does return return the actual object or a copy of the object?

Newbie & Debugging Questions
#1

the post name basically says it , im using a function when I require to return a specific object from a list so that I can modify .

private Object myobject;
	public void bind(Object obj){
		myobject = obj;
	}
	public Object obtain(){
		return myobject;//when this is returned is it myobject ie a c++ reference style object or a copy
	}
#2

The short answer is that no, it’s not a copy. What happened when you wrote a little example program to test this out?

#3

In the same manner Java’s methods receive arguments by value, it also returns 1 as value.
Keyword return sends following evaluated expression back to its callee. ::slight_smile:
For example in return myobject; it evaluates myobject instance variable, which results in the reference value stored in it.
So it’s the reference value stored in myobject which ends up being returned in that statement. :wink:

#4

For more info on what GoToLoop is saying, I recommend you read this: http://www.javaranch.com/campfire/StoryCups.jsp

And then read this: http://www.javaranch.com/campfire/StoryPassBy.jsp

#5

Ugh , by reference I literally mean the c++ & reference where you are able to create int &a = b; editing a would modify b. When I ran the little bit of code on this it didnt edit the original , I Want to know is there anyway that I can edit the original variable with another variable in the same way that c++ does it or should I just build setting methods.

#6

Excellent articles KevinWorkman! Now I don’t have to explain this confusing but important concept by myself anymore! ;D
However I’ve found out some glitches on 'em: :-X

[quote](-2 to the 7th) through (2 to the 7th) -1. Why that little -1 on the end? Because zero is in there, and zero counts as negative.
[/quote]
Value 0 counts as positive in computation. After all, its sign bit is 0 too! ::slight_smile:

[quote]boolean - … you’re not supposed to ask. It holds a value of true or false, but it’s really stored as a numeric value, probably in a byte-sized cup.
[/quote]
AFAIK, in Oracle, OpenJDK, Dalvik Java implementations, boolean primitive type is a whole 8-bit byte. 7 bits go to waste! :’(

[quote]… remember that the object is created out on the garbage-collectible heap. Always.
[/quote]
That’s gonna surprise many Java veterans but, since Java 6, it features an über feature called “Escape Analysis”:

Java can decide to allocate a whole object in the stack instead of regular heap if it’s sure its reference won’t escape/survive its local scope boundary! :point:

#7

Java creators, by purpose, have left any explicit address & indirection operators outta it! :o
We’ve only got the member reference operator, which is a simple dot!
And therefore, we can’t use a variable/field to directly change the value stored in another variable/field, ever! :-X

#8

So if you want to have lots of booleans but not waste memory, use a BitSet.

[quote]if it’s sure its reference won’t escape/survive its local scope boundary!
[/quote]
Note that this is more involved than one might expect, and in my experience happens infrequently.

Note that you can store fields in some kind of Reference type (even something as simple as a 1-element array) to (crudely) simulate this functionality.
The provided atomic impl is actually pretty useful at times: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/atomic/AtomicReference.html

#9

Most modern compilers align data. Therefore, plain C never really stores a boolean on a single bit, come down to Earth.