java的HashMap类提供的方法

voidclear()

Removes all of the mappings from this map.

Objectclone()

Returns a shallow copy of this HashMap instance: the keys and values themselves are not cloned.

booleancontainsKey(Object key)

Returns true if this map contains a mapping for the specified key.

booleancontainsValue(Object value)

Returns true if this map maps one or more keys to the specified value.

Set<Map.Entry<K,V>>entrySet()  返回一个包含HashMap的键值对的set

Returns a Set view of the mappings contained in this map.

Vget(Object key) 根据键获取值

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

booleanisEmpty() 

Returns true if this map contains no key-value mappings.

Set<K>keySet() 返回一个HashMap键的Set

Returns a Set view of the keys contained in this map.

Vput(K key, V value)

Associates the specified value with the specified key in this map.

voidputAll(Map<? extends K,? extends V> m)

Copies all of the mappings from the specified map to this map.

Vremove(Object key) 根据键移除

Removes the mapping for the specified key from this map if present.

intsize()

Returns the number of key-value mappings in this map.

Collection<V>values() 返回一个HashMap的值的Collection

Returns a Collection view of the values contained in this map.