Reference of an object

[saiganesh44]

Can anyone explain, why the output is that way? I mean, if the argument is just a reference of the object which is passed, why isn't the 'i' value changed ? which did in case of 'k' value

public static void change(int j) {
		j = 20;
	}

	public static void change(info in){
		in.setK(20);
	}
	
	public class info {
		int k;

		public void setK(int k) {
			this.k = k;
		}

		public int getK() {
			return k;
		}
	}

	public static void main(String args[]) {
		int i = 10;
		System.out.println("initial value of i is " + i);
		change(i);
		System.out.println("after value of i " + i);
		info infObj = new ObjectReference().new info();
		infObj.setK(i);
		System.out.println("initial " + infObj.getK());
		change(infObj);
		System.out.println("after " + infObj.getK());
	}

OUTPUT :
initial value of i is 10
after value of i 10
initial 10
after 20

[jlczuk]

I'm going to give you a horribly vague answer because I don't know 'proper' terminology to use. In your usage, the parameter you are passing is not really a reference because primitive types like int are not objects. Therefore, you cannot change the value of 'i" as seen by main() by passing it as a parameter to change().

[jlczuk]

This should help you understand better. Scroll down to the "Passing Primitive Data Type Arguments" section of the Passing Information to a Method or a Constructor topic of the Classes and Objects Tutorial.

[kosmos890]

It is necessary to use ObjectReference() constructor ?

[jlczuk]

It is necessary to use ObjectReference() constructor ?

Please don't hijack the thread. Start a new one or even do a search, I'm sure there are a hundred variations of that basic question. Search on "constructor".

[saiganesh44]

This should help you understand better. Scroll down to the "Passing Primitive Data Type Arguments" section of the Passing Information to a Method or a Constructor topic of the Classes and Objects Tutorial.

hmmmmmmm, now it get the difference between primitive data type and reference data type, it is confusing though. Thanx

[DarrylBurke]

You can find a very clear (and entertaining!) article here: JavaRanch Campfire - Cup Size: a Story About Variables

After you've read and digested it, go on to part two linked from the end of part one.

db

[saiganesh44]

You can find a very clear (and entertaining!) article here: JavaRanch Campfire - Cup Size: a Story About Variables

After you've read and digested it, go on to part two linked from the end of part one.

That part two link best explained my question, Thnx :)