private static Double getDouble() {
		Boolean flag;
		double numDouble = 0.0;
		do {
			Scanner scanner = new Scanner(System.in);
			try {
				numDouble = scanner.nextDouble();
				flag = true;
			} catch (Exception e) {
				flag = false;
				System.out.println("Input type mismach!");
				System.out.print("Please input in Double: ");
			}
		} while (!flag);
		return numDouble;
	}