How to check any two parameters of a function are null

Question

Suppose I have a function that takes three parameters. Of course I could check that any two parameters of this function is null in this way.

returnType function(p1, p2, p3){

  if((p1 == null && p2 == null) || (p2 == null && p3 == null) || (p3== null && p1 == null)){
       return;    
   }

}

But this is rather cumbersome and wouldn't scale for larger number of parameters.

What would be the elegant way to do this?

Thanks in advance.

The way you suggest here as cumbersome won't work regardless of being cumbersome. — Don Roby, Sep 08 '13 at 11:03
i know that, was just being shorter. I didn't write it following a language exactly as you can see. — QuestionEverything, Sep 08 '13 at 11:05
(DUPLICATE)A better formated question which is answered is in link http://stackoverflow.com/questions/271526/avoiding-null-statements-in-java — Srinath Ganesh, Sep 08 '13 at 11:07

score 8 · Accepted Answer · answered Sep 08 '13 at 11:05

8

returnType function(p1, p2, p3){
   Object[] args = {p1, p2, p3};
   if(Collections.frequency(Arrays.asList(args), null) >= 2) {
        return;
   }
}

answered Sep 08 '13 at 11:05

Oleg Pyzhcov

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You should test as `>= 2`. – Ravi K Thapliyal Sep 08 '13 at 11:08
I thought the poster wanted to check if _exactly_ two parameters are null but then realized that's not the case. Thanks, fixed. – Oleg Pyzhcov Sep 08 '13 at 11:10
If you couple your approach with var args... You have the best solution in my opinion. +1 – Ravi K Thapliyal Sep 08 '13 at 11:14

Sergey Kalinichenko · Answer 2 · 2013-09-08T11:13:05.820

But this is rather cumbersome and wouldn't scale for larger number of parameters.

Moreover, this wouldn't compile. You need to add comparison with null for each parameter, like this:

if((p1 == null && p2 == null )
|| (p2 == null && p3 == null)
|| (p3 == null && p1 == null)) ...

If you need to scale to a larger number of parameters, do this:

int count = 0;
if (p1 == null) count++;
if (p2 == null) count++;
if (p3 == null) count++;
// ... and so on
if (count >= 2) {
    ...
}

score 3 · Answer 3 · answered Sep 08 '13 at 11:02

3

Maybe restructure the method to pass a List<Object> or similar and then iterate the list to check the number of nulls.

answered Sep 08 '13 at 11:02

Mike Q

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Gyanendra Dwivedi · Answer 4 · 2020-02-13T16:23:01.450

Pass your parameter as public int someMethod(Object... param){// your code }

You will get the param as array of Object, then iterate through array to check nulls. As soon as your count reaches 2, break the loop and declare a failure.

static int check(Object... param)
{
   int count= 0;
   for (int i = 0; i < param.length; i++)
        // check param[i] and increase count
   if(param[i] == null){
      count++;
   }
   // return count, this is the number of null parameters to the function.
   return count;
}

Edit 1:

If you are new to variable arguments in java, I would recommend to read https://today.java.net/pub/a/today/2004/04/19/varargs.html

Thanks for pointing out, I fixed it and improved the answer as well. — Gyanendra Dwivedi, Feb 13 '20 at 16:26

score 1 · Answer 5 · answered Sep 08 '13 at 11:20

A smart solution with Java 5 is a varargs validation function.

You can create an utility validation function which takes varargs Object arguments, and check if they are all not null.

Then you can iterate on the array and stop the cycle when you find more than two parameters are null.

boolean validate(int maxNull, Object... params) {
    int count = 0;
    if (params == null) {
        return true;
    }
    for (Object param : params) {
        if (param == null) {
            count++;
        }
        if (count >= maxNull) {
            return false;
        }
    }
    return true;
}

Using this utility function you can check all the parameters and also change the strategy of the test when you'll find a more efficient one.

I agree, Ravi: that's a corner case that depends on the needs. Throwing a null pointer exception can be another way. — MPavesi, Sep 08 '13 at 16:07

score 0 · Answer 6 · answered Sep 08 '13 at 11:02

You can always conduct your code in a try block and catch NullPointerException

String foo(Object p1, Object p2, Object p3){
  String bar;
  try {
       bar = p1.toString() + p2.toString();
       return bar;
   } catch (NullPointerException e) {
       return null;
   }
}

upog · Answer 7 · 2013-09-08T11:23:07.223

0

try this just another way of checking,

boolean isAtleastTwoNull = (p1==null )? (p2== null || p3==null): (p2==null && p3==null);

edited Sep 08 '13 at 11:23

answered Sep 08 '13 at 11:14

upog

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How to check any two parameters of a function are null

7 Answers7