CODEWITHSUNDEEP
javaswitch-statementindexoutofboundsexceptionanonymous-arrays
Blagovest Buyukliev
Blagovest Buyukliev

Reputation: 43508

Anonymous array indexing instead of a switch statement?

In Java, I find the following code much cleaner and easier to maintain than the corresponding bulky switch statement:

try {
  selectedObj = new Object[] {
    objA,
    objB,
    objC,
    objD,
  }[unvalidatedIndex];
} catch (ArrayIndexOutOfBoundsException e) {
  selectedObj = objA;
}

opposed to

switch (unvalidatedIndex) {
  case 0:
    selectedObj = objA;
    break;

  case 1:
    selectedObj = objB;
    break;

  case 2:
    selectedObj = objC;
    break;

  case 3:
    selectedObj = objD;
    break;

  default:
    selectedObj = objA;
}

Is the former considered an acceptable practice? I am aware that it's not the most efficient one as it involves allocating an array and catching an exception. Would it cause something undesirable when unvalidatedIndex is out of range (although the exception is handled)?

If possible, would you suggest something cleaner?

Upvotes: 2

Views: 501

Answers (6)

Jigar Joshi
Jigar Joshi

Reputation: 240908

How about

if(index < arr.length && index >= 0){
    obj = arr[index];
}else{
    obj = defaultValue;
}

Upvotes: 1

L. Cornelius Dol
L. Cornelius Dol

Reputation: 64036

Personally, though I have no doubt some will disagree, I would do:

switch (unvalidatedIndex) {
    case 0 : selectedObj = objA; break;
    case 1 : selectedObj = objB; break;
    case 2 : selectedObj = objC; break;
    case 3 : selectedObj = objD; break;
    default: selectedObj = objA; break;
    }

It's clean, compact, efficient, and really easy to understand.

I would hesitate to include the case 0, that being the default case.

Upvotes: 1

user207421
user207421

Reputation: 310957

Both are antipatterns. Just test the index for range membership yourself. There might be a way to use an enum in many actual cases.

Upvotes: 1

bigGuy
bigGuy

Reputation: 1744

It is not an acceptable practice. Exceptions are for errors handling, not for program flow. Also exceptions are VERY SLOW.

Upvotes: 2

Peeter
Peeter

Reputation: 9382

    int index = 4;

    ArrayList<String> myObjects = Lists.newArrayList("a", "b", "c", "d");
    Object o = index  < myObjects.size() && index >= 0 ? myObjects.get(index) : null;
    System.out.println(o);

Lists comes from Guava.

Upvotes: -1

SLaks
SLaks

Reputation: 887489

Your first approach is fine.

However, it is better to check the index first:

Object[] arr = new Object[] { ... };

if (i < 0 || i >= arr.length)
    i = 0;
selectedObj = arr[i];

Upvotes: 5

Related Questions