CSCI 1226 FALL 2015 MIDTERM #1 REVIEWS

Types of computers:Personal computersEmbedded systems Servers

Hardware: I/O devices: mice, keyboards, monitors, etcCPU (Central Processing Unit)Memory, Main/Primary vs secondary

COMPUTERS

Exam tip!Examples of each type?

Exam tip!What are the differences?

Exam tip!Examples of each type?

Software:Data & instructions

Algorithm Pseudo-code

Data hierarchy: 8 bits byte 1 or more bytes data value (field) 1 or more data values/objects object (record) data may be stored on secondary memory (file)

…COMPUTERS

Exam tip!What are the differences?

Exam tip!An object can contain other objects!

IDE: Integrated Development EnvironmentAlgorithms, pseudo-codeVariables:

Data types: int/double/String/boolean/charDeclaration e.g.) int a; String name = “name”;Naming rules and conventions

Math and special assignment operators+, -, *, /, %+=, -=, *=, /=. %=++, --

JAVA PROGRAMMING BASICS

Exam tip!Declare variables given description:e.g.) the number of words entered by the userwhether the user is 65 or older

Output: System.out.println() and System.out.print()

Print spaces With or without quotes Concatenation (using +, with math expressions, etc)

User input: Scanner class: instantiation, import, etcnext(), nextLine(), nextInt(), nextDouble(), etcUse nextLine() to

flush the input buffer

…JAVA PROGRAMMING BASICS

Exam tip!How to pause a program using nextLine()?

Exam tip!Print all values in one line or each value in one line

Exam tip!Write code to read 2 Strings and a number and ignore the rest: Jimmy Smith 45 ignore mee.g.) review A01

SYNTAX ERROR: NETBEANS

NetBeans notices syntax errors right away look for red squiggle and in margin

mouse over the to see the explanation

LOGIC ERROR

Compiler will not notice!System.out.println("A length by width"

+ "rectangle has an area of area.");Program just does the wrong thing

hopefully you can tell from the output!

→ x / (a + b) → (3 / 5) * (a + b) → k / (2 * a) + 1 / (3 – b) → -a / (3 – b) + 5 * b

MATH EXPRESSIONS

Exam tip!Translate regular math expressions into Java math expressions.

Syntax: if, if-else, if-else if, if-else if … else

Comparison operators==, !=, <, >, <=, >=

Logical operators&& (AND), || (OR), ! (NOT)

CONDITIONALS

Exam tip!Less/larger than or equal to always have “=“ after “<“ or “>”

Sequential and nested if-else:Convert one to the other

What’s the output?:

What’s the code?Possible outcomes:outcome #1: A, B, C, E, Foutcome #2: A, D, E, F

… CONDITIONALS

System.out.print(“A”);if (. . .){ System.out.print(“B”);}if (. . .){ System.out.print(“C”); if (. . .) { System.out.print(“D”); } else { System.out.print(“E”); }}

Can save the answer to a comparisonuse a boolean variableboolean workedOvertime = (hours > 40);

you don’t need parentheses, but it ’s easier to read

E.g.) Write Boolean expressions for whether… x is greater than 0 and y is less than 5 x is greater than zero or y is equal to z it’s not the case that x is greater than the product of y

and z

boolean VARIABLES

Exam tip!“whether” boolean

Break complex expressions downboolean failedMidterm = (midtermGrade < 50);boolean failedFinal = (finalGrade < 50);boolean failedBothTests = failedMidterm && failedFinal;

String comparisons (all return boolean values)oneString.equals(anotherString)oneString.equalsIgnoreCase(anotherString)oneString.startsWith(anotherString)oneString.endsWith(anotherString)

… boolean VARIABLES

Exam tip!boolean a = true, b = false, c = false;!aa && b (a || c) && (!b && !c) (a && !b) || c

STRING.TOUPPERCASE/TOLOWERCASE

Ask a string for upper/lower case versionSystem.out.println(“Do you want fries?”);String answer = kbd.next(); kbd.nextLine();String upperAnswer = answer.toUpperCase();if (upperAnswer.startsWith(“Y”))

…now accepts “Yes”, “yes”, “Yeah, “yup”, …

upperAnswer is “YES”, “YES”, “YEAH”, “YUP” answer is still “Yes”, “yes”, “Yeah”, “yup”

for and while loopsConvert between them

Loop structure Initialize, test/condition, update, process

LOOPS

for (initialize; test; update){

process;}

initialize;while (test) {

process;update;

}

Exam tip!When asked for an algorithm, make sure to include all these 4 steps!

Write loops to:Calculate sum, average, max, min, of numbersWhen to stop?

Negative number Yes/no

Track the variable’s values: What’s the output of the program?

… LOOPS

a = 1;a++;b = a + 6;b--;c = b * 5;c += a;a *= 10;b /= 2;c %= 4;a *= b + c;S.O.Pln(a + “:” + b + “:” + c);

Exam tip!Write the loops to find these values!

Exam tip!Be able to write a loop that stops for these!

public static final data-type CONST_NAME = valueNaming conventions

variableNameConventionCONSTANT_NAME_CONVENTION

NAMED CONSTANTS

DIVIDING INTEGERS & DOUBLES

Java uses / for both int and double division15 / 2 is 7 because 15 and 2 are both int15.0 / 2.0 is 7.5 because 15.0 & 2.0 are doubles

“Mixed” expressions use double division15.0 / 2 is 7.5; 15 / 2.0 is 7.5

(double) says use the double version of this (double)15 / 2 is 7.5; 15 / (double)2 is 7.5

If sum is 17, then (double)sum is 17.0but sum is still an int (17); it doesn’t change!

CHANGING DOUBLES TO INTS

Can also change the other wayuse (int) in front of a double value/variabledouble price = 15.99;int dollars = (int)price;int cents = (int)(100 * (price – dollars));System.out.println(dollars + " dollars and "

+ cents + " cents.");

NOTE: it doesn’t round off; it truncates!15 dollars and 99 cents.

To Round off, use: int approxDollars = (int)Math.round(price);

Loops with Conditionalswhile (num >= 0) { // say whether num is divisible by 5 if (num % 5 == 0) { System.out.println(num + “ is divisible by 5.”); } else { System.out.println(num + “ is not divisible by 5.”); } // get next number num = kbd.nextInt();}

NESTED STRUCTURES

if inside if:System.out.println(“A”);if (condition1) { System.out.println(“B”); if (condition2) { System.out.println(“C”); }}

… NESTED STRUCTURES

possible output:AABABC

pattern:always Asometimes Bwhen B, sometimes C

Rewrite sequential-if to cascading-if

… NESTED STRUCTURES

if (age < 18) {System.out.print(“Child”);

}if (age >= 18 && age < 65) {

System.out.print(“Adult”);}if (age >= 65) {

System.out.print(“Senior”); }

if (age < 18) {System.out.print(“Child”);

} else if (age < 65) {System.out.print(“Adult”);

} else {System.out.print(“Senior”);

}

Loops inside loops:Draw a rectangle:

Get w, h, and char from user

Conditionals inside loops:Repeated menu with switch

… NESTED STRUCTURES

Inside loopsInside if-elseInside method (variables and parameters)Inside class (instance and class variables)

SCOPES OF A VARIABLE/PARAMETER