Slide 1 of 40. Lecture A The Java Programming Language Invented 1995 by James Gosling at Sun Microsystems. Based on previous languages: C, C++, Objective-C, … Intended to be a safe programming language for the Internet Common choice for first programming language  Object oriented  Encourages good programming habits  Very popular commercially  Simpler and more elegant than C++, but similar to it  Cool

Slide 2 of 40. Lecture A Hello World Program // My First Program!! public class HelloWorld { public static void main(String[] args){ System.out.println(“Hello World!”); }

Slide 3 of 40. Lecture A Java Program Elements Words  Keywords  Identifiers Constants  Numbers  Strings Symbols  ( ) [ ] { },. ; + - * / Comments

Slide 4 of 40. Lecture A Java Elements // My First Program!! public class HelloWorld { public static void main(String[] args){ System.out.println(“Hello World!”); } Comment Identifier Symbols Keywords String Constant

Slide 5 of 40. Lecture A Java Program Structure A program is composed of a collection of classes Each class contains a collection of methods Each method is composed of a sequence of instructions (commands, statements)

Slide 6 of 40. Lecture A Java Program Structure // My First Program!! public class HelloWorld { public static void main(String[] args){ System.out.println(“Hello World!”); } Class Method Instruction

Slide 7 of 40. Lecture A Running a Java Program Use an editor to enter (type) the program  Save to a file named HelloWorld.java Use the compiler to translate the program into bytecode  javac HelloWorld.java  This produces a file named HelloWorld.class Run the program using the Interpreter  java HelloWorld

Slide 8 of 40. Lecture A Java Compilation Compiler Xxx.java Xxx.class Interpreter Output

Slide 9 of 40. Lecture A Entering a Java Program into an Editor

Slide 10 of 40. Lecture A Running a Java Program