IntroductionToProgramming PDF

CSE 114, Computer Science 1Stony Brook University

http://www.cs.stonybrook.edu/~cse114

Introduction to Computers, Programs, and Java

(c) Pearson Education, Inc. & Paul Fodor (CS Stony Brook)

What do you need to get started? Blackboard account

http://blackboard.stonybrook.edu SINC Sites: http://www.sinc.sunysb.edu/helpdesk/labs.shtml Java:

http://java.com/en/download/index.jsp Eclipse IDE:

http://www.eclipse.org/downloads Learn to use the debugger

Liangs student Web site: http://www.cs.armstrong.edu/liang/intro9e

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How does it work? Java Source Code

you write this ProgramName.java files

Compiler Program Build - included in the Eclipse IDE

OR Command: javac ProgramName.java

results Java Executable Code ProgramName.class files - not humanly readable

Java Virtual Machine runs Java programs Run - included in the Eclipse IDE

OR command: java ProgramName3


What is a Computer?

4

A computer consists of a CPU, memory, hard disk, monitor, printer, and communication devices.

CPU

e.g., Disk, CD, and Tape

Input Devices

e.g., Keyboard, Mouse

e.g., Monitor, Printer

Communication Devices

e.g., Modem, and NIC

Storage Devices

Memory

Output Devices

Bus


CPU

5

CPU


Input Devices





Storage Devices

Memory

Output Devices

Bus

central processing unit (CPU)

retrieves instructions from memory and executes them

the CPU speed is measured in megahertz (MHz)

1 megahertz = 1 million pulses per second


Memory

6

CPU


Input Devices





Storage Devices

Memory

Output Devices

Bus

stores data and program instructions for CPU to execute

ordered sequence of bytes (8 bits binary base unit)


How Data is Stored?

7

Whats binary? a base-2 number system

What do humans use? base-10 Why?

Why do computers like binary? electronics easier to make hardware that

stores and processes binary numbers than decimal numbers

more efficient: space & cost

.

.

. 2000 2001 2002 2003 2004

.

.

. 01001010 01100001 01110110 01100001 00000011

Memory contentMemory address

Encoding for character J

Encoding for character a Encoding for character v

Encoding for character a Encoding for number 3

(c) Pearson Education, Inc. & Paul Fodor (CS Stony Brook)8

Number Systems

0, 1

0, 1, 2, 3, 4, 5, 6, 7

0, 1, 2, 3, 4, 5, 6, 7, 8, 9

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F

binary

octal

decimal

hexdecimal


Computers use binary numbers internally because storage devices like memory and disk are made to store 0s and 1s.

A number or a text inside a computer is stored as a sequence of 0s and 1s. Each 0 and 1 is called a bit (short for binary digit)

Binary numbers are not intuitive, since we use decimal numbers in our daily life.

When you write a number like 20 in a program, it is assumed to be a decimal number.

Internally, computer software is used to convert decimal numbers into binary numbers, and vice versa.

Number Systems


The digits in the decimal number system are 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. A decimal number is represented using a sequence of one or more of these digits. The value that each digit in the sequence represents depends on its position. A position in a sequence has a value that is an integral power of 10. e.g., the digits 7, 4, 2, and 3 in decimal number 7423 represent 7000, 400, 20, and 3, respectively:

We say that 10 is the base or radix of the decimal number system. The base of the binary number system is 2 since the binary number system has two digits The base of the hex number system is 16 since the hex number system has sixteen digits.

1037 4 2 3

102 101 100

0123 103102104107 +++=

3204007000 +++= 7423=

Number Systems


Binary numbers tend to be very long and cumbersome: For example: 101010101010

Hexadecimal numbers are often used to abbreviate binary numbers: For example: AAA

The hexadecimal number system has 16 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F.

The letters A, B, C, D, E, and F correspond to the decimal numbers 10, 11, 12, 13, 14, and 15.

