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--- public:t-622-arti-13-1:lab_3_-_hashing_states [2013/02/07 11:07] – [Material] stephan
+++ public:t-622-arti-13-1:lab_3_-_hashing_states [2024/04/29 13:33] (current) – external edit 127.0.0.1
@@ Line 10: / Line 10: @@
 ===== Material =====
-  * {{:public:t-622-arti-13-1:hashing_states.zip123|java project for the lab}}
+  * {{:public:t-622-arti-13-1:hashing_states.zip|java project for the lab}}
 The project contains a State class that could be thought of implementing a state of some robot. The state consists of a position, an orientation and a boolean holding the information of whether or not the robot is turned on. The project also contains code to test how good the hashCode() method of the State class is. To run the tests simply run the Main class or use "ant run" on the terminal.
+===== Hints =====
+  * You need to implement the methods [[http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html#hashCode%28%29|int hashCode()]] and [[http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html#equals%28java.lang.Object%29|boolean equals(Object o)]] in classes State and Position appropriately.
+  * For two states ''s1'' and ''s2'' that you'd consider the same, ''s1.equals(s2)'' must return true and false otherwise.
+  * For any two objects ''o1'' and ''o2'', if ''o1.equals(o2)'' then ''o1.hashCode() == o2.hashCode()'' must be true!
+  * Objects that are not equal are allowed have the same hash code. However, if that happens too often then hash maps become very inefficient.
 ===== Handing In =====