what is hashcode and equals contract?

[varinder mahajan]

what is hashcode and equals contract?

[marc weber]

This is described in the API, under java.lang.Object's hashCode() method.

[Mario Razec]

hi...
I understand that:

equals() using to comparison, refers to equivalence relations.
hashCode() is id number allocated to an object by JVM.
Contract: When you use equals() and hashCode() methods is necessary to override these methods

But checking please:
https://coderanch.com/t/269570/java-programmer-SCJP/certification/Let-discuss-hashcode-contract

http://www.javaworld.com/community/?q=node/1006
http://java.sun.com/developer/Books/effectivejava/Chapter3.pdf

[arulk pillai]

The key thing to remember is that:

-- If two objects are equal then they should have the same hascode but the reverse is not true (i.e. If two objects have the same hashcode does not mean that they are equal)

-- You need to use the same attributes in your equals & hashCode methods


Look at the doco for further info.

[Sandeep Bhandari]

Besides checking about the implications of equals and hashcode values, the exam may simply ask that if you implement equals() method, which other method you should implement?