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1. If two objects are equal, then they must have the same hash code.
2. If two objects have the same hashcode, they may or may not be equal.
The idea behind a Map is to be able to find an object faster than a linear search. Using hashed keys to locate objects is a two-step process. Internally the Map stores objects as an array of arrays. The index for the first array is the hashcode() value of the key. This locates the second array which is searched linearly by using equals() to determine if the object is found.
The default implementation of hashCode() in Object class returns distinct integers for different objects. Therefore, in the example above, different objects(even with same type) have different hashCode
In this example, a green apple object is stored successfully in a hashMap, but when the map is asked to retrieve this object, the apple object is not found.