Two Dimensional Arrays in Java Lang

Question

My question is,can i check a place if null,or set a place to null in two dimensional String array with my way.

String [][] xx=new String [][]
public void set(int a,int b)
  {
 xx[a][b]=null;//setting null
 }
 .
 .
 .
 .
 .
 if(xx[a][b]==null)//check if null
  ///some codes

İs it possible?Or if wrong,how to do it.?Regards..

Did you try it and it didn't work? If not, then it should, and something else may be the problem. — Zirak
– Zirak, Commented Apr 29, 2011 at 14:32

Aaron Silverman · Accepted Answer · 2011-04-29 14:32:39Z

1

Yes. Since this is an array of objects (which is really just an array of memory addresses, you can indeed set them to null as that would be setting the address to 0). However if you have a two dimensional array of a primitive type, such as an int, then you cannot set positions to null.

answered Apr 29, 2011 at 14:32

Aaron Silverman

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2 Comments

Cole Over a year ago

i cannot apply to strings as well then?..so how i can do it.deleting it with for loop?

Dave Costa Over a year ago

It will work fine for String objects. Any standard type that starts with a capital letter is an object (and you should follow this convention for your own classes). Any standard type that starts with a lower-case letter, such as int or double, is a primitive.

user unknown · Accepted Answer · 2011-04-29 14:40:06Z

You need to specify how many elements are in your array, and you don't have to manually set the elemnts to null.

public class Dim2AR
{
    // String [][] xx = new String [][];
    String [][] xx = new String [20][20];

    public void set (int a, int b)
    {
        xx[a][b] = null; 
    }

    public void set (int a, int b, String v)
    {
        xx[a][b] = v; 
    }

    public Dim2AR ()
    {
        check (3, 3);
        set (3, 3);
        check (4, 3);
        set (4, 3, "foo");
        check (4, 3);
    }

    public static void main (String args[])
    {
        new Dim2AR ();
    }

    public void check (int a, int b)
    {
        if (xx[a][b] != null) System.out.println ("> " + xx[a][b]);
        else System.out.println ("-");  
    }
}

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