A map entry (key-value pair). The Map.entrySet method 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.Entry objects 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 setValue operation on the map entry.
@since
1.2
See Also
Map#entrySet()
Compares the specified object with this entry for equality. Returns true if the given object is also a map entry and the two entries represent the same mapping. More formally, two entries e1 and e2 represent 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 equals method works properly across different implementations of the Map.Entry interface.
Parameters
oobject to be compared for equality with this map entry.
Return
true if the specified object is equal to this map entry.
Returns the key corresponding to this entry.
Return
the key corresponding to this entry.
Throws
IllegalStateExceptionimplementations may, but are not required to, throw this exception if the entry has been removed from the backing map
Returns the value corresponding to this entry. If the mapping has been removed from the backing map (by the iterator's remove operation), the results of this call are undefined.
Return
the value corresponding to this entry.
Throws
IllegalStateExceptionimplementations may, but are not required to, throw this exception if the entry has been removed from the backing map
Returns the hash code value for this map entry. The hash code of a map entry e is 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 e1 and e2, as required by the general contract of Object.hashCode.
Return
the hash code value for this map entry.
See Also
Object#hashCode() , Object#equals(Object) , #equals(Object)
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 remove operation).
Parameters
valuenew value to be stored in this entry.
Return
old value corresponding to the entry.
Throws
UnsupportedOperationExceptionif the put operation is not supported by the backing map.
ClassCastExceptionif the class of the specified value prevents it from being stored in the backing map.
IllegalArgumentExceptionif some aspect of this value prevents it from being stored in the backing map.
NullPointerExceptionif the backing map does not permit null values, and the specified value is null.
IllegalStateExceptionimplementations may, but are not required to, throw this exception if the entry has been removed from the backing map