package test; import com.google.common.base.Optional; import com.google.common.base.Preconditions; public class GuavaTester { public static void main(String args[]){ GuavaTester guavaTester = new GuavaTester(); System.out.println(guavaTester.sqrt(-3.0)); } public double sqrt(double input) throws IllegalArgumentException { Preconditions.checkArgument(input > 0.0, "Illegal Argument passed: Negative value %s.", input); return Math.sqrt(input); } }