Java Basics V3

www.SunilOS.com 1 JAVA BASICS www.sunilos.com www.raystec.com

www.SunilOS.com 2 Java is a Programming Language A programing language. Write computer programs Other programming language: o C/ C++ o Python o .Net o PHP etc.

What is programming? www.SunilOS.com 3 Video Game

Calculator / Bill Payment www.SunilOS.com 4

www.SunilOS.com 5 Basic elements of the Language 1. Command: an action 2. Variables/Attributes: memory to remember data 3. Data Type: number, decimal, character 4. Control Statement: conditional action 5. Functions/Methods: a task contains set of commands

www.SunilOS.com 6 Java is OOP 3 Idiot Java is Object Oriented Programming . follows OOP methodology. Java thinks only Objects.  Just like a Money Oriented Person who always thinks of Money. मेरी 4 लाख की घडी!! मेरी डेढ़ लाख की शेरवानी!! My 300$ shoes

www.SunilOS.com 7 Basic Unit of Java is Object Program of 1. Print Hello World is an object 2. Sum of two numbers is an object 3. Fibonacci Series is an object 4. SMS Service is an object 5. Email Service is an object 6. Account Service is an object Basic unit of Java is an Object. OOP is real world programming.

Class: structure of an object  What object will do? What are responsibilities of an object? What tasks are done by Object?  Class is the structure of an Object  Class defines Role and Responsibilities of an object  Ultimately a Program is a Class  When memory is allocated to class, it will become object www.SunilOS.com 8

Object Vs Class www.SunilOS.com 9 State/Variables • currentGear • speed • color Methods • changeGear() • accelerator() • break() State • name • address Methods • changeName() • earnMoney() Structure Real world entities

Object Vs Class www.SunilOS.com 10 State/Variables • balance • owner • type Methods • getBalance() • fundTransfer () • payBill() Real world entities

Class is the basic building block  The basic building block of Java is a Class.  Java program is nothing but a Class.  Java application is made of Classes. www.SunilOS.com 11

www.SunilOS.com 12 Class Class contains program elements Class contains methods and variables. Variables contain data Types of data are int, float, boolean, char and String. Methods perform operations.

Executable Class A Class is program A Class can be executed Executable Class must contain one method, names ‘main’ When you execute a class main() method is executed www.SunilOS.com 13

www.SunilOS.com 14 HelloWorld – First Java Program 1. public class HelloWorld { 2. public static void main(String[] args) { 3. System.out.println(“Hello World”); 4. } 5. } public, class, static, and void are keywords. Keywords are always written in small letters.

www.SunilOS.com 15 Pizza 1. public class Pizza { 2. public static void main(String[] args) { 3. int money = 99; 4. if (money > 100) { 5. System.out.println("Wow!!, I can buy Pizza :)"); 6. } else { 7. System.out.println("Oh!, I can not buy Pizza (:"); 8. } 9. } 10. }

Sum of Two Numbers public class Sum {  public static void main(String[] args) {  int a = 10;  int b = 5;  int c = a + b;  System.out.println(c);  } } www.SunilOS.com 16

Expert Class Each class is an Expert class An expert class contains related attributes and methods www.SunilOS.com 17 Doctor Advocate Engineer Astronaut

Specialization -Inheritance www.SunilOS.com 18 Doctor Heart Specialist ENT Specialist Cancer Specialist

Expert never overlaps other’s responsibilities www.SunilOS.com 19 Creator Preserver Destroyer Trimurti

Expert Classes www.SunilOS.com 20 :Automobile -color :String -speed:int -make:String +$NO_OF_GEARS +getColor():String +setColor() +getMake():String +setMake() +break() +changeGear() +accelerator() +getSpeed():int :Person -name:String -dob : Date -address:String +$AVG_AGE +getName():String +setName() +getAdress():String +setAddress() +getDob (): Date +setDob () +getAge() : int :Account -number:String -accountType : String -balance:double +getNumber():String +setNumber() +getAccountType():String +setAccountType() +deposit () +withdrawal () +getBalance():double +fundTransfer() +payBill()

Experts bring Modularity and Reusability www.SunilOS.com 21

www.SunilOS.com 22 Class Program Structure - Java int i = 5 //global variable void main(){ .. a(5); } void a(int k){ int j = 0; //local variable .. }

www.SunilOS.com 23 Package – group of related classes Package Class 1 Class 2 Class 3 Class 4

www.SunilOS.com 24 JAVA Application Application Package 1 Package 2 Package 3 Package 4  An application has multiple packages

Java Platform www.SunilOS.com 25 JDK JRE Development Kit javac.exe JVM (java.exe) JAVA Class Libraries AWT, I/O, Net etc.

