How is the hashCode value of an object calculated if not overridden manually?

If the hashCode() method is not overridden manually, then by default in Java (and thus in Android), it is inherited from the Object class. In this case, the hashCode value is usually based on the internal address of the object in memory or on some unique identifier assigned to the object by the JVM at creation. This means that two different objects will have different hash codes, even if their contents are the same.

Example:

Object obj1 = new Object();
Object obj2 = new Object();
System.out.println(obj1.hashCode()); // for example, 12345678
System.out.println(obj2.hashCode()); // for example, 87654321

If you want objects with the same data to have the same hashCode, you need to override this method.