Problem with an array of objects

[emerald000]

First, the code to its bare-bones:

public class FooMain {

	public static void main(String[] args) {
		
		Foo[] bar = new Foo[3];
		
		System.out.println(bar[0].x); //Error thrown here
	
	}
}

public class Foo {

	public int x;
	
	public Foo() {
	
		x = 12;
		
    }
	
}

What I want to do is to create an array where each element of the array is a Foo object. By calling bar[0], I get the reference to the first Foo object, .... The code above compiles without a problem, but I get a null pointer exception on the line indicated above.

I really don't know what the problem is. If I create a single Foo (not in an array), it works correctly. If I create an array of int, it works too. But an array of Foo just won't work.

Thanks in advance for your help.

[Fubarable]

Object arrays are collections of variables, not objects, and they have to be filled with objects to work. One way to think of arrays is as if you were creating a parking lot. Starting out it has no cars, and you have to fill it with cars for each space to have any "meaning".

[yellowledbet]

You have to initialize objects shown below

First, the code to its bare-bones:

public class FooMain {

	public static void main(String[] args) {
		
		Foo[] bar = new Foo[3];

		////////////////////

                for(Foo f : bar){
                     f = new Foo();
                }
                /////////////////////
		System.out.println(bar[0].x); //Error thrown here
	
	}
}

public class Foo {

	public int x;
	
	public Foo() {
	
		x = 12;
		
    }
	
}

What I want to do is to create an array where each element of the array is a Foo object. By calling bar[0], I get the reference to the first Foo object, .... The code above compiles without a problem, but I get a null pointer exception on the line indicated above.

I really don't know what the problem is. If I create a single Foo (not in an array), it works correctly. If I create an array of int, it works too. But an array of Foo just won't work.

Thanks in advance for your help.

[Fubarable]

You have to initialize objects shown below

That won't work as you can't initialize items in an array using a for-each loop. Test it yourself and you'll see. You need to use a for loop.

e.g.

      // for (Foo f : bar) {
      // f = new Foo();
      // }

      for (int i = 0; i < bar.length; i++) {
         bar[i] = new Foo();
      }

[emerald000]

I thought the objects where getting initialized by calling the array. Is there a pretty way to do so, or only like this:

		for(int i=0;i<bar.length;i++) {
			bar[i] = new Foo();
		}

EDIT: I guess Fubarable pretty much answered a second before I posted.

[Fubarable]

Only the array is initialized by your first code, not the items in the array. You can initialize it in other ways if desired:

Foo[] bar = {new Foo(), new Foo(), new Foo(), new Foo(), new Foo(), new Foo(), new Foo(), new Foo()};

[yellowledbet]

my apologies. Too much C# lateley