Review by Mr. Maasz, Summary of Chapter 2: Starting Out with Java

 Variables are names (often called “identifiers”) for memory locations.  Just as there are many different types of “information” in math or English, there are many types of data in computer memory  Primitive data types are called this because they cannot be used to create “objects”  Data types: Since numbers come in several flavors like whole numbers, fractional numbers, positive or negative, even very larger or very small numbers  Numeric data types are:  int for whole numbers (integers)  Real numbers (float or double)  Scientific notation numberes Java OOP Programming 2

Two data types related to text: 1. String – literally a “list” of characters, but with methods that contribute to manipulating each String, for example: toUpper( ) toLower( ) 2. char - holds only one character at a time 3. Unicode: a code or numeric representation that uses numbers to represent numbers, symbols, and letters. Includes over 65K characters for other languages, even Greek and mathematics symbols. Data TypeSize (mem- bytes) Range byte1 byteInteger from to 127 short2 bytesIntegers in the range from - 32,768 to 32,767 int4 bytesReally small to really large nos. long8 bytesHUGE numbers float4 bytes-3.4E-38 to 3.4E38 double8 bytes-1.7E-308 to 1.7E308 Java OOP Programming 3

 Integer types hold “whole” numbers  Basic declaration has syntax: int ;  Declaration and Initialization looks like: int age = 15; // age is 15 Read as “age gets the value of 15” Java OOP Programming 4 Data TypeSize (mem- bytes) Range byte1 byteInteger from -128 to 127 short2 bytesIntegers in the range from - 32,768 to 32,767 int4 bytesReally small to really large nos. long8 bytesHUGE numbers

OUTPUT : We have made a journey of 105 miles. It took us 120 minutes. Our account balance is $-20 About days ago Columbus stood on this spot. // This program has variables of several of the integer types. public class IntegerVariables { public static void main(String[] args) { int checking; // Declare an int variable named checking. byte miles; // Declare a byte variable named miles. short minutes; // Declare a short variable named minutes. long days; // Declare a long variable named days. checking = -20; miles = 105; minutes = 120; days = ; System.out.print("We have made a journey of " + miles); System.out.println(" miles."); System.out.println("It took us " + minutes + " minutes."); System.out.println("Our account balance is $" + checking); System.out.print("About " + days + " days ago Columbus "); System.out.println("stood on this spot."); } Java OOP Programming 5

OUTPUT : We have made a journey of 105 miles. It took us 120 minutes. Our account balance is $-20 About days ago Columbus stood on this spot. // This program has variables of several of the integer types. public class IntegerVariables { public static void main(String[] args) { int checking; // Declare an int variable named checking. byte miles; // Declare a byte variable named miles. short minutes; // Declare a short variable named minutes. long days; // Declare a long variable named days. checking = -20; miles = 105; minutes = 120; days = ; System.out.print("We have made a journey of " + miles); System.out.println(" miles."); System.out.println("It took us " + minutes + " minutes."); System.out.println("Our account balance is $" + checking); System.out.print("About " + days + " days ago Columbus "); System.out.println("stood on this spot."); } Java OOP Programming 6 Single line comment Class header: public – can be access by other projects/classes Class – name of the container, keyword IntegerVariables – programmer created class name Left brace, begin class definition Header for main method, static defined page 55

public class IntegerVariables { public static void main(String[] args) { int checking;. Static: (Java Methods: as define on page 55,) “indicates that the method main is not called for any particular object: it belongs to the class as a whole.” A Java app can have only one main. Java OOP Programming 7 Header for main method,

