how to delete null values/elements from an array

Question

need help again. sorry. how can i remove the null values from my array? here is what i got so far.

int unikCount = 0;
String c = " ";
for (int i = 0; i < a.length; i++) {
    for (int j = 0; j < a.length; j++) {
        if (tempAry[i].equals(tempAry[j])) {
            unikCount++;
        }
        if (unikCount > 1) {
            tempAry[j] = c;
            unikCount = 1;

        }

    }
    unikCount = 0;
}
for (i = 0; i < a.length; i++) {
    if (tempAry[i] != c) {
        unikCount++;
    }

}
System.out.println(unikCount);

for (int i = 0; i < a.length; i++) {
    for (int j = 1; j < a.length; j++) {
        if (tempAry[i].equals(tempAry[j])) {
            if (tempAry[i] == c) {
                count++;
                if (tempAry[j] != c) {
                    count++;
                    tempAry[j] = tempAry[i];

                }
            }
        }
    }

}
count = 0;
for (int i = 0; i < a.length; i++) {
    System.out.println(tempAry[i]);
}

*the remove part is after the "System.out.println(unikCount)". thanks for the upcoming help. by the way, cant use hash and arraylist.

Is there a reason why you can't just create a new array and copy over the non-null values? — Dennis Meng
– Dennis Meng, Commented Oct 4, 2013 at 23:21
Do you mean shorten an array by consolidating it by removing the buckets that have the NULL value in them? And is there a reason why you aren't using a List instead of an array? Lists handily manage this for you. — Drizzt321
– Drizzt321, Commented Oct 4, 2013 at 23:21
Dont compare string with == instead use String.equals(). See Java String.equals versus == — Smit
– Smit, Commented Oct 4, 2013 at 23:22
@Smit Although this is usually correct, in this case seems valid using == since he MAY want to reference every single c and not every " ", what if his array already contains a whitespace? equals will return true for that. — porfiriopartida
– porfiriopartida, Commented Oct 4, 2013 at 23:23

Justin Jasmann · Accepted Answer · 2013-10-04 23:22:27Z

2

You can check for null like this:

if ( null == someObject ) 
{
    // do things
}

There is no way to remove an element from an array and have it shrink automatically. You'll have to use a temporary array to hold values, create an array of a new size and transfer all those items.

A more effective way would be to use a List.

answered Oct 4, 2013 at 23:22

Justin Jasmann

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PM 77-1 · Accepted Answer · 2013-10-04 23:29:51Z

0

Look at your logic (with proper indentation):

if(tempAry[i].equals(tempAry[j])) {                      
    if(tempAry[i] == c) {           
       count++;
       if(tempAry[j] != c) {
           count++;
           tempAry[j] = tempAry[i];

       }
    }
}

It does not make any sense. Why would you check for tempAry[j] != c inside if(tempAry[i] == c) ???

Did you mean to use if...else instead?

answered Oct 4, 2013 at 23:29

PM 77-1

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Hot Licks · Accepted Answer · 2013-10-04 23:43:05Z

0

int j = 0;
Object[] temp = new Object[a.length];
for (int i = 0; i < a.length; i++) {
    if (a[i] != null) {
        temp[j++] = a[i];
    }
}
Object[] newA = new Object[j];
System.arraycopy(temp, 0, newA, 0, j);

If the array is an array of, eg, String, you'd of course change "Object" to "String". And if by "null" one means an empty String, then the if test would be changed appropriately.

answered Oct 4, 2013 at 23:43

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