How can I check if a Java Object is a String?

Question

How can I check if an object is of type string?

The better question is: why are you designing code that needs to check? That's usually a bad sign. Polymorphism should be the thing. — duffymo, Jul 20 '12 at 17:11

score 9 · Accepted Answer · answered Jul 20 '12 at 16:17

9

if(object instanceof String)
{
    // Do Stuff
}

answered Jul 20 '12 at 16:17

Baz

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jrad · Answer 2 · 2012-07-21T15:05:17.353

3

Like this:

Integer myInt = 3;
if (myInt instanceof String)
    System.out.println("It's a String!");
else
    System.out.println("Not a String :(");

edited Jul 21 '12 at 15:05

answered Jul 20 '12 at 16:18

jrad

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This is a bad example, as the String is already declared as String, and not as Object (or other super class of String). – Bananeweizen Jul 21 '12 at 06:15
I thought more of declaring an Object, because declaring an Integer or a String makes this a compile time decision. Only for a super class of String (which neither Integer nor String are) this is a runtime decision. But anyway, I removed my down vote. – Bananeweizen Jul 21 '12 at 15:10

score 3 · Answer 3 · answered Jul 20 '12 at 16:20

3

By using the instanceof operator in java:

if(object instanceof String){
    System.out.println("String object");
    // continue your code here
}
else{
     System.out.println("it is not a String");
}

answered Jul 20 '12 at 16:20

cybertextron

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score 1 · Answer 4 · answered Jul 20 '12 at 16:18

1

   if( obj instanceof String ) {}

is a way to check for the object you got is of String

answered Jul 20 '12 at 16:18

kosa

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How can I check if a Java Object is a String?

4 Answers4

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