CSE 1341 Honors

1. CSE 1341 Honors Note Set 04 Professor Mark Fontenot Southern Methodist University

2. Quick Review • Variables • Used to store information that is going to be manipulated during the running of the program • Variables must be declared before they are used • Declaration: dataTypevariableName; • dataTypecan be int, float, double, short, long, byte, boolean, char, String (for now). • Don’t forget the rules for naming variables… What are they??? • Use the = (assignment) operator to assign a value to a variable.

3. Patterns to Notice So Far… • Java is Case Sensitive • Some words have special meanings • Keywords – words/identifiers that are reserved for use by the language • i.e. class, public, int (and other data types), etc. • Complete list on pg 53 of HFJava • Can’t be use as regular (programmer-declared) variable names • Statements end in semicolons public static void main (String [] args) { //not a stmt System.out.println(“Hello ”); //stmt System.out.println(“There”); //stmt } //not a stmt

4. Simple Math • Perform basic arithmetic in code using +, -, *, /, % • +, -, *, / - Standard Meaning • % - modulus operator – remainder of division. • comes in handy in many different situations • Follows PEMDAS rules int var1, var2; var1 = 10; var2 = var1 + 5; var1 = (3 + var2) * 2;

5. Integer vs. Floating Point Math • Integer arithmetic • result can only be an integer • 3 / 4 = ??? • Floating point arithmetic • result can have fractional portion • 3.0 / 4.0

6. Integer vs. Floating Point • How can you tell the difference? • Lower precision values are converted to higher precision values • 3.0 / 4 • 4 is an int • 3.0 is a double • therefore, 4 automatically converted to a double Standard Promotions: Double Float Long Int Short (There are actually many more. We’ll start with these.)

7. Convert F to C public class FtoC { public static void main (String [] args) { double fDeg; double cDeg; fDeg = 56; cDeg = (fDeg - 32) * (5.0/9.0); System.out.print("Conversion: " + fDeg+" F equals "); System.out.println(cDeg + " C."); } }

8. Breakout 1 & 2

9. The Java API • Large “library” of code • Can be used in your programs • Organized in “packages” like java.lang, java.util, etc. • Need to “import” the appropriate package for your task. • java.lang • automatically imported into every program • contains many of the basic features that are not part of the core Java language.

10. Simple Input From The Keyboard • Use an object called Scanner to be able to read from the keyboard • Scanner is in the java.util package. import java.util.*; //gives access to the java.util package public class TestClass { public static void main(String [] args) { Scanner kb = new Scanner(System.in); int value; value = kb.nextInt(); //reads an int after //user presses <enter> //and so on...

11. F to C conversion with Keyboard input. import java.util.*; public class FtoCScanner { public static void main (String [] args) { Scanner kb = new Scanner (System.in); double degF; double degC; System.out.print("Please enter a temp in F: "); degF = kb.nextDouble(); degC = (degF - 32) * (5.0/9.0); System.out.print(degF + "f "); System.out.println("is equal to " + degC + "c."); } …more features of Scanner to come in the future…

12. Breakout 3