java - How Generics at Class Level Parameter works -

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• java generics type erasure of method parameters 3 answers

consider following code java puzzlers

class gloam<t>{  string glom(collection<?> objs ) {     system.out.println("collection");     string result = "";     (object o : objs ){         result += o;     }     return result; }  int glom(list <integer> ints ) {     system.out.println("list");     int result = 0;     ( int : ints )         result += ;     return result; }  public static void main(string[] args) {     list<string> strings = arrays.aslist("1", "2", "3");     system.out.println(new gloam().glom(strings)); }  } 

when run program gives class cast exception, if provide generic argument gloam class in main method works fine.

public static void main(string[] args) {     list<string> strings = arrays.aslist("1", "2", "3");     system.out.println(new gloam<date>().glom(strings)); } 

i don't understand how generic works in class type parameter ?

with no generic type passed constructor, types erased , compiler presented choices

string glom ( collection );  int glom ( list ); 

the type erased strings variable defined in main, type list.

because list more specific collection chooses int glom ( list ).

now, if have specified generic parameter, no type erasure happens, , compiler knows cannot match int glom ( list<integer> ) list<string>, falls string glom ( collection<?> )