Number Systems


Binary Numbers => Decimals

Given a binary numberthe equivalent decimal value is

10 in binary = 2 in decimal

1010 in binary = 10 in decimal

01221 ... bbbbbb nnn

01221 222...222 01221 ++++++ bbbbbb nnn nnn

021 1 +

0212021 23 +++

10101011 in binary

= 171 in decimal

121202120212021 234567 +++++++


Decimals => Binary To convert a decimal number d to a binary number is to find the binary digits.. such that

These numbers can be found by successively dividing d by 2 until the quotient is 0. The remainders are

For example, the decimal number 123 is 1111011 in binary. The conversion is conducted as follows:

01221 ,,,...,,, bbbbbb nnn

01221 222...222 01221 ++++++= bbbbbbd nnn nnn

01221 ,,,...,,, bbbbbb nnn

1232

61

122 1

b0

612

30

60 1

b1

302

15

30 0

b2

152

7

14 1

b3

Remainder

Quotient

72

3

6 1

b4

3 2

1

2 1

b5

1 2

0

0 1

b6


Windows CalculatorThe Windows Calculator is a useful tool for performing number conversions. To run it, choose Programs, Accessories, and Calculator from the Start button.


Hexadecimals => Decimals

The hexadecimal number system has sixteen digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F. The letters A, B, C, D, E, and F correspond to the decimal numbers 10, 11, 12, 13, 14, and 15. Given a hexadecimal numberThe equivalent decimal value is

01221 161616...161616 01221 ++++++ hhhhhh nnn nnn

7F in hex 15167 1 + = 127 in decimal

FFFF in hex = 65535 in decimal15161516151615 23 +++

01221 ... hhhhhh nnn


To convert a decimal number d to a hexadecimal number is to find the hexadecimal digits such that

01221 161616...161616 01221 ++++++= hhhhhhd nnn nnn

These numbers can be found by successively dividing d by 16 until the quotient is 0. The remainders are

For example, the decimal number 123 is 7B in hexadecimal. The conversion is conducted as follows:

01221 ,,,...,,, hhhhhh nnn

nnn hhhhhh ,,,...,,, 12210

12316

7

112 11

h0

7 16

0

0 7

h1

Remainder

Quotient

Decimals => Hexadecimals


0000 0 00001 1 10010 2 20011 3 30100 4 40101 5 50110 6 60111 7 71000 8 8 1001 9 91010 A 101011 B 111100 C 121101 D 131110 E 141111 F 15

Binary Hex Decimal To convert a hexadecimal number to a binary number, simply convert each digit in the hexadecimal number into a four-digit binary number.

To convert a binary number to a hexadecimal, convert every four binary digits from right to left in the binary number into a hexadecimal number. For example,

1 1 1 0 0 0 1 1 0 1

D83

Hexadecimals Binary


Memory: What goes in each memory segment?

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Stack Segment temporary variables declared inside methods removed from memory when a method returns

Heap Segment for dynamic data (whenever you use new) data for constructed objects persistent as long as an existing object variable

references this region of memory

Global Segment data that can be reserved at compile time global data (like static data)


How objects are stored?You must understand that in Java, every

object/reference variable stores a memory address32 bit numbers (4 bytes)

These addresses point to memory locations where the objects data is stored

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So Hardware stores 0s & 1s

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0101010101010101010101010101 Data is byte addressablewe can access or change any byte (group of 8 bits)

independently as neededHow do we store text?Numerically (using its code)Each character is stored in memory as a numberStandard character sets: ASCII & UnicodeASCII uses 1 byte per character A is 65


Programming Languages

22

Machine Language Assembly Language High-Level Language

A program called assembler is used to convert assembly language programs into machine codeFor example, to add two numbers, you might write an instruction in assembly code like this:

ADDF3 R1, R2, R3

ADDF3 R1, R2, R3

Assembly Source File

Assembler

1101101010011010

Machine Code File


Programming Languages

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Machine Language Assembly Language High-Level Language

assembly: Far easier to use than binaryBUT: not very user friendly, very low-level operations, programming is time consuming

