Difference between Integer and int?

read this:
http://mindprod.com/jgloss/intvsinteger.html

in short:
int is a primitive
Integer is a object

And you can work with collections and databases based on Integer objects, never with int.
Thus, you can put numbers into lists, trees and maps by encapsulating them as Integer.

;JOOP!

>>What's the difference between Integer and int? Performance or anything?
int --> primitive, mutable, high performance
Integer --> object, immutable,


>>Also, I'd like to be able to pass an integer value by reference, something like:
Java doesn't pass method arguments by reference; it passes them by value.

so to change the value of integer object in a methot you need to create a new one and return it;

      void Trial() {
          Integer n = new Integer(0);
          System.out.println(n.intValue());
          n = ChangeInt();
          System.out.println(n.intValue());
      }

      Integer ChangeInt()
      {
          return new Integer(5);
      }


for more info;
http://www.javaworld.com/javaworld/javaqa/2000-05/03-qa-0526-pass.html

>>Java doesn't pass method arguments by reference; it passes them by value.

I think its opposite..

Integer object is immutable, meaning by you cannot change the value, once integer object is constructed.

Similar to String object

Java always passes arguments by value. cf:
http://java.sun.com/developer/JDCTechTips/2001/tt1009.html

and of course this known one:
http://www.javaworld.com/javaworld/javaqa/2000-05/03-qa-0526-pass.html

>>I think its opposite.
have a look at the link i posted above.

dupe post, me and ysnky - link is pale. ;)

I don't understand though  - why did they design the language so that you can't pass an integer by reference. I mean what if you have a large number of variables to modify in a single method call:

void whatever(x, y, z)
{
}

and you want 'whatever()' to modify x,y,z - then you're in trouble, I guess you have to make some subclass to just encapsulate those three? Doesn't make sense to me, coming from C++ anyway. What is the logic behind the decision?

Thanks

Because int is one of 8 primitive data types, built into the language as reserved keywords. All languages must have primitives otherwise they would never be able to compile values and pass them through as recognisable values to the operating system and CPU. Objects are just fancy wrappers for primitives.

> why did they design the language so that you can't pass an integer by reference.

to reduce the possibility of side effects.
You end up with cleaner and more maintainable code without it (pass by ref) as there is no chance of your vars values getting changed without u knowing about it.

If you relly need it you could use a mutable integer class

Thnx, k.

for me, at least the point must be splited.
:-(