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Air Force Institute of Technology Electrical and Computer Engineering Object-Oriented Programming Design Topic 1: The Java Environment Maj Joel Young [email protected] 30-Apr-17 Maj Joel Young Object-Oriented Programming Design The Java Environment • Java code is compiled to an intermediate form called “bytecode” • The bytecode is executed by a simulated computer called the Java Virtual Machine (JVM) • The JVM translates bytecode instructions to your machine Java Code Java Compiler Byte Code JVM CPU 30-Apr-17 Air Force Institute of Technology Electrical and Computer Engineering 2 Object-Oriented Programming Design The Java Environment • Java maintains its portability by keeping the bytecode the same across all platforms • The JVM specification is open so that vendors can write one for their platforms • JVMs available from Sun, IBM, Microsoft, and others Byte Code JVM CPU 30-Apr-17 Air Force Institute of Technology Electrical and Computer Engineering 3 Object-Oriented Programming Design Java Programming Environment • Sun Microsystems Java Development Kit (JDK) – – – – Available at www.java.sun.com Latest version is JDK 1.4.2 Sun refers to all releases after 1.1.8 as “Java 2” Contains compiler, JVM, and tools • Java API Docs: http://java.sun.com/j2se/1.3/docs/api/ • Integrated Development Environments – Features include specialized editors, debuggers, GUI builders … but be comfortable with command line first – Recommended – get up to speed fast – Eclipse – IBM – http://www.eclipse.org/ (JDK 1.3), libre – DrJava – http://www.drjava.org/, can interface with Eclipse, libre – TogetherSoft – R:\Simulations\TogetherSoft (Academic Version) – JBuilder – www.inprise.com/jbuilder (free version) 30-Apr-17 Air Force Institute of Technology Electrical and Computer Engineering 4 Object-Oriented Programming Design Example Java Program class HelloWorld { static public void main(String args[]) { // About the simplest program you can // you can write in Java // Print “Hello World” to the console System.out.println(“Hello World”); } } 30-Apr-17 Air Force Institute of Technology Electrical and Computer Engineering 5 Object-Oriented Programming Design Java Programming Environment • Compiling the program javac HelloWorld.java • Running the program java HelloWorld • CLASSPATH environment variable – Do not define it unless you know what you are doing – If you do define it, ensure you include a period: set CLASSPATH=.;c:\java; 30-Apr-17 Air Force Institute of Technology Electrical and Computer Engineering 6