High Level programming Languages (HLL): more user friendly, easy to use more flexible platform independent


Popular High-Level Languages

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COBOL (COmmon Business Oriented Language)FORTRAN (FORmula TRANslation) BASIC (Beginner All-purpose Symbolic Instructional Code) Pascal (named for Blaise Pascal) Ada (named for Ada Lovelace) C (whose developer designed B first)Visual Basic (Basic-like visual language developed by Microsoft) Delphi (Pascal-like visual language developed by Borland) C++ (an object-oriented language, based on C)C# (a Java-like language developed by Microsoft)Java


Compiling Source Code

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Whats a compiler? A software program Input: High Level Language source codeOutput: Assembly Code

It is typically integrated with an assembly together they can make an executable or binary program

Compiler Source File Machine-language

File Linker Executable File

Library Code


Operating Systems

26

The operating system (OS) is a program that manages and controls a computers activities

Windows XP, Vista, 7 and 8

Mac OsXAndroidLinux

User

Application Programs

Operating System

Hardware


Why Java?

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Java is somewhat differentJava has a principle, write once, run anywhere

What does that mean?Platform independence for compiled Java code

How?The Java Virtual Machine

Java programs are compiled into Java bytecodebytecode is executed by the

Java Virtual Machine (JVM)


Java, JVM, Web, and Beyond

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Java Virtual MachineA program that runs Java programs and manages

memory for Java programs. Why?Each platform is different (Mac/PC/Linux/etc.) Java can be used to develop Web applications. Java Applets Java Web Applications Java can also be used to develop applications for hand-

held devices such as Palm and cell phones


JDK Versions

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JDK 1.02 (1995) JDK 1.1 (1996) JDK 1.2 (1998) JDK 1.3 (2000) JDK 1.4 (2002) JDK 1.5 (2004) a. k. a. JDK 5 or Java 5 JDK 1.6 (2006) a. k. a. JDK 6 or Java 6 JDK 1.7 (2011) a. k. a. JDK 7 or Java 7 JDK 1.8 (2014) a. k. a. JDK 8 or Java 8


JDK Editions

30

Java Standard Edition (J2SE) J2SE can be used to develop client-side standalone

applications or applets. Java Enterprise Edition (J2EE)

J2EE can be used to develop server-side applications such as Java servlets and Java ServerPages.

Java Micro Edition (J2ME). J2ME can be used to develop applications for mobile devices

such as cell phones. Our textbook uses J2SE to introduce Java

programming.


A Simple Java Program

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//This program prints Welcome to Java! public class Welcome {

public static void main(String[] args) { System.out.println("Welcome to Java!");

}}


Creating, Compiling, and Running Programs

32

Source Code

Create/Modify Source Code

Compile Source Code i.e., javac Welcome.java

Bytecode

Run Byteode i.e., java Welcome

Result

If compilation errors

If runtime errors or incorrect result

public class Welcome { public static void main(String[] args) { System.out.println("Welcome to Java!"); } }

Method Welcome() 0 aload_0 Method void main(java.lang.String[]) 0 getstatic #2 3 ldc #3 5 invokevirtual #4

8 return

Saved on the disk

stored on the disk

Source code (developed by the programmer)

Byte code (generated by the compiler for JVM to read and interpret, not for you to understand)


pfodor@sparky ~$ pico Welcome.java



}}

pfodor@sparky ~$ javac Welcome.java

pfodor@sparky ~$ java Welcome Welcome to Java!

Running Programs from command line


Compiling and Running Java from the Command Window

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Set path to JDK bin directory set path=c:\Program Files\Java\jdk1.8.0\bin check Java path

Set classpath to include the current directory set classpath=.

