What Is The HashCode () And Equals () Used For?

What is hashCode and how it works?

Simply put, hashCode() returns an integer value, generated by a hashing algorithm.

Objects that are equal (according to their equals()) must return the same hash code.

It’s not required for different objects to return different hash codes..

What is meant by Hashcode?

Answer: The hashcode of a Java Object is simply a number, it is 32-bit signed int, that allows an object to be managed by a hash-based data structure. We know that hash code is an unique id number allocated to an object by JVM. … If two objects are equals then these two objects should return same hash code.

What is difference between == equals () and compareTo () method?

equals() checks if two objects are the same or not and returns a boolean. compareTo() (from interface Comparable) returns an integer. It checks which of the two objects is “less than”, “equal to” or “greater than” the other. … Note that equals() doesn’t define the ordering between objects, which compareTo() does.

Is HashMap thread safe?

HashMap is non synchronized. It is not-thread safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. It is thread-safe and can be shared with many threads.

What is hashCode () in Java?

A hash code is an integer value that is associated with each object in Java. Its main purpose is to facilitate hashing in hash tables, which are used by data structures like HashMap.

What is the difference between hashCode and equals?

equals() and hashCode() are different methods and hashCode method should not be used to check if two object references are same. … The value returned by hashCode() is the object’s hash code, which is the object’s memory address in hexadecimal. equals() checks if the two object references are same.

How is hashCode calculated?

Steps:Calculate hashCode of Key {“sachin”}. It will be generated as 115.Calculate index by using index method it will be 3.Create a node object as : { int hash = 115 Key key = {“sachin”} Integer value = 30 Node next = null }

Can 2 objects have same Hashcode?

It is perfectly legal for two objects to have the same hashcode. If two objects are equal (using the equals() method) then they have the same hashcode.

Can two string have same hashCode?

Yes, it is possible for two Strings to have the same hashcode – If you take a look at the Wikipedia article, you will see that both “FB” and “Ea” have the same hashcode. There is nothing in the method contract saying a hashCode() should be used to compare for equality, you want to use equals() for that.

What is the importance of hashCode () and equals () methods?

Java hashCode() An object hash code value can change in multiple executions of the same application. If two objects are equal according to equals() method, then their hash code must be same. If two objects are unequal according to equals() method, their hash code are not required to be different.

What is the purpose of the hashCode () method?

The purpose of the hashCode() method is to provide a numeric representation of an object’s contents so as to provide an alternate mechanism to loosely identify it. By default the hashCode() returns an integer that represents the internal memory address of the object.

How do I override Hashcode?

Overriding hashCode method in Java Take a prime hash e.g. 5, 7, 17 or 31 (prime number as hash, results in distinct hashcode for distinct object) Take another prime as multiplier different than hash is good. Compute hashcode for each member and add them into final hash. … Return hash.