Nsryjdtyk

I am new to Java. I am facing an issue now in which I couldn't find the easiest and cleanest way of solving it.

Suppose I have 3 parameters(string) passed to a function(could be a Hashmap too).I want to check if individual variable or combination of variables is not Null and act accordingly.

For example one way to do this is using if-else this way

if(a!=null && b == null && c == null) { 

      //doSomething   

}

 else if(a==null && b!= null && c == null ) { 

     //doSomething 

}

 else if(a==null && b0= null && c != null) { 

     //doSomething 

}

  ......

    //Similarly combination of two variables

 if(a!=null && b != null && c == null) {

     //doSomething 

}

 else if(a!=null && b== null && c != null) { 

    //doSomething

}

 else if(a==null && b!= null && c != null) { 

    //doSomething 

} 

  ......

    //and so on 

    //Similarly combination of three variables

 if(a!=null && b != null && c != null) {

    //doSomething 

}



   ....

How to achieve this kind of situation. I found similar question, but didn't make the code clean. Any help will be appreciated

Write these utility functions and you can compare n terms easily.

public static boolean isAllNull(Object... objects) {

     return Stream.of(objects).allMatch(Objects::isNull);

}



public static boolean isAllNotNull(Object... objects) {

     return Stream.of(objects).allMatch(Objects::nonNull);

}

you can use these functions for n comparisons.

if(isAllNotNull(a) && isAllNull(b,c)) { 

      //doSomething   

}

 else if(isAllNotNull(b) && isAllNull(a,c)) { 

     //doSomething 

}

 else if(isAllNotNull(c) && isAllNull(b,a)) { 

     //doSomething 

}

This is my solution. Note, that you have multiple if...else in one single method. And then you add doSomething. This is going to be terrible to ready and later to realize.

What about to move one single condition into separate method and name it with relative name. Then, lets encapsulate it into Consumer and all of it into a predefined list. Later, if your doSomething will be huge, then you can move from single method to single class, not modifying client code.

This is class, to collect required variable for conditions:

final class Data {



    private final String a;

    private final String b;

    private final String c;

}

Then define one Consumer per on if statement:

Consumer<Data> wonderfulConsumer = data -> {

    if (a != null && b == null && c == null) {

        // do something for wonderful consumer

    }

};



Consumer<Data> badLuckConsumer = data -> {

    if (a == null && b != null && c == null) {

        // do something for bad luck consumer

    }

};

Note, all these consumers could be modified separately (even be in the different classes).

Then in the client code, define list of all known consumers: List<Consumer<Data>> consumers = Arrays.asList(wonderfulConsumer, badLuckConsumer).

And finally your method will be like this and you do not need to change it when you decide to modify or add consumers.

Data data = new Data(a, b, c);

consumers.forEach(consumer -> consumer.accept(data));

If I had to do this , i will do it in the same way that you have done.
but if you dont like that and if you think it is not readable you can do it in this way, i expect lot of negative comments to this answer because this is a bad solution.

 public static void yourMethod(Object a,Object b,Object c)

  {

    int evaluation = howManyNotNull(a,b,c);



    if(evaluation == 0) // all are nulls

    {

      // your code

    }

    else if(evaluation == 1) // only one is not null

    {

      if(a!=null)

      {



      }

      else if(b!=null)

      {



      }

      else

      {

        // c not null

      }

    }

    else if(evaluation == 2) // two variables are not null but other one is null

    {

      if(a==null)

      {



      }

      else if(b == null)

      {



      }

      else

      {

        // c is null, a and b not null

      }

    }

    else 

    {

      // all abc not null

    }



  }



  private static int howManyNotNull(Object a, Object b, Object c)

  {

    return (a==null?0:1) + (b==null?0:1) + (c==null?0:1);

  }

There is extended version of this , assign 3 prime values for a, b , c (example :a=2,b=3,c=5), then use a supportive method like this

private static int convertAvailabilityToInt(Object a, Object b, Object c)

  {

    return (a==null?1:2) * (b==null?1:3) * (c==null?1:5);

  }

if the answer is 1 ,then all are not null .

You can use for example a 3 digit string simulating 3 flags.
You first set it to "000".
Then you check each variable for null, if it is not you will replace the 0 with 1.
Then you could use switch cases to treat each case.