类 AbstractMap<K,V>
- 所有已实现的接口:
Map<K,V>
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嵌套类概要
嵌套类修饰符和类型类说明static classAn Entry maintaining a key and a value.static classAn Entry maintaining an immutable key and value. -
构造器概要
构造器 -
方法概要
修饰符和类型方法说明voidclear()protected Objectclone()Returns a shallow copy of this AbstractMap instance: the keys and values themselves are not cloned.booleancontainsKey(Object key) booleancontainsValue(Object value) entrySet()booleanCompares the specified object with this map for equality.inthashCode()Returns the hash code value for this map.booleanisEmpty()keySet()voidintsize()toString()Returns a string representation of this map.values()从接口继承的方法 java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll
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构造器详细资料
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AbstractMap
protected AbstractMap()Sole constructor. (For invocation by subclass constructors, typically implicit.)
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方法详细资料
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size
public int size()This implementation returns entrySet().size().
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isEmpty
public boolean isEmpty()This implementation returns size() == 0.
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containsValue
This implementation iterates over entrySet() searching for an entry with the specified value. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map.
- 指定者:
containsValue在接口中Map<K,V> - 抛出:
ClassCastExceptionNullPointerException
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containsKey
This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.
- 指定者:
containsKey在接口中Map<K,V> - 抛出:
ClassCastExceptionNullPointerException
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get
This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, the entry's value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.
- 指定者:
get在接口中Map<K,V> - 抛出:
ClassCastExceptionNullPointerException
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put
This implementation always throws an UnsupportedOperationException.
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remove
This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, its value is obtained with its getValue operation, the entry is removed from the collection (and the backing map) with the iterator's remove operation, and the saved value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.
Note that this implementation throws an UnsupportedOperationException if the entrySet iterator does not support the remove method and this map contains a mapping for the specified key.
- 指定者:
remove在接口中Map<K,V> - 抛出:
UnsupportedOperationExceptionClassCastExceptionNullPointerException
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putAll
This implementation iterates over the specified map's entrySet() collection, and calls this map's put operation once for each entry returned by the iteration.
Note that this implementation throws an UnsupportedOperationException if this map does not support the put operation and the specified map is nonempty.
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clear
public void clear()This implementation calls entrySet().clear().
Note that this implementation throws an UnsupportedOperationException if the entrySet does not support the clear operation.
- 指定者:
clear在接口中Map<K,V> - 抛出:
UnsupportedOperationException
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keySet
This implementation returns a set that subclasses {link AbstractSet}. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsKey method.
The set is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same set.
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values
This implementation returns a collection that subclasses
AbstractCollection. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsValue method.The collection is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same collection.
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entrySet
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equals
Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). This ensures that the equals method works properly across different implementations of the Map interface.This implementation first checks if the specified object is this map; if so it returns true. Then, it checks if the specified object is a map whose size is identical to the size of this map; if not, it returns false. If so, it iterates over this map's entrySet collection, and checks that the specified map contains each mapping that this map contains. If the specified map fails to contain such a mapping, false is returned. If the iteration completes, true is returned.
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hashCode
public int hashCode()Returns the hash code value for this map. The hash code of a map is defined to be the sum of the hash codes of each entry in the map's entrySet() view. This ensures that m1.equals(m2) implies that m1.hashCode()==m2.hashCode() for any two maps m1 and m2, as required by the general contract ofObject.hashCode().This implementation iterates over entrySet(), calling
hashCode()on each element (entry) in the set, and adding up the results. -
toString
Returns a string representation of this map. The string representation consists of a list of key-value mappings in the order returned by the map's entrySet view's iterator, enclosed in braces ("{}"). Adjacent mappings are separated by the characters ", " (comma and space). Each key-value mapping is rendered as the key followed by an equals sign ("=") followed by the associated value. Keys and values are converted to strings as byString.valueOf(Object). -
clone
Returns a shallow copy of this AbstractMap instance: the keys and values themselves are not cloned.- 覆盖:
clone在类中Object- 返回:
- a shallow copy of this map
- 抛出:
CloneNotSupportedException
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