it is the base class of all the classes in java
Methods in Java Object class
- hashCode:
- the more unique the hashCode is the more efficient is the hash map/table
- used to find the bucket in which an object goes into in a hash table.
- more than one invocation of hashCode of the same object should return same Integer.
- if two objects are equal according to equals method then their hashCode must be same.
- equals:
- is used in hashMap when two objects have same hashCode.
- if two objects are equal their hashCode must be same.
- it should be
- reflexive : x.equals(x)
- symmetric: x.equals(y) and y.equals(x)
- transtive: x.equals(y) y.equals(z) implies => x.equals(z)
- consitent: x.equals(y) should allways return same value.
- for null it should be false: x.equals(null) false
- the default behaviour of equals = “==” i.e is object comparision
- toString :
- the default implementation is
- classname @ hex format of the hashCode.
- its good to override toString .
- also should be concise and informative.
- clone:
- to clone the object .
- x.clone() != x
- x.clone().getClass() == x.getClass() Not mandatory *
- x.clone().equals(x) Not mandatory *
- alternative to clone is copy constructor
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