Is generics bound part of method signature in Java?

Question

I realized today that this compiles and runs fine:

public class Test {
    public static <T> T handle(T val) {
        System.out.println("T");
        return val;
    }

    public static <T extends String> T handle(T val) {
        System.out.println("T extends String");
        return val;
    }
}

The two handle methods has the same name, and same number and type (?) of parameters. The only difference is that the second handle method has a stricter generic bound. IDE does not complain at all, and the code compiles fine. At run time method is selected as expected - e.g. Test.handle("this is a string") will call into the second method and Test.handle(10) will invoke the first one.

Is generics bound considered part of the method signature? or is it a method overload resolution magic?

Answer 1

Generics offer compile-time type-safety; At runtime, your methods erase to the following:

public static Object handle(Object val) {
    System.out.println("T");
    return val;
}

public static String handle(String val) {
    System.out.println("T extends String");
    return val;
}

Due to method overloading, handle(String) will be called when passing a String, and handle(Object) will be called when passing any other Object (keep in mind String is final and can have no children).