java.util.HashMap<K, V>
HashMap is an implementation of Map. All optional operations are supported,
adding and removing. Keys and values can be any objects.
Known Direct Subclasses
Summary
Public Constructors
Public Methods
clear,
clone,
containsKey,
containsValue,
entrySet,
equals,
get,
hashCode,
isEmpty,
keySet,
put,
putAll,
remove,
size,
toString,
values
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait
Methods inherited
from interface
java.util.Map
clear,
containsKey,
containsValue,
entrySet,
equals,
get,
hashCode,
isEmpty,
keySet,
put,
putAll,
remove,
size,
values
Details
Public Constructors
public
HashMap()
Constructs a new empty instance of HashMap.
public
HashMap(int capacity)
Constructs a new instance of HashMap with the specified capacity.
Parameters
capacity
| the initial capacity of this HashMap |
public
HashMap(int capacity, float loadFactor)
Constructs a new instance of HashMap with the specified capacity and load
factor.
Parameters
capacity
| the initial capacity |
loadFactor
| the initial load factor |
public
HashMap(Map<? extends K, ? extends V> map)
Constructs a new instance of HashMap containing the mappings from the
specified Map.
Public Methods
public
void
clear()
Removes all mappings from this HashMap, leaving it empty.
public
Object
clone()
Returns a new HashMap with the same mappings and size as this HashMap.
Returns
- a shallow copy of this HashMap
public
boolean
containsKey(Object key)
Searches this HashMap for the specified key.
Parameters
key
| the object to search for |
Returns
- true if
key
is a key of this HashMap, false
otherwise
public
boolean
containsValue(Object value)
Searches this HashMap for the specified value.
Parameters
value
| the object to search for |
Returns
- true if
value
is a value of this HashMap, false
otherwise
public
Set<Entry<K, V>>
entrySet()
Returns a Set of the mappings contained in this HashMap. Each element in
the set is a Map.Entry. The set is backed by this HashMap so changes to
one are reflected by the other. The set does not support adding.
public
V
get(Object key)
Returns the value of the mapping with the specified key. If no entry is
found null is returned.
Returns
- the value of the mapping with the specified key, or null if the
entry doesn't exist.
public
boolean
isEmpty()
Returns if this HashMap has no elements, a size of zero.
Returns
- true if this HashMap has no elements, false otherwise
public
Set<K>
keySet()
Returns a Set of the keys contained in this HashMap. The set is backed by
this HashMap so changes to one are reflected by the other. The set does
not support adding.
public
V
put(K key, V value)
Maps the specified key to the specified value.
Parameters
key
| the key |
value
| the value |
Returns
- the value of any previous mapping with the specified key or null
if there was no mapping
public
void
putAll(Map<? extends K, ? extends V> map)
Copies all the mappings in the given map to this map. These mappings will
replace all mappings that this map had for any of the keys currently in
the given map.
Parameters
map
| the Map to copy mappings from |
public
V
remove(Object key)
Removes a mapping with the specified key from this HashMap.
Parameters
key
| the key of the mapping to remove |
Returns
- the value of the removed mapping or null if key is not a key in
this HashMap
public
int
size()
Returns the number of mappings in this HashMap.
Returns
- the number of mappings in this HashMap
Returns a Collection of the values contained in this HashMap. The
collection is backed by this HashMap so changes to one are reflected by
the other. The collection does not support adding.
Returns
- a Collection of the values