Slide 1
CSCI1226Introduction to Computing Science and Programming
Lecture 6: Midterm Review Tami MeredithProgramming ProcessHow do we
fill in the yellow box?TextEditorCompiler(javac)Interpreter (JVM:
java)UserLibrariesOperating System
(Windows)OutputInputJDKProgramming RequiresIdentification of the
problemUnderstanding it, identifying correct solutionsSolving the
problem:Selecting the data structures, andData Management is the
key hereIdentifying an algorithmControl Flow is the basis of
algorithmsCoding the solutionTesting, debugging, verifying the
solutionWhat is a Program?Programs = Data + AlgorithmsData: the
nouns, the things we manipulateAlgorithms: the verbs, the actions
we performA program manipulates the input (data) to produce the
required output (data)Some Common Data TypesStrings: Sequences of
characters"hi there", "Hello, Bob!", "x", "RESULT"Integers: Whole
numbers-3097, -2, -1, 0, 1, 10, 10340Floating Point Numbers: Things
with a decimal1.0, 3.14, .333, 100000.0000001Booleans: Truth values
for teststrue, false (thats it, just two Boolean
values)IntegersThere are four kinds of integersThe main difference
is the minimum and maximum valuesbyte: -128 to 127short: -32 768 to
32 767int: -2 147 483 648 to 2 147 483 647long: -9 223 372 036 854
775 808 to 9 223 372 036 854 775 807Difference is caused by the
amount of memory used to store each onebyte = 1 byte, short = 2
bytes int = 4 bytes long = 8 bytesVariablesint i;Defines a section
of memory large enough to hold an integer and names that area of
memory "i", the memory contains a random value from whatever it was
used for previouslyi = 5;Stores the value 5 in the area or memory
named "i"int i = 5; Combines 1. and 2.A variable holds one, and
only one, thingA variable always has a value ... if you put nothing
there then assume it has a random value
VariablesVariables describe memory locationsValues are stored in
those locationsIdentifiers name locations
int x = 13; location x 13
Right Hand Side (of =): Use the value stored in the location
(used also when no = in expression)Left Hand Side (of =): Use the
location to store the valueOperatorsStandard math: +, -, *,
/Modulus (Remainder): %Assignment to a variable name uses =Can
change the type of something using a castint x = 1;float y =
(float) x;+ is also string concatenatione.g., "Hi " + "there"
creates "Hi there"
Delimiters" "A string (sequence of zero or more characters)'a'A
character (a single character, never empty){ }A block (sequence of
zero or more statements)/* */A multi-line comment( )A math
expressionA test in a loop or conditionalThe parameters of a method
call The parameters in a method declarationStringsStrings are a
special data type (Strings are actually objects)Ordered and
numbered sequences of charactersIndexed from 0Delimited by double
quotesE.g., "Hello World!", "", "tami"Large library of String
manipulation methods existsString MethodsSee Figure 2.5 in the text
(page 86)length() returns the length of a string (as an
integer)indexOf(string2) returns the index of string2 in string or
-1 if string2 is contained in stringequals(string2) returns TRUE if
string equals string2 otherwise it returns FALSEString sentence =
"Hello programming class";int len = sentence.length();boolean same
= sentence.equals("Good bye!");
ExerciseWrite a program that has a single String variable
containing your name (as 2 words)e.g., String name = "Tami
Meredith";The program will print out your initialse.g., Tami
Meredith's initials are: TM
Solutionpublic class initials { public static void main
(String[] args) {
String name = "Tami Meredith"; int first = 0; int second =
name.indexOf(" ") + 1;
System.out.print(name + "'s initials are: ");
System.out.print(name.charAt(first));
System.out.println(name.charAt(second));
} // end main()} // end class initialsControl is Power!Control
flow is actually very simple:Everything is sequential, unless
...Something is optionalConditional Statements, i.e,. ifSomething
is repeatedLooping Statements, i.e., do, for, whileSomething
complex is broken into simpler partsMethods (and classes,
objects)Programs in JavaPrograms are structured
hierarchically:Programs have 1 or more classesFiles are named after
the classes they containClasses contain 1 or more methodsThe class
that is used to start execution must contain a method named
mainMethods perform 1 or more actionsActions are performed by
statements
About Statements ...Statements are like sentences in a
programming languageStatements usually end with a ";"
(semi-colon)Statements are performed sequentially, one after the
other (generally left to right, top to bottom)For example: x = x +
1;y = 2 * x;System.out.println("Y is " + y); StatementsExpressions
and assignmentse.g., x = 3 * y;Conditional statements to make
choicese.g., if (x == 0) System.exit(0);Loops to repeat thingse.g.,
while (i > 0) System.out.println(i--);Blocks to group statements
into a single statemente.g., { statement1; statement2; statement3;
... }BlocksStatements can be grouped into a blockA block is treated
like a single statement and can be used where a single statement is
expectedBlocks are formed by surrounding a group of statements with
curly braces, "{" and "}"For example: { y = x * 2;
System.out.print("Two times " + x + " is " + y);}
Conditional StatementsConditionals make a choice of whether a
statement should be executed:Syntax: if (test) statementWhen test
evaluates to true, statement is executedstatement is singular, a
block must be used to do more than one thing when test is
trueAlternate Syntax:if (test) statement1 else statement2If test is
equal to true then do statement1If test is equal to false then do
statement2Note that there is no ";" at the end of the
conditionalLoopsExecutes a statement more than onceSyntax:while
(test) statementEvaluate testIf test is equal to true, do step 3,
otherwise donePerform statement then go back to 1Note that
statement is singular and that the loop does not end with a ";"
(but statement does)
Example // Code fragment, counts from 0 to // the value "stop"
input by the user
int count = 0;int stop = user.nextInt();
while (count
