Final answer:
The default equals method in Java checks for reference equality, meaning it only considers two objects equal if they are the same instance in memory, not if they have the same internal state.
Step-by-step explanation:
When you do not implement an equals method for a class in Java, the class inherits the default equals method from the Object class. The default implementation of the equals method compares the memory addresses of the two objects to determine if they are the same, which is essentially a reference equality. In other words, it checks if the two references point to the exact same object in memory, not if the objects are logically "equal" by having the same internal state.
For example, consider two instances of a class Point with coordinates (x,y). Even if both instances have identical coordinates, like Point(1,2) and Point(1,2), the default equals method would consider them unequal unless they are references to the same instance.
If you want equals to perform a logical comparison, you must override it in your class, providing a specific implementation that compares relevant fields of the objects.