Object-Oriented Programming

A mutator method, commonly known as a setter, is used to modify the state of an object by changing the value of its private fields.

Having multiple constructors is called constructor overloading. It is perfectly valid as long as the constructors have different parameter lists (different signatures).

Polymorphism allows objects to be treated as instances of their parent class, enabling different classes to provide their own specific implementation of a method defined in a common interface or superclass.

The 'private' access modifier restricts visibility so that the member can only be accessed within the class where it is declared.

Encapsulation is the bundling of data and methods that operate on that data into a single unit, and restricting direct access to some of the object's components to protect the internal state.

A dependency represents a temporary relationship where one class uses another class, often as a parameter in a method or a local variable.

Aggregation represents a 'has-a' relationship where one class contains another, but the contained object can exist independently of the container.

Garbage collection in Java is an automatic memory management process that identifies and discards objects that are no longer needed by the application, thereby freeing up memory resources. This prevents memory leaks without requiring manual de-allocation by the developer.

In the Java Collections Framework, java.util.Map is a self-contained interface that models key-value mappings and does not extend the java.util.Collection interface. In contrast, List, Set, and Queue all extend Collection.

java.util.Collections is a utility class in Java that consists entirely of static methods that operate on or return collections (such as sorting, searching, or making them thread-safe). The interface that collection classes implement is java.util.Collection (singular).

In Java, you can declare a class as abstract even if it contains only concrete methods (methods with implementations) and no abstract methods. This is typically done to prevent the class from being instantiated directly, forcing users to subclass it.

Private members of a class are only accessible within the class in which they are declared. Even though a subclass inherits all members of its superclass, it cannot directly access private fields or methods. Instead, it must use public or protected getter and setter methods to interact with them.

Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. The overriding method must have the exact same name, return type, and parameter list (signature) as the method in the parent class. This allows for runtime polymorphism.

The Serializable interface is a marker interface, which means it does not contain any methods or fields. Since there are no methods defined in the interface, a class that implements Serializable does not need to implement any methods.