Java get the object that is not null

Question

I have an array with 4 objects, and only one of them is not null. I want to call a method, giving that variable as a param.

Block[] b = getIntersectingBlocks(e); // I get 4 Block variables, and only one of them is not null
// ...
Listener.myMethod(notNullBlock); // notNullBlock should be the block out of the array, that is not null

What is the fastest way of doing that, and avoiding if - else statements like this:

if (b[0] != null) {
    Listener.myMethod(b[0]);
} else if (b[2] != null) {
    Listener.myMethod(b[1]);
}
// ...

How do you check if something is not null? Also, an object cannot be null. An array variable (an array element) can reference null. — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Jun 11, 2014 at 3:39
why not just use a for/in loop? then you would only need one if — Bryan
– Bryan, Commented Jun 11, 2014 at 3:47
Is there any particular reason the code is structured to return an empty array save for a single element? — awksp
– awksp, Commented Jun 11, 2014 at 3:47
why not put the whole null check thing inside one big if() with an OR condition — vikeng21
– vikeng21, Commented Jun 11, 2014 at 3:48

Bohemian · Accepted Answer · 2014-06-11 03:48:22Z

3

This doesn't use multiple if and will work for an arbitrary length array:

for (Block block : b)
    if (block != null)
        Listener.myMethod(block);

If more than one Block can be non-null, add a break to prevent the listener being called more than once:

for (Block block : b) {
    if (block != null) {
        Listener.myMethod(block);
        break;
    }
}

answered Jun 11, 2014 at 3:48

Bohemian♦

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Comments

Elliott Frisch · Accepted Answer · 2014-06-11 03:44:39Z

1

If understand your question, you could do it with a massive nested ternary (please don't do this in real code),

final Block notNullBlock = (b == null || b.length != 4) ? null :
    b[0] != null ? b[0] : b[1] != null ? b[1] : b[2] != null ? b[2] :
    b[3];

You could also use a for-each loop (but it requires an if) -

Block notNullBlock = null;
for (Block block : b) {
  if (block != null) {
    notNullBlock = block;
    break;
  }
}

answered Jun 11, 2014 at 3:44

Elliott Frisch

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1 Comment

Bohemian Over a year ago

I was almost going there too, but there are still tests in there, and I don't think it answers the question. I believe he's looking for a general solution that works for an arbitrary length array.

Rod_Algonquin · Accepted Answer · 2014-06-11 03:53:52Z

1

Use for each loop

for(Block bl:bArray){
   if(bl !=null)
    Listener.myMethod(b1);
}

edited Jun 11, 2014 at 3:53

Rod_Algonquin

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answered Jun 11, 2014 at 3:52

Ashish Bhatia

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Comments

Programmer · Accepted Answer · 2014-06-11 04:24:58Z

1

Let say you have an array of Block as below: Block[] blocksArray = {null, null, new Block(), null};

Pass above array to this method:

    private Block provideBlock(Block[] blocksArray)   { 
        for(Block block : blocksArray) {
            block instanceof Block? return block : continue;
        }
    }

Then use returned not null block in your code as:

Block block = provideBlock(blocksArray);
Listener.myMethod(block);

edited Jun 11, 2014 at 4:24

answered Jun 11, 2014 at 4:14

Programmer

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