What keywords are used for class inheritance in java

The extends keyword is used in Java to implement class inheritance. The subclass inherits the non-private members of the parent class and can extend, override or call the parent class method. The advantages of inheritance include code reuse, extensibility, and polymorphism, but care needs to be taken to ensure that inheritance relationships are reasonable, to avoid excessive inheritance, and to pay attention to access permissions.

Inheritance of classes in Java

The extends keyword is used in Java to implement classes inheritance.

The mechanism of inheritance

When a class inherits another class, it is called a subclass or derived class, and the inherited class is called a base class or parent class . Subclasses inherit properties and methods from parent classes.

Characteristics of subclasses

• The subclass has all non-private members of the parent class: The subclass can access and use the parent class All public, protected, and default (package) members of .
• Subclasses can extend parent classes: Subclasses can add new member variables, methods or override parent class methods.
• Subclasses can override methods of parent classes: Subclasses can override methods of parent classes by redeclaring them with the same signature and providing new implementations.
• Subclasses can call methods of parent classes: Subclasses can access and call methods of parent classes by using the super keyword.
• The object of the subclass is a subtype of the parent class object: The object of the subclass can be assigned to the variable of the parent class, and can be passed as a parameter of the parent class.

Advantages of inheritance

• Code reuse: Inheritance allows subclasses to reuse code in parent classes, reducing duplicate code and maintenance costs.
• Extensibility: Inheritance provides a convenient way to create new classes that extend the functionality of existing classes.
• Polymorphism: Inheritance supports polymorphism, allowing subclass objects to be treated as parent class objects, thereby enabling different objects to be processed in the same way.

Notes on inheritance

• Ensure the rationality of the inheritance relationship: Ensure that it makes sense for the subclass to inherit the parent class , and the subclass extends the parent class rather than duplicating its functionality.
• Avoid over-inheritance: Avoid creating too many layers of inheritance hierarchies, as this increases complexity and makes maintenance difficult.
• Note access permissions: Subclasses can only access non-private members of the parent class, so ensure that the parent class's members have appropriate visibility.

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