Warm-up: Monday, February 24

Warm-up: Monday, February 24 • In outputting, what does “\n” do? • In outputting, what is the difference between the System.out.print( ) command and the Serial.out.println( ) command?

Warm-up: Monday, February 24 • In outputting, what does “\n” do? • Goes to the next line; like hitting “enter” • In outputting, what is the difference between the System.out.print( ) command and the Serial.out.println( ) command? • print( ) stays on the same line • println( ) will go to the next line

Arithmetic Operators PAP Computer Science, Cycle 5

8 Mathematical Operators • Addition (+) • Subtraction (-) • Multiplication (*) • Division (/) • Modulus (%) • Exponent (^) • Increment (++) • Decrement (--)

Addition, Subtraction, Multiplication • These operators work identically in programming as in traditional math • 5 + 8  13 • 10 – 4  6 • 4 * 3  12

Division • Works differently for integers (whole numbers) and decimals • If operands are integers, the answer will be an integer • If operands are decimals, the answer will be a decimal • 11 / 2  5 • 11.0 / 2.0  5.5

Modulus (%) • Modulus returns the remainder from division • Example: 26 % 5  1 26 / 5  5

Incrementing (++) • Increases the value of a variable by 1 Example int x = 5; x++; System.out.print(x)  6

Decrementing (--) • Decreases the value of a variable by 1 Example int x = 5; x--; System.out.print(x)  4

Pre- and Post-Incrementing • When incrementing/decrementing, you can put the operator before or after the variable • Example int x = 5; int y = 5; x++; ++y; x  6 y  6

Pre- and Post-Incrementing • Example: int x = 5; int y = x++; x  6 y  5 • Example: int x = 5; int y = ++x; x  6 y  6

Order of Operations

OOO Example 3 * 7 – 6 + 2 * 5 / 4 + 6

OOO Example 3 * 7 – 6 + 2 * 5 / 4 + 6 21 – 6 + 2 * 5 / 4 + 6

OOO Example 3 * 7 – 6 + 2 * 5 / 4 + 6 21 – 6 + 2 * 5 / 4 + 6 21 – 6 + 10 / 4 + 6

OOO Example 3 * 7 – 6 + 2 * 5 / 4 + 6 21 – 6 + 2 * 5 / 4 + 6 21 – 6 + 10 / 4 + 6 21 – 6 + 2 + 6

OOO Example 3 * 7 – 6 + 2 * 5 / 4 + 6 21 – 6 + 2 * 5 / 4 + 6 21 – 6 + 10 / 4 + 6 21 – 6 + 2 + 6 15 + 8

OOO Example 3 * 7 – 6 + 2 * 5 / 4 + 6 21 – 6 + 2 * 5 / 4 + 6 21 – 6 + 10 / 4 + 6 21 – 6 + 2 + 6 15 + 8 23

Warm-up: Tuesday, Feb 25 What does the % operator return? int x = 6; x++; What does ‘x’ equal now?

Creating Variables PAP Computer Science, Cycle 5

Variables • Variables are place-holders for values • Storage locations • They reference a single number, character, or String, and can be called by their name. • Example: • X = 5 • Y = X + 5;

Declaring a Variable • Variables must be declared with two things: • Data type • Name • Initializing a variable (giving it a value) is NOT required when declaring a variable

Declaring/Initializing a Variable • Example 1 int x; x = 5; • Example 2 int x = 5;

Initializing a Variable • Variable name ALWAYS goes on the left x = 5 NOT 5 = x y = x Sets y to whatever is stored in x

Naming a Variable • Names in Java must follow certain rules • Naming conventions hold true for variables, methods, classes, etc • Cannot be a reserved word • int, float, double, char, void, public, static, return • Can only consist of letters, numbers, _, $ • Cannot begin with a number • Case sensitive • X != x VAR != var Test != test

Legal Identifiers • Variable • str • num_of_books • $Amount • integer3 • convert2fahr

Illegal Identifiers (Names) • employee salary • Spaces are not allowed • Hello! • ! is not allowed • one+two • + is not allowed • 2nd • Cannot begin an identifier with a number

Data Types • Data types refer to the type of data that will be stored in the variable • Lets the computer know how much memory it needs to set aside for the variable • Data Types • Int, Short, or Long (whole numbers) • Float or Double (decimals) • Byte (binary byte) • Char (single character) • Boolean (true/false)

Int, Short, Long • Used for whole numbers • Short (16 bits of memory) • -32,768 to 32,767 • Int (32 bits of memory) • -2,147,483,648 to 2,147,483,647 • Long (64 bits of memory) • -263 to 263

Float and Double • Used for decimal point numbers • Float (32 bits) • -3.4 x 1038 to 3.4 x 1038 • 6 to 7 digits of precision (decimal places) • Double (64 bits) • -1.7 x 10308 to 1.7 x 10308 • 15 digits of precision (decimal places)

Byte, Char, Boolean • Byte (8 bits) • Used for binary bytes (B11001101) • Char (16 bits) • Used for characters (‘A’) • Boolean (1 bit) • True or false

Using Variables in Code public class Variables { public static void main(String[ ] args) { int test1 = 90; float test2 = 86.34; int test3 = 23; float sum = test1+test2+test3; System.out.println(“Sum = “ + sum); } }

Warm-up: Wednesday, Feb 26 • Write the code to declare a variable named “number” that contains the number 45.46

Strings PAP-Computer Science, Cycle 5

Strings • List of multiple characters • Also known as • Character array • Character string • String literal • String constant • In Java, String is a special class

String Class • As a class, a String has certain properties and methods • Properties • Length – how many letters in the String? • Letter position • Methods • compareTo • startsWith • endWith

Declaring Strings • Works much the same way as declaring any other variable • Needs data type and a name • Value is optional

Declaring a String String name = “Ms. Alexander”; String message = “Good luck on your test!”; String weather = “It is sunny outside.”;

Example Code - Strings public class Example { public static void main(String[] args) { int value = 56; String str = “Your value is “; System.out.println(str + value); } }

Warm-up: Monday, February 24