Please explain to me this basics in java !! array delaration

[javanew]

public class Driver {
	 
	    int[] a;
	    int lastItem;
	 
	public static void main(String []args){
	

		a[0] = 4; // THIS DOES NOT WORK ?? WHY ?? PLEASE EXPLAIN:confused:....
		
		
	
		for(int s = 0 ; s < a.length; s++){
		System.out.println(" "+a[s] );}
		
		
		
	}
	
}

[Fubarable]

Your problems are several-fold. For one, the variable a is declared:

int[] a;

but never initialized

a = new int[5];

For another, a has been declared as a non-static class field, but you're trying to access it from within a static method, and it simply doesn't exist by itself within a static method. It only exists in association with the context of a Driver object.

[Eranga]

@OP, please use code tags when you are posting again.

[Eranga]

Go through the comments I've added in the following code.

public class Driver {
	 
       int[] a;
       // A variable is declared. [] stands for the declaration of an array. But not initialize. That means in an array you've to define how many items you want to store in advance, before use.

       int lastItem;

	 
       public static void main(String []args){
       a[0] = 4; // THIS DOES NOT WORK ?? WHY ?? PLEASE EXPLAIN:confused:....

       // In above line you found an error because the first element, a[0] is the first element of an array(items are zero based indexing), could not found by your compiler. Because compiler dosen't know how many items there have actually, in simple word.
		
       for(int s = 0 ; s < a.length; s++){
              System.out.println(" "+a[s] );}
	}
}

If you are confusing with my comments let me know.