


Java inheritance, whether the subclass inherits the constructor of the parent class
In inheritance in java, whether the subclass inherits the constructor of the parent class
In inheritance in java, the subclass will not inherit the constructor of the parent class, but it must call (Implicit or explicit)
Let’s look at the example:
public class TestExtends { public static void main(String[] args) { SonClass s = new SonClass(66); } } class FooClass{ public FooClass() { System.out.println(100); } public FooClass(int count) { System.out.println(count); } } class SonClass extends FooClass{ public SonClass() { } public SonClass(int c) { System.out.println(1234); } }
Run result:
100
1234
Next, analyze why such a result is produced:
When the program executes the line SonClass s = new SonClass(66);
, it calls
public SonClass(int c) { System.out.println(1234); //在执行这行时系统会优先调用父类的无参构造函数super(); }
so the subclass When executing the above construction method, it is equivalent to executing the following code:
public SonClass(int c) { super(); // 必须在第一行调用,否则不能编译 System.out.println(1234); //在执行这行时系统会优先调用父类的无参构造函数super(); }
So the result is: 100 1234
Next, let’s introduce another In this case (explicit call), if the subclass constructor is written like this:
public SonClass(int c) { super(2); // 必须写在第一行,否则不能编译,显式调用父类构造函数后,系统就不在默认调用无参构造函数了 System.out.println(1234); }
The execution structure is:2 1234
Summary :
The constructor cannot be inherited and is only used to call in subclasses. (If the parent class does not have a parameterless constructor, it must be used when creating a subclass. Explicitly call the parameterized constructor of the parent class in the first line of the subclass constructor code body, otherwise it cannot be compiled);
If the parent class does not have a parameterized constructor, then in When creating a subclass, you do not need to explicitly call the parent class constructor. The system will call the parent class's no-argument constructor by default
super()
;If the parent class If there is no parameterless constructor, the system cannot adjust the default parameterless constructor, so the compilation cannot pass without displaying the call;
Additional explanation :
In java, after creating a parameterized constructor, the system no longer has a default parameterless constructor
If If there is no constructor in the parent class, the system will have a parameterless constructor by default
The above is the detailed content of Java inheritance, whether the subclass inherits the constructor of the parent class. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

In PHPOOP, self:: refers to the current class, parent:: refers to the parent class, static:: is used for late static binding. 1.self:: is used for static method and constant calls, but does not support late static binding. 2.parent:: is used for subclasses to call parent class methods, and private methods cannot be accessed. 3.static:: supports late static binding, suitable for inheritance and polymorphism, but may affect the readability of the code.

PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.

PHP is suitable for web development, especially in rapid development and processing dynamic content, but is not good at data science and enterprise-level applications. Compared with Python, PHP has more advantages in web development, but is not as good as Python in the field of data science; compared with Java, PHP performs worse in enterprise-level applications, but is more flexible in web development; compared with JavaScript, PHP is more concise in back-end development, but is not as good as JavaScript in front-end development.

PHP and Python each have their own advantages and are suitable for different scenarios. 1.PHP is suitable for web development and provides built-in web servers and rich function libraries. 2. Python is suitable for data science and machine learning, with concise syntax and a powerful standard library. When choosing, it should be decided based on project requirements.

Capsules are three-dimensional geometric figures, composed of a cylinder and a hemisphere at both ends. The volume of the capsule can be calculated by adding the volume of the cylinder and the volume of the hemisphere at both ends. This tutorial will discuss how to calculate the volume of a given capsule in Java using different methods. Capsule volume formula The formula for capsule volume is as follows: Capsule volume = Cylindrical volume Volume Two hemisphere volume in, r: The radius of the hemisphere. h: The height of the cylinder (excluding the hemisphere). Example 1 enter Radius = 5 units Height = 10 units Output Volume = 1570.8 cubic units explain Calculate volume using formula: Volume = π × r2 × h (4

The reasons why PHP is the preferred technology stack for many websites include its ease of use, strong community support, and widespread use. 1) Easy to learn and use, suitable for beginners. 2) Have a huge developer community and rich resources. 3) Widely used in WordPress, Drupal and other platforms. 4) Integrate tightly with web servers to simplify development deployment.
