Why use get/set instead of exposing properties

One 、 problem

Most fields are accessed through get/set Method to indirectly access , Why not set the field to public property directly public Well ？ The answer lies in the future possibility of the former .

Two 、 Maintain control over this attribute

adopt get/set Disclose it and use public The main difference between attributes is Maintain control over this attribute . If you expose a field , That means you can access it directly . then , The caller can do anything , Whether intentionally or unintentionally . for example , You can set the field to null , If you use this field in another method , Then this method may be caused by Null pointer exception And collapse .

however , If provided get/set, It can provide indirect access while fully controlling . The only way to set values is through set, The value is obtained by get , Fields have only one entry and one exit . because get/set Is a way to allow code blocks , So you can verify them , Object determines whether to set the caller value . This also applies to get Method —— You can decide to return the actual reference or clone it , And return it to the caller .

therefore ,get/set It acts as a fuse or circuit breaker . The current must pass through the fuse , If something goes wrong , The fuse is separated from the main circuit , The circuit is safe . Again , If anything goes wrong ,set This value will not be passed to the class member field .

Generally, I don't write anything in get/set In the method . Only return and set fields , Just like public fields . By writing get/set, Created a clause for adding any validation methods in the future , There is currently no validation , But if anything goes wrong in the future , It's just set Add validation logic .

3、 ... and 、 The code is generic

When a field has no such validation constraint , Why bother writing get/set？ The key to the problem is to avoid unnecessarily complicating the code . Developers are trying to make the code base more generic , Adapt to any change . Although most of the changes you think of will never come . therefore ,get/set Will not complicate the code , This will be verified in the code .