Can two hash codes be equal?
Can two hash codes be equal?
If two objects have the same hashcode then they are NOT necessarily equal. Otherwise you will have discovered the perfect hash function. But the opposite is true: if the objects are equal, then they must have the same hashcode .
Can hashCode of two objects be same in Java?
If two objects are equal, they MUST have the same hash code. If two objects have the same hash code, it doesn’t mean that they are equal. Overriding equals() alone will make your business fail with hashing data structures like: HashSet, HashMap, HashTable etc.
What is the difference between hash code and equals?
hashCode() does not return the object’s reference, but a hash of the object, computed in some way. equals(obj2) is true then obj1. hasCode() must be true to be a valid implementation. Reason: hashCode just returns int value for an Object, even two different objects can have same hashCode integer.
How are hash codes generated?
However, Object generates a HashCode based on the memory address of the instance of the object. According to Java API, the calculation of hashcode is based on 32-bit internal JVM (Java Virtual Machine) address of the Object. It is true that the object moves during execution. But hashcode does not change.
What is the hashcode () and equals () used for?
1. Uses of hashCode() and equals() Methods. equals(Object otherObject) – verifies the equality of two objects. Its default implementation simply checks the object references of two objects to verify their equality.
What is the use of hash code?
hashCode() is used for bucketing in Hash implementations like HashMap , HashTable , HashSet , etc. The value received from hashCode() is used as the bucket number for storing elements of the set/map. This bucket number is the address of the element inside the set/map.
Where are hashCode and equals methods defined in Java?
hashCode() and equals() methods have been defined in Object class which is parent class for java objects. For this reason, all java objects inherit a default implementation of these methods.
Is there a contract for hashCode in Java?
Java SE also defines a contract for the hashCode () method. A thorough look at it shows how closely related hashCode () and equals () are. All three criteria in the contract of hashCode () mention in some ways the equals () method:
How does equals ( null ) work in Java?
For any object x, the equals (null) must return false. A hashcode is an integer value associated with every object in Java, facilitating the hashing in hash tables. To get this hashcode value for an object, we can use the hashcode () method in Java. It is the means hashcode () method that returns the integer hashcode value of the given object.
When does hashCode return the same hash value?
The hashcode () method returns the same hash value when called on two objects, which are equal according to the equals () method. And if the objects are unequal, it usually returns different hash values.