Java generics mainly include "define generic classes", "define generic interfaces", "define generic methods", "instantiate generic classes or interfaces", "use wildcards" and "use generics". Six uses of "type qualification": 1. Define a generic class and use
to represent type parameters; 2. Define a generic interface and use to represent type parameters; 3. Define a generic method , use to represent type parameters; 4. When instantiating a generic class or interface, specify specific type parameters; 5. Use wildcards to represent a subtype or supertype of a certain generic type.
Java generics are mainly used in the following ways:
- Define generic classes
You can define a generic class, use
public?class?MyList<T>?{
????private?T[]?array;
????public?MyList(T[]?array)?{
????????this.array?=?array;
????}
????public?T?get(int?index)?{
????????return?array[index];
????}
}
- Define a generic interface
You can define a generic interface, use
public?interface?MyInterface<T>?{
????T?doSomething();
}
- Define a generic method
You can define a generic method, use
public?<T>?T?doSomething(T?param)?{
????//?...
}
- Instantiate a generic class or interface
When instantiating a generic class or interface, specific type parameters must be specified, for example:
MyList<String>?list?=?new?MyList<>(new?String[]{"a",?"b",?"c"});
- Use wildcards
You can use wildcards to represent subtypes or supertypes of a certain generic type, including ?, ? extends T and ? super T. , for example:
MyList<? extends Number>?list1?=?new?MyList<>(new?Integer[]{1,?2,?3});
MyList<? super Integer>?list2?=?new?MyList<>(new?Number[]{1.0,?2.0,?3.0});
Among them, list1 can accept any type that is a subtype of Number (such as Integer, Float, etc.) as an element, while list2 can accept any type that is a supertype of Integer (such as Number, Object, etc.) as elements.
- Using generic qualification
You can use generic qualification to limit the scope of type parameters, including extends and super, for example:
public?<T extends Number>?void?doSomething(T?param)?{
????//?...
}
Among them,
The above is the detailed content of How to use Java generics. 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)
Hot Topics
Selecting Specific Columns | Performance Optimization
Jun 27, 2025 pm 05:46 PM
Selectingonlyneededcolumnsimprovesperformancebyreducingresourceusage.1.Fetchingallcolumnsincreasesmemory,network,andprocessingoverhead.2.Unnecessarydataretrievalpreventseffectiveindexuse,raisesdiskI/O,andslowsqueryexecution.3.Tooptimize,identifyrequi
What is the `enum` type in Java?
Jul 02, 2025 am 01:31 AM
Enums in Java are special classes that represent fixed number of constant values. 1. Use the enum keyword definition; 2. Each enum value is a public static final instance of the enum type; 3. It can include fields, constructors and methods to add behavior to each constant; 4. It can be used in switch statements, supports direct comparison, and provides built-in methods such as name(), ordinal(), values() and valueOf(); 5. Enumeration can improve the type safety, readability and flexibility of the code, and is suitable for limited collection scenarios such as status codes, colors or week.
Applying Semantic Structure with article, section, and aside in HTML
Jul 05, 2025 am 02:03 AM
The rational use of semantic tags in HTML can improve page structure clarity, accessibility and SEO effects. 1. Used for independent content blocks, such as blog posts or comments, it must be self-contained; 2. Used for classification related content, usually including titles, and is suitable for different modules of the page; 3. Used for auxiliary information related to the main content but not core, such as sidebar recommendations or author profiles. In actual development, labels should be combined and other, avoid excessive nesting, keep the structure simple, and verify the rationality of the structure through developer tools.
VSCode debugger for Java setup guide
Jul 01, 2025 am 12:22 AM
The key steps in configuring the Java debugging environment on VSCode include: 1. Install JDK and verify; 2. Install JavaExtensionPack and DebuggerforJava plug-in; 3. Create and configure the launch.json file, specify mainClass and projectName; 4. Set up the correct project structure to ensure the source code path and compilation output are correct; 5. Use debugging techniques such as Watch, F8/F10/F11 shortcut keys and methods to deal with common problems such as class not found or JVM attachment failure.
How do I set up VS Code for Java development?
Jun 29, 2025 am 12:23 AM
To use VSCode for Java development, you need to install the necessary extensions, configure the JDK and set up the workspace. 1. Install JavaExtensionPack, including language support, debugging integration, build tools and code completion functions; optional JavaTestRunner or SpringBoot extension package. 2. Install at least JDK17 and verify through java-version and javac-version; set the JAVA_HOME environment variable, or switch multiple JDKs in the status bar at the bottom of VSCode. 3. After opening the project folder, make sure the project structure is correct and enable automatic saving, adjust the formatting rules, enable code checking, and configure the compilation task to optimize the opening.
Windows search bar not typing
Jul 02, 2025 am 10:55 AM
When the Windows search bar cannot enter text, common solutions are: 1. Restart the Explorer or computer, open the Task Manager to restart the "Windows Explorer" process, or restart the device directly; 2. Switch or uninstall the input method, try to use the English input method or Microsoft's own input method to eliminate third-party input method conflicts; 3. Run the system file check tool, execute the sfc/scannow command in the command prompt to repair the system files; 4. Reset or rebuild the search index, and rebuild it through the "Index Options" in the "Control Panel". Usually, we start with simple steps first, and most problems can be solved step by step.
Differences Between Callable and Runnable in Java
Jul 04, 2025 am 02:50 AM
There are three main differences between Callable and Runnable in Java. First, the callable method can return the result, suitable for tasks that need to return values, such as Callable; while the run() method of Runnable has no return value, suitable for tasks that do not need to return, such as logging. Second, Callable allows to throw checked exceptions to facilitate error transmission; while Runnable must handle exceptions internally. Third, Runnable can be directly passed to Thread or ExecutorService, while Callable can only be submitted to ExecutorService and returns the Future object to
Why use the `Serializable` interface?
Jun 26, 2025 am 01:02 AM
ImplementingtheSerializableinterfaceinJavaallowsaclasstobeconvertedintoabytestreamforstorageortransmission.Asamarkerinterfacewithnomethods,itsignalsthattheclassisreadyforserialization,enablingmechanismslikeObjectOutputStreamtoprocessit.Failingtoimple
