java - generics collections.mixin raw and generic type. Integer -> String - exception but String -> Integer works good -

i confusing 2 code snippets:

snippet 1

    list list = new arraylist();     list.add("1");     iterator<integer> iterator = list.iterator();     system.out.println(iterator.next()); 

this code executes , outs 1 console

snippet 2

    list list = new arraylist();     list.add(1);     iterator<string> iterator = list.iterator();     system.out.println(iterator.next()); 

result of - runtimeexception

java.lang.classcastexception: java.lang.integer cannot cast java.lang.string 

i confusing because both these rows wrong:

    integer integer = "123";     string  string = 1; 

it compile error.

why generis behaviour different?

p.s.

i prepare scjp exam , don't mix raw type , generics;

printstream, class of system.out, has number of println overloads. in particular, has an overload takes object , an overload takes string.

in first example,

list list = new arraylist(); list.add("1"); iterator<integer> iterator = list.iterator(); system.out.println(iterator.next()); 

the compiler expects iterator.next() produce integer, , best match object version of println. compiler generates call object version of method, happens work fine string comes out of iterator.

in second example,

list list = new arraylist(); list.add(1); iterator<string> iterator = list.iterator(); system.out.println(iterator.next()); 

the compiler expects iterator.next() produce string, , best match string version of println. compiler generates call string version of method, , due type erasure (which makes runtime type of iterator.next() object), generates runtime cast object string. cast fails integer comes out of iterator, causing exception see.