in ten million
*
* The root of a tree bin is normally its first node. However,
* sometimes (currently only upon Iterator.remove), the root might
* be elsewhere, but can be recovered following parent links
* (method TreeNode.root()).
*
* All applicable internal methods accept a hash code as an
* argument (as normally supplied from a public method), allowing
* them to call each other without recomputing user hashCodes.
* Most internal methods also accept a "tab" argument, that is
* normally the current table, but may be a new or old one when
* resizing or converting.
*
* When bin lists are treeified, split, or untreeified, we keep
* them in the same relative access/traversal order (i.e., field
* Node.next) to better preserve locality, and to slightly
* simplify handling of splits and traversals that invoke
* iterator.remove. When using comparators on insertion, to keep a
* total ordering (or as close as is required here) across
* rebalancings, we compare classes and identityHashCodes as
* tie-breakers.
*
* The use and transitions among plain vs tree modes is
* complicated by the existence of subclass LinkedHashMap. See
* below for hook methods defined to be invoked upon insertion,
* removal and access that allow LinkedHashMap internals to
* otherwise remain independent of these mechanics. (This also
* requires that a map instance be passed to some utility methods
* that may create new nodes.)
*
* The concurrent-programming-like SSA-based coding style helps
* avoid aliasing errors amid all of the twisty pointer operations.
*/
/**
* 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
;
/**
* Basic hash bin node, used for most entries. (See below for
* TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
*/
static
class
Node
<
K
,
V
>
implements
Map
.
Entry
<
K
,
V
> {
final
int
hash
;
final
K
key
;
V
value
;
Node
<
K
,
V
>
next
;
Node
(
int
hash
,
K
key
,
V
value
,
Node
<
K
,
V
>
next
) {
this
.
hash
=
hash
;
this
.
key
=
key
;
this
.
value
=
value
;
this
.
next
=
next
;
}
public
final
K
getKey
() {
return
key
; }
public
final
V
getValue
() {
return
value
; }
public
final
String
toString
() {
return
key
+
"="
+
value
; }
public
final
int
hashCode
() {
return
Objects
.
hashCode
(
key
) ^
Objects
.
hashCode
(
value
);
}
public
final
V
setValue
(
V
newValue
) {
V
oldValue
=
value
;
value
=
newValue
;
return
oldValue
;
}
public
final
boolean
equals
(
Object
o
) {
if
(
o
==
this
)
return
true
;
return
o
instanceof
Map
.
Entry
<?, ?>
e
&&
Objects
.
equals
(
key
,
e
.
getKey
())
&&
Objects
.
equals
(
value
,
e
.
getValue
());
}
}
/* ---------------- Static utilities -------------- */
/**
* Computes key.hashCode() and spreads (XORs) higher bits of hash
* to lower. Because the table uses power-of-two masking, sets of
* hashes that vary only in bits above the current mask will
* always collide. (Among known examples are sets of Float keys
* holding consecutive whole numbers in small tables.) So we
* apply a transform that spreads the impact of higher bits
* downward. There is a tradeoff between speed, utility, and
* quality of bit-spreading. Because many common sets of hashes
* are already reasonably distributed (so don't benefit from
* spreading), and because we use trees to handle large sets of
* collisions in bins, we just XOR some shifted bits in the
* cheapest possible way to reduce systematic lossage, as well as
* to incorporate impact of the highest bits that would otherwise
* never be used in index calculations because of table bounds.
*/
static
final
int
hash
(
Object
key
) {
int
h
;
return
(
key
==
null
) ?
0
: (
h
=
key
.
hashCode
()) ^ (
h
>>>
16
);
}
/**
* Returns x's Class if it is of the form "class C implements
* Comparable<C>", else null.
*/
static
Class
<?>
comparableClassFor
(
Object
x
) {
if
(
x
instanceof
Comparable
) {
Class
<?>
c
;
Type
[]
ts
,
as
;
ParameterizedType
p
;
if
((
c
=
x
.
getClass
()) ==
String
.
class
)
// bypass checks
return
c
;
if
((
ts
=
c
.
getGenericInterfaces
()) !=
null
) {
for
(
Type
t
:
ts
) {
if
((
t
instanceof
ParameterizedType
) &&
((
p
= (
ParameterizedType
)
t
).
getRawType
() ==
Comparable
.
class
) &&
(
as
=
p
.
getActualTypeArguments
()) !=
null
&&
as
.
length
==
1
&&
as
[
0
] ==
c
)
// type arg is c
return
c
;
}
}
}
return
null
;
}
/**
* Returns k.compareTo(x) if x matches kc (k's screened comparable
* class), else 0.
