Introduction to inherited features and keywords

Inherited features:

(Recommended tutorial: java introductory tutorial)

• Subclass Possess non-private properties and methods of the parent class.

• Subclasses can have their own properties and methods, that is, subclasses can extend parent classes.

• Subclasses can implement the methods of the parent class in their own way.

• Java's inheritance is single inheritance, but it can be multiple inheritance. Single inheritance means that a subclass can only inherit one parent class. Multiple inheritance means, for example, class A inherits class B, and class B Inherit class C, so according to the relationship, class C is the parent class of class B, and class B is the parent class of class A. This is a feature that distinguishes Java inheritance from C inheritance.

• Improves the coupling between classes (the disadvantage of inheritance is that high coupling will cause the closer the connection between codes and the worse the code independence).

Keywords:

Inheritance can be achieved using the two keywords extends and implements, and all classes inherit from java.lang .Object, when a class does not inherit the two keywords, it inherits the object ancestor class by default (this class is in the java.lang package, so there is no need to import).

extends keyword

In Java, class inheritance is single inheritance, that is to say, a subclass can only have one parent class, so extends can only inherit one class.

Example:

public class Animal { 
    private String name;   
    private int id; 
    public Animal(String myName, String myid) { 
        //初始化属性值
    } 
    public void eat() {  
        //吃东西方法的具体实现  
    } 
    public void sleep() { 
        //睡觉方法的具体实现  
        }
    } 
    public class Penguin  extends  Animal{ 

}

(Video tutorial recommendation: java course)

implements keyword

Use the implements keyword in disguise Java has the feature of multiple inheritance. When a class inherits an interface, it can inherit multiple interfaces at the same time (the interfaces are separated by commas).

public interface A {
    public void eat();    
    public void sleep();
}
public interface B {
    public void show();
}
public class C implements A,B {
}

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