java - Generics vs. Method Overloading -

i have 3 methods:

//1 -- check 1 item public static <t> void containsatleast(string message,                                        t expecteditem,                                        collection<? extends t> found) {     if (!found.contains(expecteditem))         assert.fail("...");         }  //2 -- check several items public static <t> void containsatleast(string message,                                        collection<? extends t> expecteditems,                                        collection<t> found) {     (t expteteditem : expecteditems)         containsatleast(message, expteteditem, found);         }  //3 -- check several items, without message parameter public static <t> void containsatleast(collection<? extends t> expecteditems,                                        collection<? extends t> found) {     containsatleast(null, expecteditems, found); } 

i expect method //3 invoke //2 not, invoke method //1. there mistake in expect?

*i use sdk 1.7.0_25 , eclipse 4.3*

your second method expects generic type of expecteditems (? extends t) subtype of generic type of found (t).

in third method, there no subtype relationship between 2 generic types. both extend t siblings example.

so second method can't called.

example: imagine call third method types:

containsatleast(collection<integer> e, collection<string> f) 

so t in third method object. , first method called t = object too.