什么是`public static <T> void main（String [] args）`代表什么？

Question

What does public static <X> void main(String[] args) stand for? I tried to understand but didn't get. I know about public static void main(String[] arg) . Thanks in advance.

Answer 1

Let's look at each bit in turn:

• public - it's a public method, accessible to anything which has access to the class in which this is declared
• <X> - this is (somewhat bizarrely) a generic method with an unbound type variable X
• static - the method is related to the type in which it's declared, not any specific instance of the type
• void - the method doesn't return a value
• main - the name of the method
• String[] args - a single parameter, of type String[] and called args

main is the entry point used by the JVM. When you run:

java foo.bar.Baz

it will try to find a main method in class foo.bar.Baz . I've never seen a generic main method before, admittedly. For more about generics in Java, read the Java Generics FAQ .

Answer 2

1. <X> is known as Type Parameter .

2. This is applicable to the methods, classes, variables, etc.. But its most important use is to make the Collections more type safe.

3. <X> will mark a certain Type within the main() method.

4. The whole sentence dissection is as follows:

   • public - is the access-modifier, means that this method is accessible from anywhere.
   • <X> - Type Parameter, as mentioned above
   • void - This method will not return anything
   • main - Method's name, main() method is the entry point of any pgm in java.
   • String[] : Array Of String.
   • args : Array reference variabl of type String.