What are parent classes and subclasses in java

Parent class and subclass: Parent class: Base class, defining shared characteristics and behaviors. Subclass: Derived class, inherits the parent class and extends the functionality. is-a relationship: subclass "is-a" parent class. Inheritance: Subclasses inherit non-private members of the parent class. Method overriding: Subclasses can override parent class methods to provide different implementations. Polymorphism: Parent class references can point to subclass objects.

Parent class and subclass in Java

In Java, the inheritance relationship between classes follows " is-a" principle. The parent class defines the common characteristics and behaviors of the subclass, and the subclass inherits and extends the functionality of the parent class.

What is a parent class?

The parent class is a base class that contains properties and methods shared by subclasses. Subclasses can inherit the fields, methods, and constructors of the parent class. Parent classes cannot inherit methods or fields from subclasses.

What is a subclass?

A subclass is a derived class that extends the functionality of the parent class. A subclass inherits all members of the parent class and can add additional members of its own. Subclasses can override parent class methods to provide different implementations.

The relationship between parent class and subclass

• "is-a" relationship: Subclass "is-a" parent class . For example, if Animal is the parent class and Dog is the subclass, then Dog "is-a" Animal.
• Inheritance: The subclass inherits all non-private members of the parent class.
• Method override: Subclasses can override parent class methods to provide different implementations.
• Polymorphism: References from parent classes can point to objects of subclasses. This makes the code flexible since it can handle collections of different types of objects.

Example

Consider the following code example:

<code class="java">class Animal {
    private String name;
    public Animal(String name) { this.name = name; }
    public String getName() { return name; }
}

class Dog extends Animal {
    private String breed;
    public Dog(String name, String breed) { super(name); this.breed = breed; }
    public String getBreed() { return breed; }
}</code>

In the example, Animal is the parent class,Dog is a subclass. Dog inherits Animal's name field and getName() method, and adds its own breed fields and the getBreed() method.

By using inheritance, we can create a hierarchy that is more reusable and less expensive to maintain.

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