Compile javacWelcome.java

Run java Welcome


Running Programs in Eclipse


Supplements on the Companion Website

36

See Supplement I.B for installing and configuring JDK

See Supplement I.C for compiling and running Java from the command window for details

See Supplement II.D for installing and using Eclipse IDE

http://www.cs.armstrong.edu/liang/intro10e


Trace a Program Execution

37



}}

Enter main method




}}

Execute statement





}}

print a message to the console



Anatomy of a Java Program

40

CommentsReserved wordsModifiers Statements BlocksClassesMethodsThe main method


Comments

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Line comment: A line comment is preceded by two slashes (//) in a line.Paragraph comment: A paragraph comment is enclosed between /* and */ in one or multiple lines.

javadoc comment: javadoc comments begin with /** and end with */. They are used for documenting classes, data, and methods. They can be extracted into an HTML file using JDK's javadoc command.

Three types of comments in Java.


Reserved Words

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Reserved words or keywords are words that have a specific meaning to the compiler Cannot be used for other purposes in the program Example: class

the word after class is the name for the class


Java Vocabulary Words (Keywords)abstract,assert,boolean,break,byte, case,catch,char,class,const,continue,default,do,double,else,enum,extends,false,final,finally,float,for,goto,if,implements,import,instanceof,int,interface,long,native,new,null, package,private,protected,public, return,short,static,strictfp,super, switch,synchronized,this,throw, throws,transient,true,try,void, volatile,while

http://docs.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html43


Modifiers

44

Java uses certain reserved words called modifiers that specify the properties of the data, methods, and classes and how they can be used Examples: public, static, private, final, abstract, protectedA public datum, method, or class can be accessed by other programsA private datum or method cannot be accessed by other programs


Statements

45

A statement represents an action or a sequence of actions

System.out.println("Welcome to Java!");is a statement to display the greeting "Welcome to Java!"

Every statement in Java ends with a semicolon (;)


A pair of braces in a program forms a block that groups components of a program.

public class Test { public static void main(String[] args) { System.out.println("Welcome to Java!"); } }

Class block

Method block

Blocks


Variable, class, and method names Whats an API?

Application Programming Interface a library of code to use

Names (variables, classes, and methods) From 2 sources:

your own classes, variables, and methods the Oracle/Sun (or someone elses) API

Your Identifiers (Names) Why name them? they are your data and commands youll need to reference them elsewhere in your programint myVariable = 5; // Declaration... // Using the variablemyVariable = myVariable + 1;

47


Rules for Identifiers Should contain only letters, numbers, & _ Cannot begin with a digit Uppercase and lowercase letters are considered to be

different characters $ is allowed, but only for special use. Examples: Legal: myVariable, my_class, my4Var Illegal: 4myVariable, my class, my!Var, @#$myClass

48


Common Java Naming Conventions Variables & Methods start with lower case letters: x, toString

Classes start with upper case letters: Person Variables and Class identifiers should generally be nouns Method identifiers should be verbs Use Camel notation: myVariable, MyClass Although it is legal, do not begin with _ (underscore). Use descriptive names: LinkedList, compareToarea = PI * radius * radius;49


Variables In a program, they store data Primitives store single pieces of data (ex: char)char letter = 'A';

Objects store multiple pieces of data (ex: String)String text = "ABCDEFG";

All Java variables must have a declared type A variables type determines:what kind of value the variable can holdhow much memory to reserve for that variable

50


Javas Primitive Types Integers (whole numbers)

byte1 byte (-128 to 127) short 2 bytes (-32768 to 32767) int4 bytes (-2147483648 to 2147483647) long8 bytes (-9223372036854775808 to

9223372036854775807) Real Numbers

float4 bytes double8 bytes

char2 bytes stores a single character (Unicode 2)

booleanstores true or false (uses 1-bit or byte)51


Variables Must be declared before being assigned valuespublic void methodWithGoodDeclaration(){double salary;salary = 20000.0;System.out.println("Salary is " + salary);

}public void methodWithBadDeclaration(){salary = 20000.0;double salary;System.out.println("Salary is " + salary);

