import java.util.Scanner;
public class Test{
  public static void main(String[] args){
    Scanner scan=new Scanner(System.in);
Double doub;
while(true){
System.out.println("Input Something: ");
try{
doub=scan.nextDouble();
break;
}catch(Exception e){
System.out.println("Error!");
scan = new Scanner(System.in);
continue;
}

}

  }
}