BIT115: Introduction to Programming

1. BIT115: Introduction to Programming Lecture 8 Instructor: Craig Duckett

3. Assignments 2, 3 • Assignment 2Due TONIGHTLecture 8 by midnight • Monday, October 20th • Assignment 1 Revisiondue Lecture 11 by midnight • Wednesday, October 29th • Assignment 2 RevisionDue Lecture 13 by midnight • Wednesday, November 5th • Assignment 3 Due Lecture 14 by midnight • Wednesday, November 12th(1, 2 or 3-Person Team) • We'll Have a Look at Assignment 3 at the End of Lecture

4. MID-TERM and Buffer Day Mid-Term is LECTURE 10, Monday, October 27th • Please be prompt, and bring a pencil … don’t worry, I’ll supply the paper Buffer Day LECTURE 9, Wednesday, October 22nd • NO LECTURE – Study Session / Homework Session / Q & A / Class Optional

5. Lecture 8 and Going Forward • Lecture 8 ENDSTHE FIRST PHASE OF THE QUARTER --- • WHAT THIS MEANS, AFTER THE MID-TERM: • Less Theory, More Hands-On Work (Less means Less, not No) • Less Hand-Holding, More Trial-and-Error • Less Explanation, More Research & Investigation, More Poking Around For Code, More “Googling It” and More (Occasionally) Aggravation • ----------------------------------------------------------------------- • Becker – Chapters 9.4, 9.5: Input • System.in • The Scanner Class

6. But First… The Quiz!

7. Chapter 9.4, 9.5: Input The Scanner Class • To read input from the keyboard we can use the Scannerclass. • Like Random, the Scannerclass is defined in java.util, so again we will use the following statement at the top of our programs:import java.util.*;orimport java.util.Scanner;

8. The Scanner Class • Scanner objects work with System.in • To create a Scannerobject:Scanner keyboard = new Scanner(System.in); NOTE: Like any other object, keyboard here is a name “made up” by the coder and can be called anything—input, feedIine, keyIn, data, stuffComingFromTheUser, etc.—although it should represent a word most apt to its purpose. In this case we are using keyboard since it seems most apt.

9. Example: ReadConsole.java importjava.util.Scanner; // Or import java.util.*;public classReadConsole{public static void main(String[] args) { Scanner cin = new Scanner(System.in);System.out.print("Enter an integer: ");int a = cin.nextInt();System.out.print("Enter an integer: ");int b = cin.nextInt();System.out.println(a + " * " + b + " = " + a * b); }} A NOTE about Integer Division

10. New Scanner Methods • These are for ints (integers). There are also Scanner methods available for floats, etc, which we'll see later on in the quarter • nextInt() • Does something with the int • hasNextInt() • Checks to see if there is an int • nextLine() • Replaces the int in the keyboard buffer with a newline character so the program won't use the int again

11. Integer Division • Division can be tricky. In a Java program, what is the value of X = 1 / 2? • You might think the answer is 0.5… • But, that’s wrong. • The answer is simply 0. • Integer division will truncateany decimal remainder. • If you are going to divide and need a decimal, then your must use either the floator doubletypes.

12. importjava.util.Scanner; // Or import java.util.*;public classReadConsoleChecked{public static void main(String[] args) { Scanner keyboard = new Scanner(System.in);int a = 0;while (true) // <-- A new kind of while loop we haven’t talked about yet { System.out.print("Enter an integer: ");if(keyboard.hasNextInt()) // Checks to see whether an int has been typed in keyboard { a = keyboard.nextInt();keyboard.nextLine(); // newline flush to “clear the buffer”break; // <-- We haven’t talked about break yet either } else { String next = keyboard.nextLine(); // newline flushSystem.out.println(next + " is not an integer such as 10 or -3."); } }int b = 0;while (true) // <-- A new kind of while loop { System.out.print("Enter an integer: "); if (keyboard.hasNextInt()) { b = keyboard.nextInt();keyboard.nextLine(); // newline flushbreak; } else { String next = keyboard.nextLine(); // newline flushSystem.out.println(next + " is not an integer such as 10 or -3."); } }System.out.println(a + " * " + b + " = " + a * b); }}

13. New Scanner Methods • These are for ints (integers). There are also Scanner methods available for floats, etc, which we'll see later on in the quarter • nextInt() • Does something with the int • hasNextInt() • Checks to see if there is an int • nextLine() • Replaces the int in the keyboard buffer with a newline character so the program won't use the int again

14. A Closer Look: Basic_Keyboard_IO.java

15. A Look at Assignment 3 "The Maze"

16. A Closer Look: The ICE Exercises else { System.out.println("You have not input a valid integer"); keyboard.nextLine(); }