*/
@
SuppressWarnings
(
"unchecked"
)
// for cast to Comparable
static
int
compareComparables
(
Class
<?>
kc
,
Object
k
,
Object
x
) {
return
(
x
==
null
||
x
.
getClass
() !=
kc
?
0
:
((
Comparable
)
k
).
compareTo
(
x
));
}
/**
* Returns a power of two size for the given target capacity.
*/
static
final
int
tableSizeFor
(
int
cap
) {
int
n
= -
1
>>>
Integer
.
numberOfLeadingZeros
(
cap
-
1
);
return
(
n
<
0
) ?
1
: (
n
>=
MAXIMUM_CAPACITY
) ?
MAXIMUM_CAPACITY
:
n
+
1
;
}
/* ---------------- Fields -------------- */
/**
* 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
;
/* ---------------- Public operations -------------- */
/**
* 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
* or the load factor is nonpositive
*/
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
;
this
.
threshold
=
tableSizeFor
(
initialCapacity
);
}
/**
* 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.
*/
public
HashMap
(
int
initialCapacity
) {
this
(
initialCapacity
,
DEFAULT_LOAD_FACTOR
);
}
/**
* Constructs an empty {@code HashMap} with the default initial capacity
* (16) and the default load factor (0.75).
*/
public
HashMap
() {
this
.
loadFactor
=
DEFAULT_LOAD_FACTOR
;
// all other fields defaulted
}
/**
* Constructs a new {@code HashMap} with the same mappings as the
* specified {@code Map}. The {@code HashMap} is created with
* default load factor (0.75) and an initial capacity sufficient to
* hold the mappings in the specified {@code Map}.
*
* @param m the map whose mappings are to be placed in this map
* @throws NullPointerException if the specified map is null
*/
@
SuppressWarnings
(
"this-escape"
)
public
HashMap
(
Map
<?
extends
K
, ?
extends
V
>
m
) {
this
.
loadFactor
=
DEFAULT_LOAD_FACTOR
;
putMapEntries
(
m
,
false
);
}
// Fast path for HashMap-to-HashMap copying. Eliminates megamorphic
// call sites described in JDK-8368292 by walking the source table.
// Also reuses pre-computed hash codes, avoiding redundant
// hashCode() calls.
private
void
putHashMapEntries
(
HashMap
<?
extends
K
, ?
extends
V
>
src
,
boolean
evict
) {
Node
<?
extends
K
, ?
extends
V
>[]
tab
;
if
(
src
.
size
>
0
&& (
tab
=
src
.
table
) !=
null
) {
for
(
Node
<?
extends
K
, ?
extends
V
>
e
:
tab
) {
for
(;
e
!=
null
;
e
=
e
.
next
) {
putVal
(
e
.
hash
,
e
.
key
,
e
.
value
,
false
,
evict
);
}
}
}
}
/**
* Implements Map.putAll and Map constructor.
*
* @param m the map
* @param evict false when initially constructing this map, else
* true (relayed to method afterNodeInsertion).
*/
final
void
putMapEntries
(
Map
<?
extends
K
, ?
extends
V
>
m
,
boolean
evict
) {
int
s
=
m
.
size
();
if
(
s
>
0
) {
if
(
table
==
null
) {
// pre-size
double
dt
=
Math
.
ceil
(
s
/ (
double
)
loadFactor
);
int
t
= ((
dt
< (
double
)
MAXIMUM_CAPACITY
) ?
(
int
)
dt
:
MAXIMUM_CAPACITY
);
if
(
t
>
threshold
)
threshold
=
tableSizeFor
(
t
);
}
else
{
// Because of linked-list bucket constraints, we cannot
// expand all at once, but can reduce total resize
// effort by repeated doubling now vs later
while
(
s
>
threshold
&&
table
.
length
<
MAXIMUM_CAPACITY
)
resize
();
}
// Fast path when source is a HashMap, or an UnmodifiableMap
// wrapping a HashMap. See JDK-8368292.
