java. Comparison between lang. void and void and introduction to their usage

Void is not a function, but a modifier of a method. Void means that the method does not return a value, which means that the method will only run the statements in the method, but will not return anything.

java. Lang.void is a type. For example, assign null to a void reference.

As you can see from the code of the void class, the void type cannot be inherited or instantiated.

Void as the return result of the function means that the function returns null (no other types can be returned except null).

Before generics, void was generally used in reflection. For example, the following code prints the method name whose return type is void.

After generics appear, the void type will be used in some scenarios. For example, future < T > is used to save the results. The get method of future will return a result (type T).

But what if the operation does not return a value? In this case, it can be represented by future < void >. When the result is calculated after calling get, null will be returned. In addition, void is also used in valueless maps, such as map < T, void > so that the map will have the same function as set < T >.

Therefore, when you use generics, the function does not need to return a result or an object does not need a value, you can use Java Lang. void type representation.

reference resources:

java. lava. Comparison between void and void,

http://stackoverflow.com/questions/10839042/what-is-the-difference-between-java-lang-void-and-void

How to judge whether a function returns void,

http://stackoverflow.com/questions/1924253/how-to-determine-by-reflection-if-a-method-returns-void

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