Proposed Rule - Do not create multiple scanners on System.in

Creating multiple scanners on System.in upsets the predictability of program behavior, especially when System.in has been re-directed.

Noncompliant Code Example

import java.util.Scanner;

public class InputLibrary{

   public static int getInt(){       System.out.println("Please enter an int:");       Scanner in = new Scanner(System.in);       return in.nextInt();    }

   public static int getDouble(){       System.out.println("Please enter a double:");       Scanner in = new Scanner(System.in);       return in.nextDouble();    }

}

Compliant Code Example

import java.util.Scanner;

public class InputLibrary{

   private static Scanner in = new Scanner(System.in);

   public static int getInt(){       System.out.println("Please enter an int:");       return in.nextInt();    }

   public static int getDouble(){       System.out.println("Please enter a double:");       return in.nextDouble();    }

}