Problem in Arrays passing.

[Himanshu Gupta]

public class FakeEventsGenerator {

	public static void main(String[] args) {
		/*Grid grid = new Grid(4);
		grid.initializeGrid(2, 2, DifficultLevel.BEGINNER);*/
		//grid.exploreLocation(1,0 );
		int[] arr = null;
		System.out.println(arr);
		initArray(arr);
		System.out.println(arr);
	}
	
	
	static void  initArray(int [] arr){
		arr =new int[]{1,2,3,4};
		System.out.println(arr);
	}
}

Output:

null
[I@1242719c
null

I am not able to understand that why the array is null here??

[Stephan van Hulst]

Java passes all arguments by value.

This means that the arr variable in your initArray method will refer to the same array that you pass to it in your main method, but it is a different variable from the arr variable in your main method.
You essentially pass the value null to it, then you assign a new array to arr in initArray, which is a different variable from arr in your main method, so nothing happens to your main method variable.

Instead, you could do something like this:

  ...
  int[] arr = initArray();
  ...

static int[] initArray() {
  return new int[] {1, 2, 3, 4};
}

[Himanshu Gupta]

What I wanted to do is to pass the null reference as an argument and let the other function assign a new array which will be used by the calling function.

As Java is pass by reference I was thinking that the reference is being passed and the same reference is used to assign a new Object if int array.

[Stephan van Hulst]

Himanshu Gupta wrote:As Java is pass by reference I was thinking that the reference is being passed and the same reference is used to assign a new Object if int array.

No, Java uses pass by value in all cases.

[Rob Spoor]

http://www.coderanch.com/how-to/java/CallByReferenceVsCallByValue

[VennkataReddy Kv]

plese go through attached file

[Matthew Brown]

Why is that relevant? I'm not sure of the point you're trying to make.

Remember Java passes references by value.

[Campbell Ritchie]

Agree it is by no means clear what you meant by that diagram. But I think you are mistaken there, if you think you can replace the null from a method call.