HashCode and Equals method in Java

In the Java programming language, each object is endowed with access to the equals() method as it is inherited from the Object class. Should two objects be deemed equal in accordance with the equals(Object) method, invoking the hashCode method on each of the two objects must invariably yield an identical integer result. It is imperative to override the hashCode() method in any class that overrides equals(). Failure to do so will infringe upon the fundamental contract stipulated by Object.hashCode(), consequently impeding the proper functioning of your class in conjunction with various hash-based collections such as HashMap, HashSet, and Hashtable.

Should you opt not to override hashCode(), the default implementation provided by the Object class will be utilized by collections. Regrettably, this default implementation assigns distinct hash values to distinct objects, even if they are deemed equal based on the equals() method. This discrepancy poses a significant predicament, as it undermines the expected behavior of hash-based collections, potentially leading to erroneous and inconsistent results.


The hashcode() method in Java serves the purpose of generating a hash code specifically tailored for a given string. This hash code holds significant relevance within hash-based data structures, such as HashMap, HashTable, HashSet, and others. Its primary application lies in the process of bucketing, wherein elements are organized and stored based on their respective hash codes.

The value derived from invoking hashCode() on an object acts as the designated bucket number, serving as a unique identifier for storing elements within the set or map. In essence, this bucket number serves as the address or location of the element within the data structure.

Using the hashCode() value as the bucket number, these hash-based implementations efficiently distribute and categorize elements, optimizing storage and retrieval operations. This mechanism enables faster access to elements, as the data structure can swiftly identify the specific bucket corresponding to the hash code, thus reducing search complexities and enhancing overall performance.


The purpose of the equals() method in Java is to facilitate the comparison of equality between two objects. In the Java programming language, there exist two distinct approaches for performing comparisons: one involves utilizing the "==" operator, while the other involves utilizing the equals() method.

The "==" operator compares the object references themselves, determining whether they refer to the exact same memory location. This comparison is purely based on the reference values and does not consider the internal state or content of the objects.

On the other hand, the equals() method enables a more sophisticated and customizable comparison. It allows for a logical evaluation of equality based on the specific implementation provided within the class. By overriding the equals() method, developers can define their own equality criteria, taking into account the object's internal state or content.


The equals() method should be used when comparing the semantic equality of objects, as it allows for a more nuanced assessment. The "==" operator, on the other hand, should be employed when comparing object references themselves, solely focusing on their identity in memory.