Why is implicit conversion from int to Long not possible?

Question

I can implicitly conver int to long and long to Long. Why is it not possible to implicitly convert int to Long? Why can't Java do the implicit conversion on the last line of the example?

int i = 10; //OK
long primitiveLong = i;  //OK
Long boxedLong = primitiveLong;  //OK
boxedLong = i; //Type mismatch: cannot convert from int to Long

Answer 1

Long and Integer are objects. Boxing/unboxing only works with primitives. Doing Long boxedLong = i is like Long boxedLong = new Integer(10), that's a no no ! Plus, remember that there is no inheritance between Long and Integer so even Integer i = new Long() is not valid

Answer 2

Boxing only works with primitives. That's why.

Try this: Long.valueOf(int);

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