Long vs Integer, long vs int, what to use and when?

Question

Sometimes I see API\'s using long or Long or int or Integer, and I can\'t figure how the decision is made for that?

Answer 1

a) object Class "Long" versus primitive type "long". (At least in Java)

b) There are different (even unclear) memory-sizes of the primitive types:

Java - all clear: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

• byte, char .. 1B .. 8b
• short int .. 2B .. 16b
• int .. .. .. .. 4B .. 32b
• long int .. 8B .. 64b

C .. just mess: https://en.wikipedia.org/wiki/C_data_types

• short .. .. 16b
• int .. .. .. 16b ... wtf?!?!
• long .. .. 32b
• long long .. 64b .. mess! :-/