- All Known Implementing Classes:AbstractMap.SimpleEntry, AbstractMap.SimpleImmutableEntryEnclosing interface:Map<K,V>
public static interface Map.Entry<K,V>A map entry (key-value pair). The
Map.entrySetmethod returns a collection-view of the map, whose elements are of this class. The only way to obtain a reference to a map entry is from the iterator of this collection-view. These
Map.Entryobjects are valid only for the duration of the iteration; more formally, the behavior of a map entry is undefined if the backing map has been modified after the entry was returned by the iterator, except through the
setValueoperation on the map entry.
Since: 1.2See Also:Map.entrySet()
Method Summary
All Methods Static Methods Instance Methods Abstract Methods Default MethodsModifier and Type Method and Description static <K extends Comparable<? super K>,V>
Comparator<Map.Entry<K,V>>comparingByKey() Returns a comparator that compares Map.Entry in natural order on key.
static <K,V> Comparator<Map.Entry<K,V>> comparingByKey(Comparator<? super K> cmp) Returns a comparator that compares Map.Entry by key using the given Comparator.
static <K,V extends Comparable<? super V>>
Comparator<Map.Entry<K,V>>comparingByValue() Returns a comparator that compares Map.Entry in natural order on value.
static <K,V> Comparator<Map.Entry<K,V>> comparingByValue(Comparator<? super V> cmp) Returns a comparator that compares Map.Entry by value using the given Comparator.
boolean equals(Object o) Compares the specified object with this entry for equality.
K getKey() Returns the key corresponding to this entry.
V getValue() Returns the value corresponding to this entry.
int hashCode() Returns the hash code value for this map entry.
V setValue(V value) Replaces the value corresponding to this entry with the specified value (optional operation).
Method Detail
getKey
K getKey()Returns the key corresponding to this entry.
Returns:the key corresponding to this entryThrows:IllegalStateException - implementations may, but are not required to, throw this exception if the entry has been removed from the backing map.
getValue
V getValue()Returns the value corresponding to this entry. If the mapping has been removed from the backing map (by the iterator's
removeoperation), the results of this call are undefined.
Returns:the value corresponding to this entryThrows:IllegalStateException - implementations may, but are not required to, throw this exception if the entry has been removed from the backing map.
setValue
V setValue(V value)Replaces the value corresponding to this entry with the specified value (optional operation). (Writes through to the map.) The behavior of this call is undefined if the mapping has already been removed from the map (by the iterator's
removeoperation).
Parameters:value - new value to be stored in this entryReturns:old value corresponding to the entryThrows:UnsupportedOperationException - if the put operation is not supported by the backing mapClassCastException - if the class of the specified value prevents it from being stored in the backing mapNullPointerException - if the backing map does not permit null values, and the specified value is nullIllegalArgumentException - if some property of this value prevents it from being stored in the backing map IllegalStateException - implementations may, but are not required to, throw this exception if the entry has been removed from the backing map.
equals
boolean equals(Object o)Compares the specified object with this entry for equality. Returns
trueif the given object is also a map entry and the two entries represent the same mapping. More formally, two entries
e1and
e2represent the same mapping if
(e1.getKey()==null ? e2.getKey()==null : e1.getKey().equals(e2.getKey())) && (e1.getValue()==null ? e2.getValue()==null : e1.getValue().equals(e2.getValue()))This ensures that the
method works properly across different implementations of the
Map.Entryinterface.
Overrides:equals in class ObjectParameters:o - object to be compared for equality with this map entryReturns:true if the specified object is equal to this map entrySee Also: Object.hashCode(), HashMap
hashCode
int hashCode()Returns the hash code value for this map entry. The hash code of a map entry
eis defined to be:
(e.getKey()==null ? 0 : e.getKey().hashCode()) ^ (e.getValue()==null ? 0 : e.getValue().hashCode())This ensures that
e1.equals(e2)implies that
e1.hashCode()==e2.hashCode()for any two Entries
e1and
e2, as required by the general contract of
Object.hashCode.
Overrides:hashCode in class ObjectReturns:the hash code value for this map entrySee Also:Object.hashCode(), Object.equals(Object), equals(Object)
comparingByKey
static <K extends Comparable<? super K>,V> Comparator<Map.Entry<K,V>> comparingByKey()Returns a comparator that compares Map.Entry in natural order on key.
The returned comparator is serializable and throws NullPointerException when comparing an entry with a null key.
Type Parameters:K - the Comparable type of then map keysV - the type of the map valuesReturns:a comparator that compares Map.Entry in natural order on key.Since:1.8See Also:Comparable
comparingByValue
static <K,V extends Comparable<? super V>> Comparator<Map.Entry<K,V>> comparingByValue()Returns a comparator that compares Map.Entry in natural order on value.
The returned comparator is serializable and throws NullPointerException when comparing an entry with null values.
Type Parameters:K - the type of the map keysV - the Comparable type of the map valuesReturns: a comparator that compares Map.Entry in natural order on value.Since:1.8See Also:Comparable
comparingByKey
static <K,V> Comparator<Map.Entry<K,V>> comparingByKey(Comparator<? super K> cmp)Returns a comparator that compares Map.Entry by key using the given Comparator.
The returned comparator is serializable if the specified comparator is also serializable.
Type Parameters: K - the type of the map keysV - the type of the map valuesParameters:cmp - the key ComparatorReturns:a comparator that compares Map.Entry by the key.Since:1.8
comparingByValue
static <K,V> Comparator<Map.Entry<K,V>> comparingByValue(Comparator<? super V> cmp)Returns a comparator that compares Map.Entry by value using the given Comparator.
The returned comparator is serializable if the specified comparator is also serializable.
Type Parameters:K - the type of the map keysV - the type of the map valuesParameters:cmp - the value ComparatorReturns:a comparator that compares Map.Entry by the value.Since:1.8
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