How to check whether the input is a number or string by using isNan() in groovy

Hello i am a beginner to groovy i am cofused how to check whether the given input is a number or not i tried the following

def a= ' 12.571245ERROR'
if(a.isNan()==0)
{
println("not a number")
}
else
{
println("number")
}

Kindly help me how to use isNan in groovy.I googled it lot but didnt find any result . Thanks in advance

You can try to cast it to number and catch an exception if its not a number

def a= ' 12.571245ERROR'

try {
    a as Double
    println "a is number"
}catch (e) {
    println "a is not a number"
}

Or

if(a instanceof Number)
    println "Number"
else
    println "NaN"

Although keep in mind, in the second way of checking it, it would fail even if a is a valid number but in a String like "123". 123 is Number but "123" is not.