Compile and Execute www.SunilOS.com 26 Hello.java (text) JVM (java.exe) Hello.class (bytecode) Compile (javac) • Compile .java file • c:>javac Hello.java • It will generate file Hello.class • Run the class by • c:>java Hello

Compile once run anywhere www.SunilOS.com 27 JVM Linux Hello.class (bytecode) JVM MacOS JVM Windows

www.SunilOS.com Control Statements if-else while for do-while GOTO 28

www.SunilOS.com While Loop  public class HelloWhile {  public static void main(String[] args) { o boolean जबतकहेजान = true; o int round = 0; o while (जबतकहेजान ) {  System.out.println(“मै बसंती नाचंगी !!!");  if(++round > 500 ) • जबतकहेजान = false; o }  }  } 30

www.SunilOS.com For Loop ₹10 for 5 shots How Much? Okay!! 31

 public class HelloFor {  public static void main(String[] args)  { o for (int shot=1; shot <= 5; shot++) o { o System.out.println(“Shot Balloon” + i); o } o }  } www.SunilOS.com For Loop – Five shots 32

www.SunilOS.com 33 Print Hello Java 5 times - for public class HelloFor { public static void main(String[] args) { o for (int i = 0; i < 5; i++) {  System.out.println("Hello Java "); o } o } }

www.SunilOS.com 34 Print Hello Java 5 times - while public class HelloWhile { public static void main(String[] args) { o int i = 0; o while (i < 5) {  System.out.println("Hello Java ");  i++; // i = i+1 o } } }

www.SunilOS.com 35 Print Hello Java 5 times – do-while public class HelloDoWhile { public static void main(String[] args) { int i = 0; o do {  System.out.println( i+ " Hello Java ");  i++; o } while (i < 5); } }

www.SunilOS.com 36 Foreach statement public class HelloFor { public static void main(String[] args) { o int[] table={ 2, 4, 6, 8, 10}; o for (int v : table) {  System.out.println(“Table “ + v); o } o } }

www.SunilOS.com 37 Add.java public class Add { public static void main(String[] args) { o int a = 5; o int b = 10; o int sum = a + b; o System.out.println("Sum is " + sum); } }

www.SunilOS.com 38 Java Primitive Data Types Primitive Data Types: o boolean true or false o char unicode (16 bits) o byte signed 8 bit integer o short signed 16 bit integer o int signed 32 bit integer o long signed 64 bit integer o float,double IEEE 754 floating point

www.SunilOS.com 39 java.lang.String class  String name = "Vijay Dinanath Chauhan";  S.o.p(" String Length- " + name.length());  S.o.p(" 7th character is- " + name.charAt(6));  S.o.p(" Dina index is- " + name.indexOf("Dina"));  S.o.p(" First i Position- " + name.indexOf("i"));  S.o.p(" Last i Position- " + name.lastIndexOf("i"));  S.o.p(" a is replaced by b- " + name.replace("a", "b"));  S.o.p(“ Chhota vijay- " + name.toLowerCase());  S.o.p(" Bada vijay- " + name.toUpperCase());  S.o.p(" Starts With Vijay- " + name.startsWith("Vijay"));  S.o.p(" Ends with han- " + name.endsWith("han"));  S.o.p(" Substring- " + name.substring(6));  Note : S.o.p = System.out.println

www.SunilOS.com 40 Java.lang.StringBuffer class  public static void main(String[] args) {  StringBuffer sb = new StringBuffer("Vijay");  sb.append(“ Dinanath Chauhan");  S.o.p("Length : " + sb.length());  S.o.p("Capacity :" + sb.capacity());  S.o.p("Char at :" + sb.charAt(1));  S.o.p("Index Of : " + sb.indexOf("Dinanth"));  S.o.p("Replace : " + sb.replace(0, 5, "Jay "));  S.o.p("Reverse : " + sb.reverse());

www.SunilOS.com 41 String vs StringBuffer String is immutable o Memory object can not be changed. StringBuffer is mutable o Memory object can be changed.

