1. Lec 7 Using Static Class Methods

2. Today We work with static utility methods of a class We learn how JavaDocs can help us figure out how to use them

3. 3 Different Kinds of Classes 1.Application Class – what we've been doing – Has public static void main ( String [] args) 2.Instantiable Class – use to make objects from – String, Scanner 3.Classes with only static utility methods – like Math class

4. 3 Different Kinds of Classes -- I Application Class – what we've been doing – has public static void main(String [] args) – where program begins execution – where we develop solutions to lab problems create variables, objects that help us read input, compute answers, display results

5. 3 Different Kinds of Classes -- II Instantiable Class – used to make objects from – SO FAR ONLY: String, Scanner To use an Instantiable class we must – Declare a variable of that class type String message; Scanner myUserInput; – Instantiate a new object message = new String("hello"); myUserInput = new Scanner(System.in); – Use associated methods (name of object '.' method) message.trim(); myUserInput.nextInt();

6. 3 Different Kinds of Classes -- III Classes with static utility methods – We never "instantiate" these classes – Math class (Math.random(), Math.round() ) – refer to the class name '.' method name We can get lots of help from these IF we learn how to read the JavaDocs manuals on them

7. Class NumericalStuff Demo "Helper" for working with numbers – finding prime numbers, dividing – Home made by Professor Kowalczk Javadocs for NumericalStuffNumericalStuff Lets study some of the method documentation:

8. NumericalStuff -- findPrime static: means it's a static utility method – will not be associated with an object – have to invoke by "Name of Class" NumericalStuff.findPrime

9. NumericalStuff -- findPrime int: means it's going to give you an integer back – you need a variable to receive it: int myPrime = NumericalStuff.findPrime... – OR you can print it out System.out.println("a prime is " + NumericalStuff.findPrime... )

10. NumericalStuff -- findPrime findPrime: the name of this particular method

11. NumericalStuff -- findPrime int n: means you must give it an integer in parens – int myPrime = NumericalStuff.findPrime (5); – System.out.println("a prime is " + NumericalStuff.findPrime(12));

12. Given this NumericalStuff method doc Which is/are using it correctly? boolean x = isPrime ( 23); int x = NumericalStuff.isPrime(23); if (NumericalStuff.isPrime(23)){.... boolean x = NumericalStuff.isPrime(3.14159);

13. Using Class OtherStuff... How would you show the current Time ? How would you save the 10th dictionary word?

14. Using Class StringUtil... How to determine what is the 5 th letter of "centaur" ?

15. Using Class Coin: One other return type -- void Means it doesn't return anything Use it on a line by itself Coin.dispenseDime(true); // prints a dime, beeps Coin.dispenseDime(false); // prints, doesn't beep

16. Lab 7 Making change with Coin Class Ask for amount of change requested Find how many coins that is (using Coin class) dispense Quarters until no more left – use a while loop with Coin.dispenseQuarters inside dispense Dimes until no more left – use a while loop with Coin.dispenseDimes inside and so on with nickels and pennies maybe disable "beep" while debugging!