null comparison

[Tyler Jordan]

I have a value in an array that has certain values that are null when I do a println command on them. I need to do an statement that compares these value to null. (either that it equals or doesn't equal null). I have tried the equals method and the operators, but neither compares the values correctly. Is this a special case in Java? How should I compare these?

         int n = 15;
         readThis = new ReadAFile();
         String[] ipArray = readThis.getIpArray(n);
         for (int i=0; i < n; i++) {
             System.out.println("Main Program: " + ipArray[i]); // prints some values as null
         }
         for (int s=0; s < n; s++) {
             String testThis = ipArray[s];
             if (ipArray[s].equals(null)) {     // Loop should stop if value is null
                 n = s;                   
             }
             else {
                 //Continue counting
             }
         }

[Chris Harris]

Hi Tyler,
Compare null values are null do the following instead of using the equals method:
if (ipArray[s] == null) //is null
if(ipArray[s] != null) // if not null.

You can't do:
ipArray[s].equals(null)
as there is no instance created for the value so there will not be a pointer to the object. If you do this you will get a NullPointerException if ipArray[s] is null.
Hope that helps. Let us know if you have any more problems.
Chris