www.SunilOS.com 42 java.lang.Math class  public static void main(String[] args) { o S.o.p(“ Mathematics functions"); o S.o.p(" Max 2,5 - " + Math.max(2,5)); o S.o.p(" Min 2,5 - " + Math.min(2,5)); o S.o.p(" Absolute 3.7 - " + Math.abs(3.7)); o S.o.p(" Exp 10 - " + Math.exp(10)); o S.o.p(" Random Number- " + Math.random()); o S.o.p(" Square Root- " + Math.sqrt(4));  }  Note : S.o.p = System.out.println

www.SunilOS.com 43 Static vs Instance String name = “Vijay”; String surname = “Chauhan” S.o.p(name.length()); S.o.p(surname.length()); String.length() S.o.p(Math.max(2,5)); S.o.p(Math.max(5,10));

www.SunilOS.com 44 Other Data Types Reference types (composite) o objects o arrays strings are supported by a built-in class named String (java.lang.String). string literals are supported by JAVA as a special case.

www.SunilOS.com 45 Hello <Name>  public class HelloName { o public static void main(String[] args) { o System.out.println("Hello " + args[0]); o }  }  C:>java HelloName Vijay Dinanath Chauhan  class args[0] args[1] args[2]  C:>java HelloName “Vijay Dinanath” Chauhan

www.SunilOS.com 46 Hello Name – if <condition>  public class HelloName1 {  public static void main(String[] args) { o if (args.length == 1) {  System.out.println("Hello " + args[0]); o } else {  System.out.println(“Parameter name is required"); o }  }  }

www.SunilOS.com 47 Hello All public class HelloAll { public static void main(String[] args) { o for (int i = 0; i < args.length; i++) {  System.out.println(i + " = Hello " + args[i]); o } } }

www.SunilOS.com 48 Hello All (Cond)  public static void main(String[] args) {  int size = args.length;  if (size == 0) { o S.o.p("Usage : java HelloAll n1 n2 n3 .. ");  } else { o for (int i = 0; i < size; i++) { o S.o.p ( i+ " = Hello " + args[i]); o }  }  }

www.SunilOS.com 49 Hello All - switch  public static void main(String[] args) {  int size = args.length;  switch(size) {  case 0 :S.o.p("Usage : java HelloAll1 n1 n2 n3.."); o break;  case 1 : S.o.p(“Hello “ + args[0]); o break;  default : o for (int i = 0; i < size; i++) {  S.o.p(i + " = Hello " + args[i]); o }//for  }//switch  }//method

www.SunilOS.com 50 Add.java – Integer Arguments  public class Add {  public static void main(String[] args) { o int a = Integer.parseInt(args[0]); o int b = Integer.parseInt(args[1]); o int sum = a + b; o System.out.println("Sum is " + sum);  }  }  C:>java Add 10 20

www.SunilOS.com 51 Division  public class Division { o public static void main(String[] args) { o int a = Integer.parseInt(args[0]); o int b = Integer.parseInt(args[1]); o double div = a/b; o System.out.println("Division is " + div); o }  }

www.SunilOS.com 52 Define a Method  public static void main(String[] args) { o printAll(args);  }// main  public static void printAll(String[] args) { o for (int i = 0; i < args.length; i++) {  System.out.println(“Hello " + args[i]); o }  }//printAll

www.SunilOS.com 53 Return a Value  public static double getDivision(int a, int b) o {  double div = a / b;  return div; o }  }

www.SunilOS.com 54 Command line Menu  public static void main(String[] args) throws Exception{  int ch = System.in.read(); //Read data from keyboard  System.out.println( "Selected char ASCII Code " + ch);  if (ch == 'A' || ch == 'a') {  Add.main(args); o } else if (ch == 'D' || ch == 'd') {  Division.main(args); o } else {  S.o.p("Incorrect Choice "); o } o }  }

www.SunilOS.com 55 10 One Dimension Array 20 [0] 18 .. 10 8 6 4 2 [1] [8] [9] [2] [3] [4] [n] length int[] table = new int[10]; int a = table[4]; int a = table[2]; int size = table.length;

