java 繼承示例

Prerequisite: Inheritance and its implementation in Java

先決條件： 繼承及其在Java中的實現

Java中的繼承類型 (Type of inheritance in Java)

In Java programming, there are following types of the inheritances,

在Java編程中，有以下幾種類型的繼承 ，

1. Single Inheritance

   單繼承

2. Multiple Inheritances (Through Interface)

   多重繼承(通過接口)

3. Multilevel Inheritance

   多級繼承

4. Hierarchical Inheritance

   層次繼承

1)單一繼承 (1) Single Inheritance)

If a class extends another class (i.e. the only one class).

如果一個類擴展了另一個類(即唯一一個類)。

Syntax:

句法：

    class Parent {
// Fields and Methods
}
class Child extends Parent {
// Fields and Methods
}

Example of Single Inheritance:

單一繼承的示例：

/*Java program to demonstrate the  
concept of inheritance */
// Parent class 
class Parent {
// The Parent class has one method
// displayParentMessage() method to print message of Parent Class
public void displayParentMessage() {
System.out.println("Hello, we are in parent class method");
}
}
// Sub class or derived class
class Child extends Parent {
// The Child subclass adds one more method
// displayChildMessage() method to print message of Parent Class
public void displayChildMessage() {
System.out.println("Hello, we are in child class method");
}
}
// Main class in this class we will create 
//object of parent and child class 
class Main {
public static void main(String[] args) {
// Creation of Parent class object
Parent p = new Parent();
// Calling Parent class method by Parent class object
p.displayParentMessage();
// Creation of Child class object
Child c = new Child();
// Calling Child class method by Child class object
c.displayChildMessage();
// Calling Parent class method by Child class object
c.displayParentMessage();
}
}

Output

輸出量

D:\Programs>javac Main.java
D:\Programs>java Main
Hello, we are in parent class method
Hello, we are in child class method
Hello, we are in parent class method

2)多重繼承(通過接口) (2) Multiple Inheritance (Through Interface))

If we extend more than one class. Java doesn’t support multiple inheritances directly but with the help of interface we can implement but it is similar to multiple inheritance.

如果我們擴展多個類。 Java不直接支持多重繼承，但是借助我們可以實現的接口的幫助，它類似于多重繼承。

Syntax:

句法：

    interface interface1 {
// Field and Method declaration
}
interface interface2 {
// Field and Method declaration
}
Class class_name implements interface1, interface2 {}

Example of Multiple Inheritance:

多重繼承的例子：

/*Java program to demonstrate the  
concept of multiple inheritance */
interface Print {
void print();
}
interface Show {
void show();
}
class Main implements Print, Show {
public void print() {
System.out.println("Hello");
}
public void show() {
System.out.println("World");
}
public static void main(String args[]) {
Main obj = new Main();
obj.print();
obj.show();
}
}

Output

輸出量

D:\Programs>javac Main.java
D:\Programs>java Main
Hello
World

3)多級繼承 (3) Multilevel Inheritance)

If a classA extends by classB and classB extends by classC is called multilevel inheritance.

如果將classA擴展為classB ，將classB擴展為classC，則稱為多級繼承。

Syntax:

句法：

    class classA {
// Fields and Methods
}
class classB extends classA {
// Fields and Methods
}
class classC extends classB {
// Fields and Methods
}

Example of Multilevel Inheritance:

多級繼承的示例：

/*Java program to demonstrate the  
concept of multilevel inheritance */
// ClassA class 
class ClassA {
// The ClassA class has one method
// displayClassAMessage() method to print message of ClassA Class
public void displayClassAMessage() {
System.out.println("Hello, we are in ClassA class method");
}
}
// ClassB class
class ClassB extends ClassA {
// The ClassB class adds one more method
// displayClassBMessage() method to print message of ClassB Class
public void displayClassBMessage() {
System.out.println("Hello, we are in ClassB class method");
}
}
// ClassC class
class ClassC extends ClassB {
// The ClassC class adds one more method
// displayClassCMessage() method to print message of ClassC Class
public void displayClassCMessage() {
System.out.println("Hello, we are in ClassC class method");
}
}
// Main class in this class we will create 
//object of ClassA and ClassB and ClassC class 
class Main {
public static void main(String[] args) {
// Creation of ClassA class object
ClassA ca = new ClassA();
// Calling ClassA class method by ClassA class object
ca.displayClassAMessage();
// Creation of ClassB class object
ClassB cb = new ClassB();
// Calling ClassB class method by ClassB class object
cb.displayClassBMessage();
// Calling ClassA class method by ClassB class object
cb.displayClassAMessage();
// Creation of ClassC class object
ClassC cc = new ClassC();
// Calling ClassC class method by ClassC class object
cc.displayClassCMessage();
// Calling ClassB class method by ClassC class object
cc.displayClassBMessage();
// Calling ClassA class method by ClassC class object
cc.displayClassAMessage();
}
}

Output

輸出量

D:\Programs>javac Main.java
D:\Programs>java Main
Hello, we are in ClassA class method
Hello, we are in ClassB class method
Hello, we are in ClassA class method
Hello, we are in ClassC class method
Hello, we are in ClassB class method
Hello, we are in ClassA class method

4)層次繼承 (4) Hierarchical Inheritance)

If more than one class is inherited from the base class is called hierarchical inheritance.

如果從基類繼承多個類，則稱為層次繼承。

Syntax:

句法：

    class classA {
// Fields and Methods
}
class classB extends classA {
// Fields and Methods
}
class classC extends classA {
// Fields and Methods
}

Example of Hierarchical Inheritance:

層次繼承的示例：

/*Java program to demonstrate the  
concept of hierarchical inheritance */
//ClassA
class ClassA {
// The ClassA class has one method
// displayClassAMessage() method to print message of ClassA Class
public void displayClassAMessage() {
System.out.println("Hello, we are in ClassA class method");
}
}
// ClassB class
class ClassB extends ClassA {
// The ClassB class adds one more method
// displayClassBMessage() method to print message of ClassB Class
public void displayClassBMessage() {
System.out.println("Hello, we are in ClassB class method");
}
}
// ClassC class
class ClassC extends ClassA {
// The ClassC class adds one more method
// displayClassCMessage() method to print message of ClassC Class
public void displayClassCMessage() {
System.out.println("Hello, we are in ClassC class method");
}
}
// Main class in this class we will create 
//object of ClassA and ClassB and ClassC class 
class Main {
public static void main(String[] args) {
// Creation of ClassA class object
ClassA ca = new ClassA();
// Calling ClassA class method by ClassA class object
ca.displayClassAMessage();
// Creation of ClassB class object
ClassB cb = new ClassB();
// Calling ClassB class method by ClassB class object
cb.displayClassBMessage();
// Calling ClassA class method by ClassB class object
cb.displayClassAMessage();
// Creation of ClassC class object
ClassC cc = new ClassC();
// Calling ClassC class method by ClassC class object
cc.displayClassCMessage();
// Calling ClassA class method by ClassC class object
cc.displayClassAMessage();
}
}

Output

輸出量

D:\Programs>javac Main1.java
D:\Programs>java Main1
Hello, we are in ClassA class method
Hello, we are in ClassB class method
Hello, we are in ClassA class method
Hello, we are in ClassC class method
Hello, we are in ClassA class method

翻譯自: https://www.includehelp.com/java/types-of-inheritance-in-java-with-examples.aspx

java 繼承示例