The operator * is undefined for the argument

Hello, I'm new to this website, and new to programming.
I'm trying to write a simple code that will multiply height and width(Excuse my English, It's not my native language)
But I'm getting the error "The operator * is undefined for the argument"
Here's my code

import java.util.Scanner;
class Calc {

	public static void main(String args[]){
		
		
		double answer;
		System.out.println(" enter width");
		Scanner width1 = new Scanner(System.in);
		
		System.out.println("enter height");
			Scanner height1 = new Scanner(System.in);	
			answer = height1 * width1;
			
			
	}
}

Any suggestions?