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I am creating a many-to-many mapping of two object classes. Do I need to write hashCode() and equals() methods; if so, does the netbeans automatically generated code help?
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Both methods, equals() and hashcode() , are used in Hashtable , for example, to store values as key-value pairs. If we override one and not the other, there is a possibility that the Hashtable may not work as we want, if we use such object as a key. Save this answer.
General contract associated with hashCode() methodIf two objects are equal(according to equals() method) then the hashCode() method should return the same integer value for both the objects.
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 equals(java. lang.
if a class overrides equals, it must override hashCode. when they are both overridden, equals and hashCode must use the same set of fields. if two objects are equal, then their hashCode values must be equal as well. if the object is immutable, then hashCode is a candidate for caching and lazy initialization.
Yes it can!
Simply right click within the class where the objects have been created and choose insert code. A small menu titled "Generate" will pop up with various options, among them is equals() and hashCode(), select it and presto, NetBeans generates the code override for you. Test out the equals method and it will work this time.
NB. When you select "equals() and hashCode()" a Dialogue box appears, just check the boxes on both sides for all the variables you want dealt with. See the image below:
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answered Oct 16 '22 07:10
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