1. CMSC 150 INTRODUCTION TO COMPUTING CS 150: Fri 13 Jan 2012

2. Variable Declarations  Use to request space in RAM to store values  Syntax:type variableName;  Types:  int : whole number (e.g., 0, 1, 100, 1234)  double :real-valued number (e.g., 3.14159)  char :one character (e.g., ‘A’, ‘9’, ‘q’)  boolean :true or false  String :character sequence (e.g., “Jason”)

3. Variable Declarations  Use to request space in RAM to store values  Syntax:type variableName;  Types:  int : whole number (e.g., 0, 1, 100, 1234)  double :real-valued number (e.g., 3.14159)  char :one character (e.g., ‘A’, ‘9’, ‘q’)  boolean :true or false  String :character sequence (e.g., “Jason”) primitive types

4. Variable Declarations  Use to request space in RAM to store values  Syntax:type variableName;  Types:  int : whole number (e.g., 0, 1, 100, 1234)  double :real-valued number (e.g., 3.14159)  char :one character (e.g., ‘A’, ‘9’, ‘q’)  boolean :true or false  String :character sequence (e.g., “Jason”) class type

5. Variable Declarations  Use to request space in RAM to store values  Syntax:type variableName;  Examples :  int numberOfVictims;  double minutesUntilDemise;  char jasonsFirstInitial;  boolean isKevinBaconStillAlive;  String finalPleaForMercy;

6. In RAM int numberOfVictims; double minutesUntilDemise; char jasonsFirstInitial; boolean isKevinBaconStillAlive; String finalPleaForMercy; numberOfVictims minutesUntilDemise jasonsFirstInitial isKevinBaconStillAlive finalPleaForMercy your program in memory your program in memory

7. Assignment Statements  Use to put values into variables  Syntax:variableName = expression;  Examples :  numberOfVictims = 13;  minutesUntilDemise = 2.1;  jasonsFirstInitial = ‘J’;  isKevinBaconStillAlive = false;  finalPleaForMercy = “Help Me!”; literals (type must match variable type ) literals (type must match variable type )

8. In RAM numberOfVictims = 13; minutesUntilDemise = 2.1; jasonsFirstInitial = ‘J’; isKevinBaconStillAlive = false; finalPleaForMercy = “Help Me!” numberOfVictims minutesUntilDemise jasonsFirstInitial isKevinBaconStillAlive finalPleaForMercy your program in memory your program in memory 13 2.1 J false Help Me!

9. Declaration + Assignment  Combine into a single statement  Syntax:type variableName = expression;  Examples :  int numberOfVictims = 13;  double minutesUntilDemise = 2.1;  char jasonsFirstInitial = ‘J’;  boolean isKevinBaconStillAlive = false;  String finalPleaForMercy = “Help Me!”;

10. Assignments & Expressions numberOfVictims = 13; numberOfVictims = numberOfVictims + 1; evaluate right-hand side value: 13 evaluate right-hand side value: 13 numberOfVictims minutesUntilDemise

11. Assignments & Expressions numberOfVictims = 13; numberOfVictims = numberOfVictims + 1; 13 numberOfVictims minutesUntilDemise 13

12. Assignments & Expressions numberOfVictims = 13; numberOfVictims = numberOfVictims + 1; numberOfVictims minutesUntilDemise evaluate right-hand side value: 13 + 1 evaluate right-hand side value: 13 + 1 13

13. Assignments & Expressions numberOfVictims = 13; numberOfVictims = numberOfVictims + 1; 14 numberOfVictims minutesUntilDemise 14

14. Assignments & Expressions numberOfVictims = 13; numberOfVictims = numberOfVictims + 1; numberOfVictims = numberOfVictims + 7; // party! numberOfVictims minutesUntilDemise evaluate right-hand side value: 14 + 7 evaluate right-hand side value: 14 + 7 14

15. Assignments & Expressions numberOfVictims = 13; numberOfVictims = numberOfVictims + 1; numberOfVictims = numberOfVictims + 7; // party! 21 numberOfVictims minutesUntilDemise 21

16. Incrementing  Increment : add one to a variable  Three ways:  numberOfVictims = numberOfVictims + 1;  numberOfVictims += 1;  numberOfVictims++;  All result in value increasing by one

17. Expressions  Numerical operators:  +−*/%  Examples of expressions:  3.14159 + 2  (11 – 3) * 4  2 / 4  2.0 / 4  4 % 3  m * (c * c)

