How to find the elements present in the Array

[Raj Kumar Bindal]

I want to find the elements which i have filled in the array.Suppose,
int A[] =new int[5];
A[0] = 1;
A[4] = 0;
now is there any way i can find out that i have initialized only 2 values.
Exact problem is that if i am iterating through the array, A[1],A[2],A[3] are also initialized to 0 and A[4] was also 0.So, i can't find out that i have filled A[4].
Kindly let me know.

[catherine matthews]

Hi there,

I think the reason why you are getting all the other array elements as 0 is because by default the array is initialized to 0, since it is an Integer.
If it is a String you would get null. I you do or dont specify null it would still give you a null value. See the example below

    
 
public class ArrayTest
{
 public static void main (String args[])
  {
 
   String A[] =new String[5]; 
    A[0] = "a";
    A[4] = null;
 
for (int i=0; i< A.length ; i++)
{
System.out.println(" a[] is " +A[i]);
}
 
    }
}
 

 

Hope i helped you and didnt confuse you.

[Raj Kumar Bindal]

What you are saying is very correct but i want to ask if there is a way to find out the elements which i have initialized.

[Christophe Verré]

public class ArrayTest
{
public static void main (String args[]) {
 
Integer A[] =new Integer[5]; 
A[0] = new Integer(1);
A[4] = new Integer(0);
 
for (int i=0; i< A.length ; i++) {
if ( A[i] != null  )
System.out.println("Value at " + i + " is " + A[i]);
}
}
}

[Jesper de Jong]

Originally posted by Raj Kumar Bindal:
What you are saying is very correct but i want to ask if there is a way to find out the elements which i have initialized.

If you want to do this with an array of int, then the anwer is no. There's nothing special about the array elements that you have not initialized yourself, so there's no way to see if they have been initialized by you.

As Satou shows, you could use an array of Integer object references instead. The elements that you have not initialized will be null.

[Christophe Verré]

Thanks Jesper for the explanation. Sorry for not explaining anything in my post

[Raj Kumar Bindal]

thanks for your answer but it is also not the perfect answer.
I will give you an int array,suppose Array A,and i will not tell you what is there in this array ,that's all and now you have to find out which locations has been filled.
I think you people got what i want to say.

[Christophe Verré]

I think you people got what i want to say.

I think that what I've posted does it.
But if you insist on using 'int' and not 'Integer', then you can't.
Unless you define a special value meaning 'Not Set'. Like -1.

Make sure to also read Jesper's post carefully

[Raj Kumar Bindal]

thanks to you all!!
I got the answer!!