Swapping of Object in Java

[pratik gaurav]

public class Swap {
	int x,y;
	public Swap(int x,int y) {            // constructor initialized
		this.x=x;
		this.y=y;
	}
	static void swap(Swap obj[])       //array of objects and static method is called
	{
		Swap temp;                     // swapping without the help of extra variable
		temp=obj[0];
		obj[0]=obj[1];
		obj[1]=temp;
	}
	public static void main(String[] args) {
		Swap obj[]=new Swap[2];  // array of objects
		obj[0]= new Swap(10,20); // initialization of obj
		obj[1]= new Swap(30,40);
		System.out.println(
                  "before swaping"+obj[0].x+" "+obj[0].y+" "+obj[1].x+" "+obj[1].y);
		swap(obj);                     // static method is called
		System.out.println(
                  "after swaping"+obj[0].x+" "+obj[0].y+" "+obj[1].x+" "+obj[1].y);
	}
}

[Kemal Sokolovic]

And the question is...?

[Campbell Ritchie]

Welcome to the Ranch
Code tags are supposed to work when you put [code=java] before your code and and [/code] after it. Also keep your lines short, as it says here. don’t worry, I have sorted it out for you and you can see how much better it looks
Also please tell us what the problem is. If we don’t know, we can’t help you. In this case, I think the compiler is telling you off and you never get near running the code at all.

Your swapping class won’t do what you expect. You have two fields, which you never use.
You have some poor style, too. apart from using tabs for indenting, you have put the [] for an array in the wrong place. Put the [] before the name of the parameter and then you can see the type correctly. Not Swap obj[]. Then you will be able to see the type that the compiler thinks you are trying to pass. It doesn’t matter what you think you are trying to pass, it is whether you can convince the compiler of it.

Don’t write a swap method which swaps elements 0 and 1. Write a swap method which takes two ints, remembering you will suffer an Exception if the numbers are inappropriate

/**
 * Alters the array by swapping its i-th and j-th members
 */
public static void swap(... array, int i, int j)
{
   if (i < 0 || j < 0 || i >= array.length || j >= array.length)
   {
      throw new ArrayIndexOutOfBoundsException("Using indices " + i +
         " and " + j + " in " + array.length + "-element array");
   }
   if ( i != j)
   {
      // You already know how to swap array elements
   }
}

[pratik gaurav]

Kemal Sokolovic wrote:And the question is...?

swapping to two object using call by refrence.

[Matthew Brown]

pratik gaurav wrote:swapping to two object using call by reference.

If that's a question, the answer is "no". Java doesn't have pass by reference. It passes references by value, which is a small but important difference.

[Winston Gutkowski]

pratik gaurav wrote:swapping to two object using call by refrence.

Let's back up.

What are you trying to do Pratik? And explain it to us in English, not in Java. What is your Swap class intended to accomplish?

Winston

[Campbell Ritchie]

If you mean swapping two elements in an array, that is something different. You are not given the two objects, but one different object—the array. You are not so much swapping as altering the state of the array. Which you can do in a method which is passed a mutable object.

[pratik gaurav]

i am trying to sawp the reference of two object.
i know i'm newbie.. but please look at it you will come to know what i am trying to explain

[Jeff Verdegan]

pratik gaurav wrote:i am trying to sawp the reference of two object.
i know i'm newbie.. but please look at it you will come to know what i am trying to explain

It's already been fully explained. Please re-read the previous replies carefully.

There is no pass-by-reference in Java. If you want to swap two references, they need to be elements of an array or members of a class.

What specific question do you still have?

[fred rosenberger]

pratik gaurav wrote:please look at it you will come to know what i am trying to explain

If you want to get the most from this site, you should probably read our FAQ on HowToAskQuestionsOnJavaRanch (<---that is a link - click it). But in brief, you want to make it as easy as possible for people to help you. Saying "read the code I posted" is lazy, and turns a lot of people off from helping you.

Instead, if you said "well, I'm trying to swap two objects in memory. I wrote the above code, but I think it doesn't work because....", folks will know they are answering you question instead of guessing what that question is.