How to exclude empty values from a Vector

[Sharon Cowling]

I need to loop through my Vector and exclude any empty or null values.
The Vector will contain 12 or more values, of which 1 or more may contain the value, but there is a chance that quite a few will be empty, the code below just gives me a null pointer exception.
Can anybody tell me the right way to do this?
for (int i=0;i<locVector.size();i++){
if (locVector.elementAt(i).equals("")|| locVector.elementAt(i) == null){
locVector.removeElementAt(i);
}
}

[Dirk Schreckmann]

Since nobody has said it yet, Welcome to JavaRanch!
It looks like you're having a little bit of confusion concerning what can be done with a null value. As your code demonstrates (by its failure), you can't test an object for equality using the equals(Object) method if the object is null - note the argument to the method can be null, not the object invoking the method.
For your purposes, a quick and easy solution would be to reverse the order of your tests in your if statement. That way, if the component has a null value, then the second test for equality wouldn't be performed on a null value (as the test would short circuit).
Here's some quick example code to consider:

import java.util.Vector ;
 
public class DeleteMe 
{
    private static Vector vector = new Vector() ;
    
    static 
    {
        vector.add( "0" );
        vector.add( "" );
        vector.add( null );
        vector.add( "1" );
        vector.add( "" );
    }
    
    private static void causeNullPointerException() 
    {
        try 
        {
            System.out.println( vector.get( 1 ).equals( "anything" ) );
        }
        catch ( NullPointerException exception ) 
        {
            System.out.println( "yep, caused a null pointer exception" );
        }
    }
    
    private static void displayNullComponentsCount() 
    {
        int count = 0 ;
        
        for ( int i = 0 ; i < vector.size() ; i++ ) 
        {
            if ( vector.get( i ) == null ) 
            {
                count++ ;
            }
        }
        
        System.out.println( "null components count is " + count );
    }
    
    private static void displayEmptyStringCount() 
    {
        int count = 0 ;
        
        for ( int i = 0 ; i < vector.size() ; i++ ) 
        {
            Object component = vector.get( i );
            
            if ( component != null && component.equals( "" ) ) 
            {
                count++ ;
            }
        }
        
        System.out.println( "empty String components count is " + count );
    }
    
    public static void main( String[] args ) 
    {
        causeNullPointerException() ;
        displayNullComponentsCount() ;
        displayEmptyStringCount() ;
    }
}

Making sense?
Good Luck.

[Sharon Cowling]

Thanks for that, silly mistake on my behalf. Now thats sorted I'm still getting the wrong results out of the Vector, entering 2 out of the possible 12 entries, and I'm getting back my 2 values, and 5 empty strings, well they look like empty strings in the database, but I'm testing for that...any other way to test for a Vector element that does not contain a String value?

 
for (int i=0;i<locVector.size();i++){
if (locVector.elementAt(i) == null){
locVector.removeElementAt(i);
} else if (locVector.elementAt(i).equals("")){
locVector.removeElementAt(i);
}
}

[Dirk Schreckmann]

If I'm understanding you correctly, the instanceof operator may be what you'd want to use. So, after your initial removal of null values:

if ( !( vector.get( i ) instanceof String ) ) { 
    vector.remove( i );
}