Map
<?
extends
K
, ?
extends
V
>
hm
;
if
((
hm
=
m
).
getClass
() ==
HashMap
.
class
||
m
instanceof
Collections
.
UnmodifiableMap
<?
extends
K
, ?
extends
V
>
umap
&& (
hm
=
umap
.
m
).
getClass
() ==
HashMap
.
class
) {
putHashMapEntries
((
HashMap
<?
extends
K
, ?
extends
V
>)
hm
,
evict
);
return
;
}
for
(
Map
.
Entry
<?
extends
K
, ?
extends
V
>
e
:
m
.
entrySet
()) {
K
key
=
e
.
getKey
();
V
value
=
e
.
getValue
();
putVal
(
hash
(
key
),
key
,
value
,
false
,
evict
);
}
}
}
/**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map
*/
public
int
size
() {
return
size
;
}
/**
* Returns {@code true} if this map contains no key-value mappings.
*
* @return {@code true} if this map contains no key-value mappings
*/
public
boolean
isEmpty
() {
return
size
==
0
;
}
/**
* Returns the value to which the specified key is mapped,
* or {@code null} if this map contains no mapping for the key.
*
* <p>More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key==null ? k==null :
* key.equals(k))}, then this method returns {@code v}; otherwise
* it returns {@code null}. (There can be at most one such mapping.)
*
* <p>A return value of {@code null} does not <i>necessarily</i>
* indicate that the map contains no mapping for the key; it's also
* possible that the map explicitly maps the key to {@code null}.
* The {@link #containsKey containsKey} operation may be used to
* distinguish these two cases.
*
* @see #put(Object, Object)
*/
public
V
get
(
Object
key
) {
Node
<
K
,
V
>
e
;
return
(
e
=
getNode
(
key
)) ==
null
?
null
:
e
.
value
;
}
/**
* Implements Map.get and related methods.
*
* @param key the key
* @return the node, or null if none
*/
final
Node
<
K
,
V
>
getNode
(
Object
key
) {
Node
<
K
,
V
>[]
tab
;
Node
<
K
,
V
>
first
,
e
;
int
n
,
hash
;
K
k
;
if
((
tab
=
table
) !=
null
&& (
n
=
tab
.
length
) >
0
&&
(
first
=
tab
[(
n
-
1
) & (
hash
=
hash
(
key
))]) !=
null
) {
if
(
first
.
hash
==
hash
&&
// always check first node
((
k
=
first
.
key
) ==
key
|| (
key
!=
null
&&
key
.
equals
(
k
))))
return
first
;
if
((
e
=
first
.
next
) !=
null
) {
if
(
first
instanceof
TreeNode
)
return
((
TreeNode
<
K
,
V
>)
first
).
getTreeNode
(
hash
,
key
);
do
{
if
(
e
.
hash
==
hash
&&
((
k
=
e
.
key
) ==
key
|| (
key
!=
null
&&
key
.
equals
(
k
))))
return
e
;
}
while
((
e
=
e
.
next
) !=
null
);
}
}
return
null
;
}
/**
* Returns {@code true} if this map contains a mapping for the
* specified key.
*
* @param key The key whose presence in this map is to be tested
* @return {@code true} if this map contains a mapping for the specified
* key.
*/
public
boolean
containsKey
(
Object
key
) {
return
getNode
(
key
) !=
null
;
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for the key, the old
* value is replaced.
*
* @param key key with which the specified value is to be associated
* @param value value to be associated with the specified key
* @return the previous value associated with {@code key}, or
* {@code null} if there was no mapping for {@code key}.
* (A {@code null} return can also indicate that the map
* previously associated {@code null} with {@code key}.)
*/
public
V
put
(
K
key
,
V
value
) {
return
putVal
(
hash
(
key
),
key
,
value
,
false
,
true
);
}
/**
* Implements Map.put and related methods.
*
* @param hash hash for key
* @param key the key
* @param value the value to put
* @param onlyIfAbsent if true, don't change existing value
* @param evict if false, the table is in creation mode.
