为什么只能为静态方法定义泛型？

Question

Book, Introduction to Java Programming, says, "A generic type can be defined for a static method." Why instance methods can't be generic?

Answer 1

Instance methods be generic. The following code compiles with Java 5 and later. As you can see, I have defined a generic instance method and a generic static method in the same way.

package com.company;

public class Generics {
    public <T> T returnAGenericType(T returnThisOne) {
        return returnThisOne;
    }

    public static <T> T returnAGenericTypeStatic(T returnThisOne) {
        return returnThisOne;
    }
}

ArrayList::toArray , ArrayList::get and ArrayList::set are all examples of instance methods with generic type parameters.