}52


Variables Must be initialized before being referencedpublic void methodWithGoodReference(){double salary;salary = 20000.0;double raise = salary * 0.05; // 5% raiseSystem.out.println("Raise is " + raise);

}

public void methodWithBadReference(){double salary; // Salary has no value.double raise = salary * 0.05;System.out.println("Raise is " + raise);

}53


Variables A variable gets a value in an assignment statement (discussed

later).Variable = some_value or

an expression Undefined Variables

Compiler error If a variable does not occur on the left in an assignment

statement before its use in an expression, then it is probably undefined

54


Variables Should only be declared oncepublic void methodWithGoodDeclaration(){double salary = 20000.0;System.out.println("Salary is " + salary);salary = 60000.0;System.out.println("Salary is " + salary);

}

public void methodWithBadDeclaration(){double salary = 50000.0;System.out.println("Salary is " + salary);double salary = 60000.0; // Second declarationSystem.out.println("Salary is " + salary);

}55


Variables Variables can be declared and initialized at once

char yesChar = 'y';String word = "Hello!";double avg = 0.0, stdDev = 0.0;char initial3 = 'T'; boolean completed = false;

56


Variables Variables can only be used inside the block { } or

scope that they themselves are declaredpublic void methodWithGoodScope(){double x = 5.0;if (x > 0.0)

System.out.println("x is " + x);} // x is in scope here.public void methodWithBadScope(){double y = 100.0;if (y > 0.0) {

double x = 5.0;}System.out.println("x " + x); // x is not in scope

}57


Variables The Assignment Statementvariable = expression;

What does it do? Solves/evaluates expression first Assigns resulting value to the variable

Exercise: Whats the output?int x = 5;x = x + x + x + 10;System.out.print(x); ?

58


Variables The Assignment Statementvariable = expression;

What does it do? Solves/evaluates expression first Assigns resulting value to the variable

Exercise: Whats the output?int x = 5;x = x + x + x + 10;System.out.print(x); 25

59


Variables Assignment Compatibility: The variable and expression should be the same type if not, you may get a compiler error.

Examples: int sumGrades, gradeX, gradeY;gradeX = 1;sumGrades = 1473;sumGrades = 1472 + 1;sumGrades = 1472 + gradeX;sumGrades = true; // ILLEGAL

60


Variables What about mixing numeric types? Are these assignment statements ok?int x = 5;long y = x;double z = y;

What about these?double a = 6.5;long b = a;int c = b;

byte


Variables Type Casting as a type override

temporarily change a data type to another type (type_name), example: (int) no type casting to/from boolean Examples: double myReal = 10.0;int badInt = myReal;int goodInt = (int)myReal;

62


Arithmetic Operators+ Addition- Subtraction* Multiplication/ Division% Modulo/Remainder (integer operands only)

int x = 5;int y = 10;int z = 2;int num1 = (x + y) * z;System.out.println(num1); ?

63


Arithmetic Operators+ Addition- Subtraction* Multiplication/ Division% Modulo/Remainder (integer operands only)

int x = 5;int y = 10;int z = 2;int num1 = (x + y) * z;System.out.println(num1); 30

64


Arithmetic Operators Multiplication (*) has higher precedence over addition (+). int x = 5;int y = 10;int z = 2;int num1 = x + y * z;System.out.println(num1); ?

Whenever in doubt, go with explicit use of parentheses. My Advice: avoid rules of precedenceint r2d2c3po = 3 * 4 + 5 / 6; // ?int r2d2c3po2 = (3 * (4 + 5))/ 6; // ?