* @return previous value, or null if none
*/
final
V
putVal
(
int
hash
,
K
key
,
V
value
,
boolean
onlyIfAbsent
,
boolean
evict
) {
Node
<
K
,
V
>[]
tab
;
Node
<
K
,
V
>
p
;
int
n
,
i
;
if
((
tab
=
table
) ==
null
|| (
n
=
tab
.
length
) ==
0
)
n
= (
tab
=
resize
()).
length
;
if
((
p
=
tab
[
i
= (
n
-
1
) &
hash
]) ==
null
)
tab
[
i
] =
newNode
(
hash
,
key
,
value
,
null
);
else
{
Node
<
K
,
V
>
e
;
K
k
;
if
(
p
.
hash
==
hash
&&
((
k
=
p
.
key
) ==
key
|| (
key
!=
null
&&
key
.
equals
(
k
))))
e
=
p
;
else
if
(
p
instanceof
TreeNode
)
e
= ((
TreeNode
<
K
,
V
>)
p
).
putTreeVal
(
this
,
tab
,
hash
,
key
,
value
);
else
{
for
(
int
binCount
=
0
; ; ++
binCount
) {
if
((
e
=
p
.
next
) ==
null
) {
p
.
next
=
newNode
(
hash
,
key
,
value
,
null
);
if
(
binCount
>=
TREEIFY_THRESHOLD
-
1
)
// -1 for 1st
treeifyBin
(
tab
,
hash
);
break
;
}
if
(
e
.
hash
==
hash
&&
((
k
=
e
.
key
) ==
key
|| (
key
!=
null
&&
key
.
equals
(
k
))))
break
;
p
=
e
;
}
}
if
(
e
!=
null
) {
// existing mapping for key
V
oldValue
=
e
.
value
;
if
(!
onlyIfAbsent
||
oldValue
==
null
)
e
.
value
=
value
;
afterNodeAccess
(
e
);
return
oldValue
;
}
}
++
modCount
;
if
(++
size
>
threshold
)
resize
();
afterNodeInsertion
(
evict
);
return
null
;
}
/**
* Initializes or doubles table size. If null, allocates in
* accord with initial capacity target held in field threshold.
* Otherwise, because we are using power-of-two expansion, the
* elements from each bin must either stay at same index, or move
* with a power of two offset in the new table.
*
* @return the table
*/
final
Node
<
K
,
V
>[]
resize
() {
Node
<
K
,
V
>[]
oldTab
=
table
;
int
oldCap
= (
oldTab
==
null
) ?
0
:
oldTab
.
length
;
int
oldThr
=
threshold
;
int
newCap
,
newThr
=
0
;
if
(
oldCap
>
0
) {
if
(
oldCap
>=
MAXIMUM_CAPACITY
) {
threshold
=
Integer
.
MAX_VALUE
;
return
oldTab
;
}
else
if
((
newCap
=
oldCap
<<
1
) <
MAXIMUM_CAPACITY
&&
oldCap
>=
DEFAULT_INITIAL_CAPACITY
)
newThr
=
oldThr
<<
1
;
// double threshold
}
else
if
(
oldThr
>
0
)
// initial capacity was placed in threshold
newCap
=
oldThr
;
else
{
// zero initial threshold signifies using defaults
newCap
=
DEFAULT_INITIAL_CAPACITY
;
newThr
= (
int
)(
DEFAULT_LOAD_FACTOR
*
DEFAULT_INITIAL_CAPACITY
);
}
if
(
newThr
==
0
) {
float
ft
= (
float
)
newCap
*
loadFactor
;
newThr
= (
newCap
<
MAXIMUM_CAPACITY
&&
ft
< (
float
)
MAXIMUM_CAPACITY
?
(
int
)
ft
:
Integer
.
MAX_VALUE
);
}
threshold
=
newThr
;
@
SuppressWarnings
({
"rawtypes"
,
"unchecked"
})
Node
<
K
,
V
>[]
newTab
= (
Node
<
K
,
V
>[])
new
Node
[
newCap
];
table
=
newTab
;
if
(
oldTab
!=
null
) {
for
(
int
j
=
0
;
j
<
oldCap
; ++
j
) {
Node
<
K
,
V
>
e
;
if
((
e
=
oldTab
[
j
]) !=
null
) {
oldTab
[
j
] =
null
;
if
(
e
.
next
==
null
)
newTab
[
e
.
hash
& (
newCap
-
1
)] =
e
;
else
if
(
e
instanceof
TreeNode
)
((
TreeNode
<
K
,
V
>)
e
).
