Common annotations and function introduction in Java class libraries

Common annotations and function introduction in Java class libraries Note is a special grammar element in the Java language, which can be used to add additional metadata information to code elements such as class, methods, variables.Through annotations, we can embed some specific configurations in the code, so that the code can be configured, controlled, and expanded without changing the source code.In the Java class library, there are some commonly used annotations that play an important role in various fields.Here are some commonly used annotations and functions. 1. @Override: It is used to represent a method rewriting the method of the parent class.It reminds the compiler for a static inspection to ensure that the method of rewriting is effective.For example: public class Animal { public void eat() { System.out.println("Animal eating..."); } } public class Dog extends Animal { @Override public void eat() { System.out.println("Dog eating..."); } } 2. @Deprecated: It is not recommended to indicate that a method, class or interface is outdated, and it is not recommended.The compiler will warn when using these outdated elements.For example: @Deprecated public class OldClass { // ... } 3. @SuppressWarnings: It is used to inhibit the warning generated by the compiler.It can be used to ignore some unrelated or correct but confusing warnings.For example: @SuppressWarnings("unchecked") public List<String> getList() { return new ArrayList(); } 4. @functionalInterface: Used to mark a interface as a function interface, that is, only one abstract method.This annotation can ensure that the interface meets the requirements of Lambda expression.For example: @FunctionalInterface public interface MyFunction { void doSomething(); } 5. @SuppressWarnings: It is thread -safe for declaration of a way to declare a method.This annotation can be provided for tools, frameworks, etc. to check and confirm.For example: @ThreadSafe public class MyClass { // ... } 6. @entity: Used to declare that a class is a persistent object.This annotation is usually used with the ORM (object relationship mapping) framework to describe the mapping relationship between the object and the database table.For example: @Entity public class User { // ... } The above is some commonly used annotations and function introduction in the Java class library.These annotations can make our code more easy to read and maintain, and can be further processed by tools or frameworks.Therefore, reasonable use of annotations can improve the development efficiency and quality of code.