what <T> signifies in <T> void say() [duplicate]

Question

What <T> signifies in following code snippet?

class Test {    
     <T> void say() {

     }    
}

Answer 1

In your example it really does not make sense. But in other cases, if method's return type is void <T> still can be used as expected generic parameters type. Consider this

public static <T> void test(List<T> list1, List<T> list2) {
    list1.addAll(list2);
}

public static void main(String[] args) throws Exception {
    test(Arrays.asList(1, 1), Arrays.asList("1", "1"));
}

type safety control, javac gives an error, test() expects Lists of the same type.

Another example java.util.Collections.fill

public static <T> void fill(List<? super T> list, T obj) {
    ....
}    

type safety control again.

Answer 2

It introduces a type placeholder, where T maybe pretty much any type. This is typically useful if T is part of the signature (either as a parameter or a return type):

<T> void say(T myT) {}
say<Object>(myObject);
say<String>(myString);

<U> U foo(U u) { return u; }
String s = foo<String>("");

It's rarely useful to introduce a type parameter just for internal use, as the actual T is often more interesting for the consumer than the method.

Answer 3

See this doc about generics in java

But it is useful only if you have parametized types in the argument list.