split
(
this
,
newTab
,
j
,
oldCap
);
else
{
// preserve order
Node
<
K
,
V
>
loHead
=
null
,
loTail
=
null
;
Node
<
K
,
V
>
hiHead
=
null
,
hiTail
=
null
;
Node
<
K
,
V
>
next
;
do
{
next
=
e
.
next
;
if
((
e
.
hash
&
oldCap
) ==
0
) {
if
(
loTail
==
null
)
loHead
=
e
;
else
loTail
.
next
=
e
;
loTail
=
e
;
}
else
{
if
(
hiTail
==
null
)
hiHead
=
e
;
else
hiTail
.
next
=
e
;
hiTail
=
e
;
}
}
while
((
e
=
next
) !=
null
);
if
(
loTail
!=
null
) {
loTail
.
next
=
null
;
newTab
[
j
] =
loHead
;
}
if
(
hiTail
!=
null
) {
hiTail
.
next
=
null
;
newTab
[
j
+
oldCap
] =
hiHead
;
}
}
}
}
}
return
newTab
;
}
/**
* Replaces all linked nodes in bin at index for given hash unless
* table is too small, in which case resizes instead.
*/
final
void
treeifyBin
(
Node
<
K
,
V
>[]
tab
,
int
hash
) {
int
n
,
index
;
Node
<
K
,
V
>
e
;
if
(
tab
==
null
|| (
n
=
tab
.
length
) <
MIN_TREEIFY_CAPACITY
)
resize
();
else
if
((
e
=
tab
[
index
= (
n
-
1
) &
hash
]) !=
null
) {
TreeNode
<
K
,
V
>
hd
=
null
,
tl
=
null
;
do
{
TreeNode
<
K
,
V
>
p
=
replacementTreeNode
(
e
,
null
);
if
(
tl
==
null
)
hd
=
p
;
else
{
p
.
prev
=
tl
;
tl
.
next
=
p
;
}
tl
=
p
;
}
while
((
e
=
e
.
next
) !=
null
);
if
((
tab
[
index
] =
hd
) !=
null
)
hd
.
treeify
(
tab
);
}
}
/**
* 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
) {
putMapEntries
(
m
,
true
);
}
/**
* 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 {@code key}, or
* {@code null} if there was no mapping for {@code key}.
* (A {@code null} return can also indicate that the map
* previously associated {@code null} with {@code key}.)
*/
public
V
remove
(
Object
key
) {
Node
<
K
,
V
>
e
;
return
(
e
=
removeNode
(
hash
(
key
),
key
,
null
,
false
,
true
)) ==
null
?
null
:
e
.
value
;
}
/**
* Implements Map.remove and related methods.
*
* @param hash hash for key
* @param key the key
* @param value the value to match if matchValue, else ignored
* @param matchValue if true only remove if value is equal
* @param movable if false do not move other nodes while removing
* @return the node, or null if none
*/
final
Node
<
K
,
V
>
removeNode
(
int
hash
,
Object
key
,
Object
value
,
boolean
matchValue
,
boolean
movable
) {
Node
<
K
,
V
>[]
tab
;
Node
<
K
,
V
>
p
;
int
n
,
index
;
if
((
tab
=
table
) !=
null
&& (
n
=
tab
.
length
) >
0
&&
(
p
=
tab
[
index
= (
n
-
1
) &
hash
]) !=
null
) {
Node
<
K
,
V
>
node
=
null
,
e
;
K
k
;
V
v
;
if
(
p
.
hash
==
hash
&&
((
k
=
p
.
key
) ==
key
|| (
key
!=
null
&&
key
.
equals
(
k
))))
node
=
p
;
else
if
((
e
=
p
.
next
) !=
null
) {
if
(
p
instanceof
TreeNode
)
node
= ((
TreeNode
<
K
,
V
>)
p
).
getTreeNode
(
hash
,
key
);
else
{
do
{
if
(
e
.
hash
==
hash
&&
((
k
=
e
.
key
) ==
key
||
(
key
!=
null
&&
key
.
equals
(
k
)))) {
node
=
e
;
break
;
}
p
=
e
;
}
while
((
e
=
e
.
next
) !=
null
);
}
}
if
(
node
!=
null
&& (!
matchValue
|| (
v
=
node
.
value
) ==
value
||
(
value
!=
null
&&
value
.
equals
(
v
)))) {
if
(
node
instanceof
TreeNode
)
((
TreeNode
<
K
,
V
>)
node
).
removeTreeNode
(
this
,
tab
,
movable
);
else
if
(
node
==
p
)
tab
[
index
] =
node
.
next
;
else
p
.
next
=
node
.
next
;
++
modCount
;
--
size
;
afterNodeRemoval
(
node
);
return
node
;
}
}
return
null
;
}
/**
* Removes all of the mappings from this map.