18. Expressions  Numerical operators:  +−*/%  Examples of expressions (with variables):  double piPlusTwo= 3.14159 + 2;  double thirtyTwo= (11 – 3) * 4;  double zero= 2 / 4;  double oneHalf= 2.0 / 4;  double remainder= 4 % 3;  double e= m * (c * c);

19.  Expression takes on type of largest-storage operand in expression  Examples of expressions (with variables):  double piPlusTwo= 3.14159 + 2;  double thirtyTwo= (11 – 3) * 4;  double zero= 2 / 4;  double oneHalf= 2.0 / 4;  double remainder= 4 % 3;  double e= m * (c * c); Expression Type

20. Division  Works differently for integers vs. floating-point  Examples:  8.0 / 3.0  gives true floating-point result  8 / 3  gives integer quotient  8 % 3  gives integer remainder

21. Be Wary  double myShare = (1/2) * inheritance;  double onePointSixRepeat = (double)(5 / 3);  double threeFifths = 3/5;  double wormHole = someValue / threeFifths;

22. Strings & String Methods  String homerSez = “Donuts. Is there anything they can’t do?”;  0123456789112345678921234567893123456789  0 0 0  int quoteLength= homerSez.length();// 40  char firstChar= homerSez.charAt( 0 );// ‘D’  char period= homerSez.charAt( 6 );  char questionMark= homerSez.charAt( 39 );  char eye = homerSez.charAt( homerSez.indexOf( ‘I’ ) );  String donutsCap= homerSez.substring(0, 6);// “Donuts”  String donuts= donutCap.toLowerCase();// “donuts”  String nuts = donuts.substring( 2 );// 2 to end  String nutsCubed = nuts + “ ” + nuts + “ ” + nuts + “!”;

23. Strings & String Methods  String homerSez = “Donuts. Is there anything they can’t do?”;  0123456789112345678921234567893123456789  0 0 0  int quoteLength= homerSez.length();// 40  char firstChar= homerSez.charAt( 0 );// ‘D’  char period= homerSez.charAt( 6 );  char questionMark= homerSez.charAt( 39 );  char eye = homerSez.charAt( homerSez.indexOf( ‘I’ ) );  String donutsCap= homerSez.substring(0, 6);// “Donuts”  String donuts= donutCap.toLowerCase();// “donuts”  String nuts = donuts.substring( 2 );// 2 to end  String nutsCubed = nuts + “ ” + nuts + “ ” + nuts + “!”;

24. Digits  int one = 1;  char uno = ‘1’;  String ein = “1”;  All are different  Only one contains the integer value 1  1 + 1// 2  ‘1’ + ‘1’// 98 (more on this later)  “1” + “1”// “11”

25. Comments  Allow you to annotate your programs  Two options:  inline // this is an example of an inline comment  block /* this is an example of a block comment */  Java does not execute comments  Use to describe (in English) what your code does  Also use to (temporarily) disable parts of code

26. public class ClassWithComments { public static void main( String[] args ) { int numberOfVictims = 13; // number of people Jason has greeted double minutesToDemise = 2.1; // mins from start of movie to 1st death // Jason just met another person, so add one to # of victims numberOfVictims = numberOfVictims + 1; // Jason crashed a party, so really bump the victim count numberOfVictims = numberOfVictims + 7; /* Let’s comment out the Kevin Bacon code for now... Turns out that was just a dream sequence, but we might need this code later! // Jason killed Kevin Bacon’s character numberOfVictims = numberOfVictims + 1; */ …

27. // Author: Kyra Sedgwick (you may need to search for the reference…) // Date: 13 Friday 2012 // Purpose: This program keeps count of the number of victims of the // “protagonist” Jason from the slasher movie “Friday The 13th”, // along with some other interesting movie trivia. public class ClassWithComments { public static void main( String[] args ) { int numberOfVictims = 13; // number of people Jason has greeted double minutesToDemise = 2.1; // mins from start of movie to 1st death // Jason just met another person, so add one to # of victims numberOfVictims = numberOfVictims + 1; // Jason crashed a party, so really bump the victim count numberOfVictims = numberOfVictims + 7; …

28. /* Author: Kyra Sedgwick Date: 13 Friday 2012 Purpose: This program keeps count of the number of victims of the “protagonist” Jason from the slasher movie “Friday The 13th”, along with some other interesting movie trivia. */ public class ClassWithComments { public static void main( String[] args ) { int numberOfVictims = 13; // number of people Jason has greeted double minutesToDemise = 2.1; // mins from start of movie to 1st death // Jason just met another person, so add one to # of victims numberOfVictims = numberOfVictims + 1; // Jason crashed a party, so really bump the victim count numberOfVictims = numberOfVictims + 7; …