User Input

Scanner

The Scanner class (from java.util) is used to get different types of input

We use System.in to read keyboard input:

Scanner myObj = new Scanner(System.in);  // Scanner object
String userInputString = myObj.nextLine();  // method to read user input
int userInputInt = myObj.nextInt(); // another method to read user input

Scanner has a few methods to read input besides .nextInt()

Adding Scanner to Calculator

Remember to print out messages to the user.

public static void main(String[] args) {
  Scanner scanner = new Scanner(System.in);
  System.out.print("Enter a number: ");
  double left = scanner.nextDouble();
  System.out.print("Enter another number: ");
  double right = scanner.nextDouble();
  Calculator calc = new Calculator(left, right);
  System.out.println(calc);
}

What happens if the user does not enter a number?

Practice

Write a Java application to check if a year is leap or regular

Leap years are those that are either:

• divisible by 4 and not 100
• divisible by 400

Write a main static method in the same class that asks for user input, and prints out a message saying whether the year entered is leap or not.