* The map will be empty after this call returns.
*/
public
void
clear
() {
Node
<
K
,
V
>[]
tab
;
modCount
++;
if
((
tab
=
table
) !=
null
&&
size
>
0
) {
size
=
0
;
for
(
int
i
=
0
;
i
<
tab
.
length
; ++
i
)
tab
[
i
] =
null
;
}
}
/**
* Returns {@code true} 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 {@code true} if this map maps one or more keys to the
* specified value
*/
public
boolean
containsValue
(
Object
value
) {
Node
<
K
,
V
>[]
tab
;
V
v
;
if
((
tab
=
table
) !=
null
&&
size
>
0
) {
for
(
Node
<
K
,
V
>
e
:
tab
) {
for
(;
e
!=
null
;
e
=
e
.
next
) {
if
((
v
=
e
.
value
) ==
value
||
(
value
!=
null
&&
value
.
equals
(
v
)))
return
true
;
}
}
}
return
false
;
}
/**
* Returns a {@link Set} view of the keys contained in this map.
* The set is backed by the map, so changes to the map are
* reflected in the set, and vice-versa. If the map is modified
* while an iteration over the set is in progress (except through
* the iterator's own {@code remove} operation), the results of
* the iteration are undefined. The set supports element removal,
* which removes the corresponding mapping from the map, via the
* {@code Iterator.remove}, {@code Set.remove},
* {@code removeAll}, {@code retainAll}, and {@code clear}
* operations. It does not support the {@code add} or {@code addAll}
* operations.
*
* @return a set view of the keys contained in this map
*/
public
Set
<
K
>
keySet
() {
Set
<
K
>
ks
=
keySet
;
if
(
ks
==
null
) {
ks
=
new
KeySet
();
keySet
=
ks
;
}
return
ks
;
}
/**
* Prepares the array for {@link Collection#toArray(Object[])} implementation.
* If supplied array is smaller than this map size, a new array is allocated.
* If supplied array is bigger than this map size, a null is written at size index.
*
* @param a an original array passed to {@code toArray()} method
* @param <T> type of array elements
* @return an array ready to be filled and returned from {@code toArray()} method.
*/
@
SuppressWarnings
(
"unchecked"
)
final
<
T
>
T
[]
prepareArray
(
T
[]
a
) {
int
size
=
this
.
size
;
if
(
a
.
length
<
size
) {
return
(
T
[])
java
.
lang
.
reflect
.
Array
.
newInstance
(
a
.
getClass
().
getComponentType
(),
size
);
}
if
(
a
.
length
>
size
) {
a
[
size
] =
null
;
}
return
a
;
}
/**
* Fills an array with this map keys and returns it. This method assumes
* that input array is big enough to fit all the keys. Use
* {@link #prepareArray(Object[])} to ensure this.
*
* @param a an array to fill
* @param <T> type of array elements
* @return supplied array
*/
<
T
>
T
[]
keysToArray
(
T
[]
a
) {
Object
[]
r
=
a
;
Node
<
K
,
V
>[]
tab
;
int
idx
=
0
;
if
(
size
>
0
&& (
tab
=
table
) !=
null
) {
for
(
Node
<
K
,
V
>
e
:
tab
) {
for
(;
e
!=
null
;
e
=
e
.
next
) {
r
[
idx
++] =
e
.
key
;
}
}
}
return
a
;
}
/**
* Fills an array with this map values and returns it. This method assumes
* that input array is big enough to fit all the values. Use
* {@link #prepareArray(Object[])} to ensure this.
*
* @param a an array to fill
* @param <T> type of array elements
* @return supplied array
*/
<
T
>
T
[]
valuesToArray
(
T
[]
a
) {
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