##Override of java ? ? ? ? ? ? (Recommended learning: java course ? )
Rewriting is when a subclass rewrites the implementation process of a method that allows access to the parent class. Neither the return value nor the formal parameters can be changed. That is, the shell remains unchanged and the core is rewritten!
The advantage of overriding is that subclasses can define their own behavior as needed. In other words, subclasses can implement the methods of the parent class as needed. Overriding methods cannot throw new checked exceptions or exceptions that are broader than the overridden method declaration.For example:
A method of the parent class declares a checked exception IOException, but when overriding this method, you cannot throw Exception because Exception is IOException The parent class of IOException can only throw exceptions of subclasses of IOException. In object-oriented principles, overriding means that any existing method can be overridden.The examples are as follows:
class Animal{
public void move(){
System.out.println("動(dòng)物可以移動(dòng)"); }}
class Dog extends Animal{
public void move(){
System.out.println("狗可以跑和走"); }}
public class TestDog{
public static void main(String args[]){
Animal a = new Animal(); // Animal 對(duì)象
Animal b = new Dog(); // Dog 對(duì)象
a.move();// 執(zhí)行 Animal 類的方法
b.move();//執(zhí)行 Dog 類的方法
}}The compilation and running results of the above examples are as follows:
動(dòng)物可以移動(dòng) 狗可以跑和走As you can see in the above example, although b belongs to Animal type , but it runs the move method of the Dog class. This is because during the compilation phase, only the reference type of the parameter is checked. However, at runtime, the Java Virtual Machine (JVM) specifies the type of object and runs the object's methods.
The above is the detailed content of what is java rewriting. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
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)
VSCode settings.json location
Aug 01, 2025 am 06:12 AM
The settings.json file is located in the user-level or workspace-level path and is used to customize VSCode settings. 1. User-level path: Windows is C:\Users\\AppData\Roaming\Code\User\settings.json, macOS is /Users//Library/ApplicationSupport/Code/User/settings.json, Linux is /home//.config/Code/User/settings.json; 2. Workspace-level path: .vscode/settings in the project root directory
How to handle transactions in Java with JDBC?
Aug 02, 2025 pm 12:29 PM
To correctly handle JDBC transactions, you must first turn off the automatic commit mode, then perform multiple operations, and finally commit or rollback according to the results; 1. Call conn.setAutoCommit(false) to start the transaction; 2. Execute multiple SQL operations, such as INSERT and UPDATE; 3. Call conn.commit() if all operations are successful, and call conn.rollback() if an exception occurs to ensure data consistency; at the same time, try-with-resources should be used to manage resources, properly handle exceptions and close connections to avoid connection leakage; in addition, it is recommended to use connection pools and set save points to achieve partial rollback, and keep transactions as short as possible to improve performance.
Mastering Dependency Injection in Java with Spring and Guice
Aug 01, 2025 am 05:53 AM
DependencyInjection(DI)isadesignpatternwhereobjectsreceivedependenciesexternally,promotingloosecouplingandeasiertestingthroughconstructor,setter,orfieldinjection.2.SpringFrameworkusesannotationslike@Component,@Service,and@AutowiredwithJava-basedconfi
Understanding the Java Virtual Machine (JVM) Internals
Aug 01, 2025 am 06:31 AM
TheJVMenablesJava’s"writeonce,runanywhere"capabilitybyexecutingbytecodethroughfourmaincomponents:1.TheClassLoaderSubsystemloads,links,andinitializes.classfilesusingbootstrap,extension,andapplicationclassloaders,ensuringsecureandlazyclassloa
How to work with Calendar in Java?
Aug 02, 2025 am 02:38 AM
Use classes in the java.time package to replace the old Date and Calendar classes; 2. Get the current date and time through LocalDate, LocalDateTime and LocalTime; 3. Create a specific date and time using the of() method; 4. Use the plus/minus method to immutably increase and decrease the time; 5. Use ZonedDateTime and ZoneId to process the time zone; 6. Format and parse date strings through DateTimeFormatter; 7. Use Instant to be compatible with the old date types when necessary; date processing in modern Java should give priority to using java.timeAPI, which provides clear, immutable and linear
Google Chrome cannot open local files
Aug 01, 2025 am 05:24 AM
ChromecanopenlocalfileslikeHTMLandPDFsbyusing"Openfile"ordraggingthemintothebrowser;ensuretheaddressstartswithfile:///;2.SecurityrestrictionsblockAJAX,localStorage,andcross-folderaccessonfile://;usealocalserverlikepython-mhttp.server8000tor
Understanding Network Ports and Firewalls
Aug 01, 2025 am 06:40 AM
Networkportsandfirewallsworktogethertoenablecommunicationwhileensuringsecurity.1.Networkportsarevirtualendpointsnumbered0–65535,withwell-knownportslike80(HTTP),443(HTTPS),22(SSH),and25(SMTP)identifyingspecificservices.2.PortsoperateoverTCP(reliable,c
Comparing Java Frameworks: Spring Boot vs Quarkus vs Micronaut
Aug 04, 2025 pm 12:48 PM
Pre-formanceTartuptimeMoryusage, Quarkusandmicronautleadduetocompile-Timeprocessingandgraalvsupport, Withquarkusoftenperforminglightbetterine ServerLess scenarios.2.Thyvelopecosyste,
