How to implement polymorphism in java
Overview of Java polymorphism: (Recommended: java video tutorial)
Polymorphism is an important feature of object-oriented programming languages, which allows basic The pointer or reference of the class points to the object of the derived class, and the dynamic binding of the method is implemented during specific access. Java The implementation of dynamic binding of method calls mainly relies on the method table, but the implementation through class reference calls (invokevitual) and interface reference calls (invokeinterface) is different.
Three conditions are required to implement polymorphism in java:
1. There needs to be an inheritance relationship.
2. There needs to be method rewriting.
3. There needs to be a reference from the parent class pointing to the subclass object.
The general process of class reference calling is: the Java compiler compiles the Java source code into a class file. During the compilation process, the called symbol reference is written into the class file according to the static type.
During execution, the JVM finds the symbolic reference of the calling method according to the class file, then finds the offset in the static type method table, and then determines the actual type of the object based on this pointer, using the actual type method table , the offset is the same as the offset of the method table in the static type. If the method is found in the method table of the actual type, it is called directly. Otherwise, it is considered that the method of the parent class has not been overridden. Search from bottom to top according to inheritance relationship.
As can be seen from the above figure, when the program is running and a certain class is required, the class loading subsystem will load the corresponding class file into the JVM. And internally establish the type information of the class (this type information is actually a data structure stored in the JVM by the class file), including all the information defined by the java class, including method code, class variables, member variables, and the content of this blog post. Key discussion methods table. This type information is stored in the method area.
Note that the type information in this method area is different from the class object stored in the heap. In the method area, the type information of this class has only a unique instance (so it is a memory area shared by each thread), and there can be multiple objects of this class in the heap. The type information in the method area can be accessed through the class object in the heap. Just like the Java reflection mechanism, all information of the class can be accessed through the class object.
For more java knowledge, please pay attention to the java basic tutorial column.
The above is the detailed content of How to implement polymorphism in java. 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

In this article, we have kept the most asked Java Spring Interview Questions with their detailed answers. So that you can crack the interview.

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

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.

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

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.

Java is a popular programming language that can be learned by both beginners and experienced developers. This tutorial starts with basic concepts and progresses through advanced topics. After installing the Java Development Kit, you can practice programming by creating a simple "Hello, World!" program. After you understand the code, use the command prompt to compile and run the program, and "Hello, World!" will be output on the console. Learning Java starts your programming journey, and as your mastery deepens, you can create more complex applications.
