Groovy: check at run time if object is a String

Question

I'm about to overload the leftShift operator and wanted to know how to check if the given parameter "other" is a String?

def leftShift(other){
    if(other.getClass() instanceof String){
        println other.toString() + " is a string!"          
}

But this doesn't work.. Can anybody help me?

Answer 1

You can use the test that you would normally use in Java.

def leftShift(other) {
    if(other instanceof String) {
        println "$other is a string!"
    }
}

When you call other.getClass() the result class is java.lang.Class instance which you could compare against String.class. Note other can be null in which the test "other instanceof String" evaluates to false.

UPDATE:

Here's a simple case that creates a Groovy GString instance which is not a string instance:

def x = "It is currently ${ new Date() }"
println x.getClass().getName()
println x instanceof String
println x instanceof CharSequence

Outputs:

It is currently Thu Aug 21 15:42:55 EDT 2014
org.codehaus.groovy.runtime.GStringImpl
false
true

GStringImpl extends GString which has methods that make it behave as a String object and implements CharSequence interface as does the String class. Check if other object is CharSequence which is true if object is a String or GString instance.

def leftShift(other) {
    if(other instanceof CharSequence) {
        println "$other is a string!"
    }
}

Answer 2

It is

if (other.getClass() == String)