www.SunilOS.com 56 10 Initialize an Array 20 [0] 18 .. 10 8 6 4 2 [1] [8] [9] [2] [3] [4] [n] length int[] table = new int[10]; table[0] =2; table[1] =4; …. Or int[] table = {2,4,6,8,10,12,14,16,18,20};

www.SunilOS.com 57 Other Data Type Arrays char[] chList = new char[5]; chList[0] = ‘A’…. o Or char[] chList = {‘A’,’B’,’C’,’D’,’E’} String[] strList = new String[5]; strList[0] = “A” strList[1] = “Bee” o Or String[] strList = {“A”,”Bee”,”Cee”,”Dee”,”E”}

www.SunilOS.com 58 Copy an Array public static void main(String[] args) { o char[] copyFrom = { 'd', 'e', 'c', 'a', 'f', 'f', 'e', 'i', 'n', 'a', 't', 'e', 'd' }; o char[] copyTo = new char[7]; o System.arraycopy(copyFrom, 2, o copyTo, 0, 7); o S.o.p(new String(copyTo)); } Start Index Start Index No Of Element

www.SunilOS.com 59 One Dimension Array int[] table; table = new int[10]; table[0] =2; table[1] =4; 4B 10 [0] [1] [9] length 2 4 20 1000 1000 table

www.SunilOS.com 60 10 length 2D Array [0] 20 18 .. 10 8 6 4 2 [1] [8] [9] [2] [3] [4] [n] 30 27 .. 15 12 9 6 3 40 36 .. 20 16 12 8 4 90 81 .. 45 36 27 18 9 100 90 .. 50 40 30 20 10 … [0] [1] [2] [7] [8] 9 9 .. 9 9 9 9 9

www.SunilOS.com 61 int[][] table = new int[10][9]; table 1010 1000 1000 1011 1111 1010 1011 1111

www.SunilOS.com 62 Define an Array  int[][] table = new int[10][9];  table[1][5] = 5;  int size = table.length;  int size = table[0].length;  int[][] rows = new int[10][];  rows[0] = new int[9];  rows[1] = new int[19];  rows[2] = new int[29];  int[][][] xyz = new int[10][9][2];

www.SunilOS.com 63 3D Array 20 [0] 18 .. 10 8 6 4 2 [1] [8] [9] [2] [3] [4] [n] 30 27 .. 15 12 9 6 3 40 36 .. 20 16 12 8 4 90 81 .. 45 36 27 18 9 100 90 .. 50 40 30 20 10 [0] [1] [2] [8] [9] 20 18 .. 10 8 6 4 2 30 27 .. 15 12 9 6 3 40 36 .. 20 16 12 8 4 20 18 .. 10 8 6 4 30 27 .. 15 12 9 6 20 18 .. 10 8 6 4 2 30 27 .. 15 12 9 6 3 40 36 .. 20 16 12 8 4 90 81 .. 45 36 27 18 9 100 90 .. 50 40 30 20 10 90 81 .. 45 36 27 18 9 100 90 .. 50 40 30 20 10 … [0] [1] [2]

www.SunilOS.com 64 java.util.Date class  import java.util.*;  public class TestDate {  public static void main(String[] args) { o Date d = new Date(); o S.o.p("Date : " +d); o S.o.p ("Long Time : " +d.getTime());  }  Output o Date : Mon Jan 04 00:35:53 IST 2010 o Long Time : 1262545553156

www.SunilOS.com 65 Format a Date  import java.util.*; import java.text.SimpleDateFormat;  public class TestDateFormat{  public static void main(String[] args) { o Date d = new Date(); o SimpleDateFormat format= new SimpleDateFormat("dd/MM/yyyy"); o String str = format.format(d); o S.o.p("Date : " + str ); o String str1 = "22/03/2009"; o Date d1 = format.parse(str1); o S.o.p(d1);  }  Output o String : 04/01/2010 o Sun Mar 22 00:00:00 IST 2009

Disclaimer This is an educational presentation to enhance the skill of computer science students. This presentation is available for free to computer science students. Some internet images from different URLs are used in this presentation to simplify technical examples and correlate examples with the real world. We are grateful to owners of these URLs and pictures. www.SunilOS.com 66

Thank You! www.SunilOS.com 67 www.SunilOS.com

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