Returns a hash code value for the object. This method is
supported for the benefit of hashtables such as those provided by
The general contract of hashCode is:
Whenever it is invoked on the same object more than once during
an execution of a Java application, the hashCode method
must consistently return the same integer, provided no information
used in equals comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
If two objects are equal according to the equals(Object)
method, then calling the hashCode method on each of
the two objects must produce the same integer result.
It is not required that if two objects are unequal
according to the Object.equals(java.lang.Object)
method, then calling the hashCode method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hashtables.
As much as is reasonably practical, the hashCode method defined by
class Object does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
JavaTM programming language.)
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