OUTPUT : We have made a journey of 105 miles. It took us 120 minutes. Our account balance is $-20 About days ago Columbus stood on this spot. // This program has variables of several of the integer types. public class IntegerVariables { public static void main(String[] args) { int checking; // Declare an int variable named checking. byte miles; // Declare a byte variable named miles. short minutes; // Declare a short variable named minutes. long days; // Declare a long variable named days. checking = -20; miles = 105; minutes = 120; days = ; System.out.print("We have made a journey of " + miles); System.out.println(" miles."); System.out.println("It took us " + minutes + " minutes."); System.out.println("Our account balance is $" + checking); System.out.print("About " + days + " days ago Columbus "); System.out.println("stood on this spot."); } Java OOP Programming 8 Three process: Input, output, processing, Declaration of variables first Assignment second Output is last Data type: int (whole numbers) Variable name: checking Data type: byte, Variable name: miles Data Type: short, Variable minutes Data Type: long, Variable: days

OUTPUT : We have made a journey of 105 miles. It took us 120 minutes. Our account balance is $-20 About days ago Columbus stood on this spot. // This program has variables of several of the integer types. public class IntegerVariables { public static void main(String[] args) { int checking; // Declare an int variable named checking. byte miles; // Declare a byte variable named miles. short minutes; // Declare a short variable named minutes. long days; // Declare a long variable named days. checking = -20; miles = 105; minutes = 120; days = ; System.out.print("We have made a journey of " + miles); System.out.println(" miles."); System.out.println("It took us " + minutes + " minutes."); System.out.println("Our account balance is $" + checking); System.out.print("About " + days + " days ago Columbus "); System.out.println("stood on this spot."); } Java OOP Programming 9 Three process: Input, output, processing, Declaration of variables first Assignment second Output is last Assignments second; checking “gets value” 20 minutes gets 120 miles “gets” 105 Days “gets” the value of by the assignment op

OUTPUT : We have made a journey of 105 miles. It took us 120 minutes. Our account balance is $-20 About days ago Columbus stood on this spot. // This program has variables of several of the integer types. public class IntegerVariables { public static void main(String[] args) { int checking; // Declare an int variable named checking. byte miles; // Declare a byte variable named miles. short minutes; // Declare a short variable named minutes. long days; // Declare a long variable named days. checking = -20; miles = 105; minutes = 120; days = ; System.out.print("We have made a journey of " + miles); System.out.println(" miles."); System.out.println("It took us " + minutes + " minutes."); System.out.println("Our account balance is $" + checking); System.out.print("About " + days + " days ago Columbus "); System.out.println("stood on this spot."); } Java OOP Programming 10 Three process: Input, output, processing, Declaration of variables first Assignment second Output is last System.out.println( ) Method println displays strings from what is between ( )

 Dollar amounts or precise measurements cannot be expressed as “int”egers  Numbers that allow fractional values are called floating-point numbers  Starting Out With Java, Page  Two floating point data types:  Float – single precision (4 bytes) store floating-pt numbers with 7 digits of accuracy  Double – double precision  Store floating-point with 15 digits of accuracy  Code listing Sale.java Java OOP Programming 11

Code Examples: float number; number = 23.5; // error Correct example: float number; number = 23.5F; // ABOVE IS GOOD  If you use “floating point” literals in your source code,  Java is a “strongly typed” language, will not allow loss of precision  Floating point literals are considered double  Use an “F” capital letter to force (called a cast) conversion. Java OOP Programming 12

 FLOATING POINTS expressed in E notation  Pg 53 Java OOP Programming 13

 boolean data type:  Variables that can only hold the values of either  True  False  Page 54 Java OOP Programming 14

 Used to store character data, one letter, symbol, or numeric character  Character literals are surrounded by single quotation marks.  char myInitials = ‘J’;  Page 55 Java OOP Programming 15

Math.pow(base, power) Math.sqrt(number) Java OOP Programming 16

Lesson 6 Project Java OOP Programming 17

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 Variables & Data Types  Data types and memory allocations (bytes)  Integer values  Output  Source code example of Integer arithmetic and output  Floating Point Data Types  Math  Pow  Sqrt  Other  Lesson 6: Blue Pelican Java Java OOP Programming 19

Java OOP Programming 20