Three Java built-in annotations

In Java, annotations (Annotations) were introduced in Java5 and are used to describe meta-information of Java code. Usually annotations do not directly affect the execution of the code, although some annotations can be used to affect the execution of the code. There are three built-in annotations in Java, which are used to provide instructions to the compiler. They are:

• @Deprecated Expired, the representation method is not recommended

• @Override Rewritten, the logo is overwritten Methods of its parent class

• @SuppressWarnings Suppress warnings, suppress warnings

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##Deprecated Annotations

You can modify classes, methods, and variables. Classes, methods, variables, etc. modified by @Deprecated in the java source code indicate classes, methods, etc. that are not recommended for use, may cause errors, and may be deleted in the future. If used now, programs that use these classes and methods in the future will have errors when updating new JDKs, jar packages, etc., and support will no longer be provided.

The classes, methods, and variables in personal programs are modified with @Deprecated to prevent yourself and others from using such methods and methods again in the future. When the compiler encounters classes, methods, and variables modified with @Deprecated during compilation, it will prompt corresponding warning messages.

Override annotation

Indicates that the annotated method needs to override the method in the super class. If a method uses this annotation, it does not override the method in the super class. method (such as wrong capitalization, wrong parameters, or a method defined by the subclass itself), the compiler will generate an error.

Overriding the methods of the parent class or interface in the subclass, @Overide is not necessary. However, it is still recommended to use this annotation. In some cases, if you change the name of a parent class method, the previously overridden subclass method will no longer be an override. Without @Overide, you will not notice it. methods of this subclass. With this annotation modification, the compiler will prompt you for this information.

Suppresswarnings Annotation

@SuppressWarnings is used to suppress the compiler from generating warning messages. The elements that can be modified are classes, methods, method parameters, attributes, and local variables. It can achieve the purpose of suppressing warnings generated by the compiler during compilation. Use the @SuppressWarnings annotation and adopt the proximity principle. For example, if a warning occurs in a method, try to use @SuppressWarnings to annotate this method instead of the class where the annotated method is located. The smaller the scope, the better, because a large scope is not conducive to discovering warning messages of other methods under this class.

However, it is highly discouraged to use the @SuppressWarnings annotation. Using this annotation, developers cannot see the corresponding warnings prompted by the compiler during compilation, and cannot choose better or newer classes and methods or write more standardized coding. At the same time, when the source code of JDK, jar package, etc. is updated later, the code annotated with @SuppressWarnings may be supported by the new JDK, jar package code, errors occur, and still need to be modified.

In Java, annotations (Annotations) were introduced in Java5 and are used to describe meta-information of Java code. Usually annotations will not directly affect the execution of the code, although some annotations can be used to affect the code. implement. There are three built-in annotations in Java, which are used to provide instructions to the compiler. They are:

• @Deprecated Expired, indicating that the method is not recommended for use

• @Override Rewritten, the identifier overrides its parent Class method

• @SuppressWarnings Suppress warnings, suppress warnings

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