65


Arithmetic Operators Multiplication (*) has higher precedence over addition (+). int x = 5;int y = 10;int z = 2;int num1 = x + y * z;System.out.println(num1); 25

Whenever in doubt, go with explicit use of parentheses. My Advice: avoid rules of precedenceint r2d2c3po = 3 * 4 + 5 / 6; //12int r2d2c3po2 = (3 * (4 + 5))/ 6; //4

66


Division Integer division:

8/3 = 2 Double division:

8.0/3.0 = 2.666666666666667 8.0/3 = 2.666666666666667 8/3.0 = 2.666666666666667

67


Arithmetic Operators Division Operator - evaluate full expression firstdouble average = 100.0/8.0; //12.5average = 100.0/8; //12.5average = 100/8; //12.0int sumGrades = 100/8; //12sumGrades = 100.0/8.0; //ERRORsumGrades = (int)100.0/8.0; //ERRORsumGrades = (int)(100.0/8.0); //12int fifty_percent = 50/100; //0double fiftyPercent = 50/100; //0.0fiftyPercent = 50.0/100.0; //0.5

68


Arithmetic Operators The modulo/remainder % operator

Produces division remainders

int remainder = 100 % 8; System.out.println(remainder); ?

69


Arithmetic Operators The modulo/remainder % operator

Produces division remainders

int remainder = 100 % 8; System.out.println(remainder); 4

70


Arithmetic Operators++ Increment by one-- Decrement by one+= Increment by specified amount-= Decrement by specified amount*= Multiply by specified amount/= Divide by specified amountint x = 5, y = 15, z = 25;x = x + 1;y++;

z += 1;System.out.println(x); ?System.out.println(y); ?System.out.println(z); ?71



z += 1;System.out.println(x); 6System.out.println(y); ?System.out.println(z); ?72



z += 1;System.out.println(x); 6System.out.println(y); 16System.out.println(z); ?73



z += 1;System.out.println(x); 6System.out.println(y); 16System.out.println(z); 2674


Increment andDecrement Operators, cont.

75

int i = 10; int newNum = 10 * i++; int newNum = 10 * i;

i = i + 1;

Same effect as

int i = 10; int newNum = 10 * (++i); i = i + 1;

int newNum = 10 * i;

Same effect as


Scientific Notation Floating-point literals can also be specified in scientific

notation: E (or e) represents an exponent and it can be either in

lowercase or uppercase

Examples1.23456e+2 = 1.23456e2 = 123.4561.23456e-2 = 0.0123456

76


Classes

77

A class is a template or blueprint for objectsA program is defined by using one or more classespublic class ClassName {

public static void main(String[] args) {// ClassName PROGRAMS POINT OF ENTRY// THIS PROGRAMS INSTRUCTIONS// START HERE

}}


Methods

78

A method is a collection of statements that performs a sequence of operations

It is used by invoking a statement with arguments

System.out.println("Welcome to Java!");


main Method

79

The main method provides the control of program flow. ClassName is executable because it has a main method

we can compile and then run it Not all classes require main methods

only those classes that initiate program execution require a main method

public class ClassName {public static void main(String[] args) {

...

}}


Our first program: HelloWorldApp.java/*** HelloWorldApp is a Java application* that simply displays "Hello World! in the* Java console.*/public class HelloWorldApp {public static void main(String[] args) {

System.out.println("Hello World!");// Statement above displays "Hello World!"

}}

80


Homework 1

Homework 1 won't be not gradedLearn submission of homework

through Blackboard as an assignment

81


> notepad Welcome.java



}}

> javac Welcome.java

> java Welcome Welcome to Java!

Homework: Implement&TestWelcome.java

82


import java.util.Scanner;

public class ChangeMaker {public static void main(String[] args) {

int change, rem, qs, ds, ns, ps;System.out.print("Input change amount (1-99): ");Scanner input = new Scanner(System.in);change = input.nextInt();qs = change / 25;rem = change % 25;ds = rem / 10;rem = rem % 10;ns = rem / 5;rem = rem % 5;ps = rem;

System.out.print(qs + " quarters," + ds + " dimes,");System.out.println(ns + " nickels and" + ps + " pennies");

} }

Homework: Implement ChangeMaker

Eclipse

83

IntroductionToProgramming PDF

Documents

printer communication

paul fodor cs stony

tape input devices

javac pearson education

binary digit binary

secondc pearson education

decimal numbers

processes binary numbers