Overview of Java CS 3250

A Brief History January 1996: first official release JDK 1.0 Web: applets, security, URL, networking GUI: Abstract Windows Toolkit (AWT) "To be blunt, Java 1.0 was not ready for prime time." Core Java, Vol. I, p. 9

A Brief History (continued) February 1997: JDK 1.1 Authentication: digital signatures, certificates Distributed computing: RMI, object serialization, Java IDL/CORBA Database connectivity: JDBC Component architecture: JavaBean Version 1.1 "filled in the most obvious gaps, greatly improved the reflection capability, and added a new event model for GUI programming. It was still rather limited, though." Core Java, Vol. I, p. 9

December 1998: Java 2 Platform (JDK 1.2) Standard, Enterprise, and Micro Editions JFC: Swing, Java2D, Java3D Java Cryptography Extension (JCE) Enterprise computing: enterprise JavaBean (EJB), servlets, Java server page (JSP), Jini, XML A Brief History (continued)

More changes in 1.2 (Java 2): Java Multimedia Framework (JMF) Embedded systems: KVM, JavaCard Performance enhancement: JIT, HotSpot VM A Brief History (continued) Version 1.2 "replaced the early toylike GUI and graphics toolkits with sophisticated and scalable versions that came a lot closer to the promise of 'Write Once, Run Anywhere' than their predecessors." Core Java, Vol. I, p. 10

Versions 1.3 and 1.4: incremental improvements to library, performance bug fixes A Brief History (continued) "During this time, much of the initial hype about Java applets and client-side applications abated, but Java became the platform of choice for server-side applications." Core Java, Vol. I, p. 10

Versions 5.0 (originally 1.5): significant changes to language, not just library generic classes features inspired by C# "for each" loop, autoboxing, metadata A Brief History (continued) "Language changes are always a source of compatibility pain, but several of these new language features are so seductive that we think programmers will embrace them eagerly." Core Java, Vol. I, p. 10

Evolution of Java VersionNew Language FeaturesClasses and Interfaces 1.0 The language itself Inner classes None None Assertions Generic classes, "for each" loop, varargs, autoboxing, metadata, enumerations, static import 3270 based on p. 10 of Core Java, Vol. I

Top 10 Reasons for Using Java Or, 10 ways to start an argument

10. Garbage Collected C and C++ are not, but most other modern languages are

9. Visual Studio Platform-specific Version problems Impossible to write a small program Lack of support for command-line tools Emacs, make, javac, java

8. Multi-threaded Runnable synchronized

7. Distributed Socket classes Remote Method Invocation (RMI) Serialization

6. GUI-less GUIs Can make a GUI with just a text editor Also, flexible GUIs (layouts)

5. Jobs Personally, I haven’t heard of a good way to measure this…

4. Pervasive “The Open Handset Alliance, a group of more than 30 technology and mobile companies, is developing Android: the first complete, open, and free mobile platform.” Also servlets, applets, JSP, current phone platforms

3. Linux, OS X Architecture neutral

2. Libraries Thousands of classes Comprehensive and useful documentation

And the number one reason is...

1. Portable, standard, and free Graphics and GUIs Near misses: wxWidgets (not standard, not particularly easy to use) QT (not free or standard) GTK (not standard).NET (not portable)

Top 10 reasons NOT to use Java You can’t say I’m biased…

10. Unity Unity? Huh? JavaScript, C#, Boo

9. ReallyLongVariableNamesAn dClassNamesForWhichJavaI sFamousOrInfamous

8. Java is “hard to teach” “Too many things that can’t be explained at the beginning” Do you believe it?

7. J2EE But, some people think this is Java’s niche

6. Java is the “new COBOL” Do you believe it?

5. Bad press Overhyped, misconceptions See Professor Allison’s D paper

4. Sun’s follies ME (and not working with Palm) Java Media Framework Java 3D Quicktime for Java (OK, that’s Apple’s) Is Oracle doing any better?

3. C# and the 900-pound gorilla

2. Python, JavaScript But, see Jython and Rhino Maybe Ruby, D, and maybe even PHP (but not Perl)

1. Performance Not as fast as C++ or C# Is it fast enough?

What’s Missing (vs. C++) Explicit pointers Delete operator Destructors References (pass-by-reference) Default arguments

What’s Missing (vs. C++) Globals Local static data Operator overloading Multiple (implementation) inheritance Separation of declaration and definition Templates (“generics” added in 1.5)

What’s New Everything resides in a class Data and functions Garbage collection Fewer memory management headaches Exceptions not optional Unicode encoding Portable: Threads Networking Data sizes

Java Architecture Java code is compiled into platform- independent “byte code” (“javac.exe”) Each class in its own.class file The Java Virtual Machine runs in the target environment (“java.exe”) Interprets the byte code Advantage: portability (“write-once-run- anywhere”) Disadvantage: degraded performance

JIT Compilation “Just-in-time” compilation The JVM has the JIT compiler compile the code into native machine code times faster than classic JVM interpretation

public class Hello { public static void main (String[] args) { System.out.println("Hello, world"); } First Java Application Every program must have at least one class Source file must be class name plus ".java"

public class Hello { public static void main (String[] args) { System.out.println("Hello, world"); } First Java Application The famous "magic formula" for the main method of a Java application:

Elements of Java Programs Class: Hello Method: main(...) Statement: System.out.println(...) Comments: // a comment /* another comment */ /** document comment */ Source file: Hello.java (case sensitive)

Development Environments Java SDK from Oracle command-line tools: javac, java, etc. no editor included netBeans (netbeans.org) IDE, including Java beans (components) Eclipse IDE (eclipse.org) IDE All of these are free See Ch. 2 and the web sites for more information.

Compile and Run an App using the Java SDK command-line tools To compile: javac Hello.java To run: java Hello