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Unformatted text preview: CMPT 125: Lecture 2 Introduction to Java Tamara Smyth, firstname.lastname@example.org School of Computing Science, Simon Fraser University January 3, 2009 1 Brief History of Java • Java was developed by James Gosling and his team at Sun Computers in the early 1990s. • Originally called Oak, later given the name Java: – inspired by a coffee bean? – or an acronym for the names of the team members: J ames Gosling, A rthur V an Hoff, and A ndy Bechtolsheim? • Though now often thought of as a program designed for the world wide web, it was originally meant to be a programming language for embedded systems. • As the web gained in popularity in 1994, the HotJava browser was a good demo of Java’s capabilities: platform independence and security. • Java released publicly in 1995. CMPT 125: Introduction to Java, Lecture 2 2 Java Versions • We will use Java version 1.5 (5.0) which includes some major enhancements to previous versions of Java (so watch out for this if you’re using older textbooks!). • Regularly consult the following website (keep it bookmarked!) for the API specification: http://java.sun.com/j2se/1.5.0/docs/api/. CMPT 125: Introduction to Java, Lecture 2 3 Some Java Details • Java syntax is (purposely) similar to C/C++ syntax. • Java supports the object-oriented programming paradigm (OOP). • Because of OOP, some simple programs tend to be overly complex in Java. • Java was not designed with beginners in mind, but it is arguably easier to learn than C/C++. • Java uses a garbage collector to help manage memory. • For some applications Java is a little slower than C/C++ but tends to be much faster than (say) Python. CMPT 125: Introduction to Java, Lecture 2 4 Translating and Executing Java Programs • All source code is first written in plain text files ending with the .java extension. • Source files are then compiled to produce .class files. • A .class file does not contain code that is native to your processor. Rather, it contains bytecode , the machine language of the Java Virtual Machine (Java VM). • The java launcher tool then runs your application with an instance of the Java VM. Figure 1: MyProgram.java is compiled to produce MyProgram.class, which is then inter- preted by the Java VM before My Program runs on a computer. CMPT 125: Introduction to Java, Lecture 2 5 Platform Independence • Because the Java VM is available on many different operating systems, the same .class files can run on different computers without recompiling. • The Java HotSpot virtual machine, perform additional steps at runtime to give your application a performance boost, including recompiling some frequently used code to native machine code....
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This note was uploaded on 12/07/2010 for the course CMPT 125 taught by Professor Diana during the Spring '08 term at Simon Fraser.
- Spring '08