Java hashCode()

The Java.lang.Object class encompasses crucial methods, including hashCode(), which play a key role in real-time applications. Notably, the hashCode() method of Object is implemented as a native method, meaning its actual implementation does not reside solely within the Java programming language. Upon examining the source code of the Object class, one can observe the following code snippet pertaining to the hashCode() method.

public native int hashCode();

This observation highlights the fact that the hashCode method in Java provides a native implementation that, to some extent, returns the memory address. Nevertheless, it is feasible to override the hashCode method in a custom implementation class. Native methods, in general, are either intrinsic, meaning they are built-in and optimized by the Java Virtual Machine, or they are written in machine-specific "native" code outside the scope of the Java language.

The responsibility of generating a meaningful hashCode is bestowed upon the developer, as the language itself does not automatically generate one. However, the Object class in Java generates a default hashCode based on the memory address of the object instance. It is crucial, especially for classes within the Collection API, to implement their own hashCode method (along with the equals method) to ensure proper functionality.

It is important to note that the value returned by hashCode() is not guaranteed to be the actual memory address of the object. According to the Java API, the calculation of hashCode is based on the 32-bit internal address within the Java Virtual Machine (JVM) for the object. Although the object may move in memory during execution, the hashcode remains constant.

Student student1 = new Student(); person1.setName("John"); Student student2 = new Student(); person2.setName("Doe"); Student student3 = student2;

In the above case, student1.hashCode will not be equal to student2.hashCode because the memory addresses of these two objects are not the same. But student2.hashCode will be equal to student3 because they are pointing to the same object . So if you need to use hashCode method for your objects you must implement it yourself.