Introduction to programming in java

Input and output to screen with Java program Structure of Java programs Statements Conditional statements Loop constructs Arrays, character and string handling Functions Syllabus

Structure of Java programs Input and output to screen with Java program Statements (what is a statement) Lecture Outcomes

Books & References Introduction to Java and Object Oriented Programming (Volume 1) 1.Chapter 2. After todays Lecture you should be able to complete all exercises In Section 2.10, page Chapter 3 If you are confident with all the material in Chapter 2, then start Reading Chapter 3. 3.Extra More practise exercises are on page:

Structure of Java programs Compiling and running the program Printing messages to the screen Contents for Todays Lecture

Some Basics Definition of a program? A sequence of instructions that a computer can interpret and execute. Why dont we just use natural languages such as English? A computer is not intelligent enough to understand natural languages.

class class-name { public static void main(String args[]) { statement1; statement2; … } Structure of Java Programs class-name.java

8 A statement written in Java println(Hello World!"); String hello = Hello World!"; println(hello); every statement is terminated with a ;

First.java Public class First { public static void main(String args[]) { System.out.println(Hello World); } Example Program statement

10 Creating and Compiling Programs On command line – javac file.java

11 Executing Applications On command line – java classname

12 Example javac Welcome.java java Welcome output:...

Compile and run java command line Compile javac file-name.java Run java filename Compile javac HelloWorld.java Runjava HelloWorld Example: HelloWorld.java

Compiling: is the process of translating source code written in a particular programming language into computer-readable machine code that can be executed. $ javac First.java This command will produce a file First.class, which is used for running the program with the command java. Running: is the process of executing program on a computer. $ java First Compiling & Running the Program

second.java class second { public static void main(String args[]) { System.out.println(Hello World); } Example Program Compile javac second.java Run java second

HelloWorld.java class HelloWorld{ public static void main(String args[]) { System.out.println(Hello World); } Example Program Compile javac HelloWorld.java Runjava HelloWorld

1.HelloWorld java 2.Welcome.java 3.Myname.java 4.MyDate ofBirth.java Compile Run a few example using Command line

1.System.out.println(Hello World); – outputs the string Hello World followed by a new line on the screen. 2.System.out.print(Hello World); - outputs the string Hello World on the screen. This string is not followed by a new line. 3.Some Escape Sequence – \n – stands for new line character \t – stands for tab character About Printing on the Screen

19 Java print() and println() Text can be printed on the screen using print() or println(). Using println() puts a new line at the end of the text. print("7*3"); println("="); println(7*3); This code prints: 7*3= 21

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

Example Welcome3.java ( includes \n and \t) public class Welcome { public static void main(String args[]) { System.out.print("Welcome \n "); System.out.print("to \t"); System.out.println(java!"); } Welcome to java! Output

Some common errors in the initial phase of learning programming: - Mismatch of parentheses - Missing ; at the end of statement - Case sensitivity Writing programs on your own is the best way to learn how to program. Some Tips About Programming

23 Comments in java There are two ways of commenting code. Comments starting with // and terminated by end of line // Lahcen Ouarbya // 1 October 2012 // Hello World Comments enclosed in /* */ /* Lahcen Ouarbya 1 October 2012 Hello World */ good to make several lines of comments stand out in your program

24 Concatenating output with + print("I like programming in "); println("Java"); This code prints: I like programming in Java print("I like programming in + Java ); This code prints: I like programming in Java println( square root of 4 = " 2 + " or " -2); This code prints: square root of 4 = 2 or -2

Example Concatenate.java public class Concatenate { public static void main(String args[]) { System.out.print("I like programming in "); System.out.println(java"); System.out.println("I like programming in + java); System.out.println( square root of 4 = " or + -2); } { } I like programming in java square root of 4 = 2 or -2 Output

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

1.Write a program which prints the following information about at least 5 persons: `Full Name ` -Address ` Telephone Number use print and println and see the difference. 2.Write a program that prints the time table of 5 and time table of 9. (you will need to use concatenation.) Some Assignments

End Using Command line Arguments public class TestMain { public static void main(String args[]) {... } java TestMain arg0 arg1 arg2 … argn }

Processing Command-Line Parameters The main method, get the arguments from args[0], args[1],..., args[n] arg0, arg1,..., argn }

Example Argument.java public class Welcome { public static void main(String args[]) { System.out.print("Hi, "); System.out.print(args[0] + " " ); System.out.println(". How are you?"); } Hi, Lahcen. How are you? Java Argument Lahcen

Example Argument1.java public class Argument1 { public static void main(String args[]) { System.out.print("Hi, "); System.out.print(args[0] + " " ); System.out.print(args[1] + " " ); System.out.println(". How are you?"); } Hi, java programs. How are you? Java Argument java programs

Example Argument2.java public class Argument2 { public static void main(String args[]) { System.out.print("Hi, + args[0] + args[1] + (". How are you?"); } Hi, java programs. How are you? Java Argument java programs

summary HelloWorld.java Compile and run java programms. print/println \n new line \t tab Concatenation Use of Arguments.

More practice exercises. Introduction to Java and Object Oriented Programming (Volume 1) 1.Chapter 2. After todays Lecture you should be able to complete all exercises In Section 2.10, page Chapter 3 If you are confident with all the material in Chapter 2, then start Reading Chapter 3. 3.Extra More practise exercises are on page: