How to check whether an Object is String or String Array in java?

Question

A method is returning a Object or Object[] of type String but if I am casting with String[], it is giving class cast exception when it contains single string. How can i resolve this?

Is there any way to check whether it contains String or String[]?

Jon Skeet · Accepted Answer · 2010-11-22 09:51:13Z

26

Sure, use the instanceof operator:

if (x instanceof String) {
  ...
}

if (x instanceof String[]) {
  ...
}

etc. It's not ideal to have to do this, mind you... is there any way you could redesign your API to avoid this?

answered Nov 22, 2010 at 9:51

Jon Skeet

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2 Comments

Riduidel Over a year ago

Due to object orientation concerns. The very fact of using instanceof is equivalent, in this case, to saying "my method could have returned String[] in all cases (as a String can always be put in a String[1]), but as I was not smart enough to do it, i prefered to return anything and let you cope with it."

extraneon Over a year ago

The easiest way to change the API is to always return a String[], with in stead of the String a String[] of size 1.

Michael Borgwardt · Accepted Answer · 2010-11-22 10:02:28Z

7

Rewrite the method to always return String[], even when there's only a single one.

Better yet, have it return List<String> and use Collections.singletonList() for the single-element case.

answered Nov 22, 2010 at 10:02

Michael Borgwardt

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