What is the difference between an int and an Integer in Java and C#?

Question

I was reading More Joel on Software when I came across Joel Spolsky saying something about a particular type of programmer knowing the difference between an i

Answer 1

01. Integer can be null. But int cannot be null.

Integer value1 = null; //OK

int value2 = null      //Error

02. Only can pass Wrapper Classes type values to any collection class.

(Wrapper Classes - Boolean,Character,Byte,Short,Integer,Long,Float,Double)

List element = new ArrayList<>();
int valueInt = 10;
Integer  valueInteger = new Integer(value);
element.add(valueInteger);

But normally we add primitive values to collection class? Is point 02 correct?

List element = new ArrayList<>();
element.add(5);

Yes 02 is correct, beacouse autoboxing.

Autoboxing is the automatic conversion that the java compiler makes between the primitive type and their corresponding wrapper class.

Then 5 convert as Integer value by autoboxing.