java aco101: introduction to computer science. the history of java started out as a research project...
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The History of Java
• Started out as a research project at Sun Microsystems in 1991
• Code named “Green”• Based on C and C++• Originally called “Oak” because its creator
James Gosling had an oak tree outside his office window at Sun.
History of Java – part 2
• They had to change the name from “Oak” to something else because it was discovered that there was already a language called “Oak” .
• A group of people at Sun went for coffee one day and someone suggested “Java” and it stuck.
• Between 1991 and 1993 the project faltered because Sun had anticipated that the smart consumer device market would grow faster than it did.
Java History – part 3
• When the internet boomed in 1993 the project got a new life because people saw the potential to create dynamic content for the web.
• “Java” was officially announced in May 1995.
Religious discussion
• Java vs. C#• James Gosling and Bill Joy (one of the
founders of Sun Microsystems) called C# an "imitation" of Java;
• Gosling (originator of Java) further claimed that "[C# is] sort of Java with reliability, productivity and security deleted."
More religious debate
• Klaus Kreft and Angelika Langer (authors of a C++ streams book) stated in a blog post that "Java and C# are almost identical programming languages. Boring repetition that lacks innovation."
• Anders Hejlsberg (lead the C# team) has argued that C# is "not a Java clone" and is "much closer to C++" in its design.
Why do you care?
• Because you will have to decide where you are in the debate and that will inform your career path.
• http://www.sun.com/lawsuit/• http://www.theregister.co.uk/2010/08/13/
oracle_sues_google/• http://regmedia.co.uk/2010/08/13/
oracle_complaint_against_google.pdf
Technology is constantly moving forward
• And so you will move forward with it. • I will not tell you what to think or how to be; I
will only give you the information to decide for yourself.
Knowing Both
• They are so similar that– If you know Java then you pretty much know C#
and knowing both will double your job opportunities.• http://www.indeed.com/
• Programming is one of the professions that the more you know the more you earn.
Runtime environments
Java • Java Runtime Environment
– Includes the JVM and Common Code Libraries
• JVM = Java Virtual Machine• The JRE was originally
designed to support interpreted execution with final compilation as an option.
• The Java compiler produces Java bytecode
C#• Common Language Runtime• The CLR is designed to
execute fully compiled code.
• The C# compiler produces Common Intermediate Language instructions.
Program execution
Java• bytecode is loaded by the
Java runtime and either interpreted directly or compiled to machine instructions and then executed
C#• the runtime loads Common
Intermediate Language code and compiles to machine instructions on the target architecture
Side bar: bytecode and CIL instructions
• A Java programmer does not need to be aware of or understand Java bytecode at all.
• However, "Understanding bytecode and what bytecode is likely to be generated by a Java compiler helps the Java programmer in the same way that knowledge of assembler helps the C or C++ programmer.“ – Peter Haggar IBM
• The same is true for CIL instructions and C#
We are not going that deep.
• If you are interested – here are some links; but this is Intro and you are not required to understand bytecode, CIL instructions or machine code on a deeper level.– http://www.ibm.com/developerworks/ibm/
library/it-haggar_bytecode/– http://en.csharp-online.net/CIL_Instruction_Set
Lets check to see if the JDK is installed
• Go to Start > Run > type “cmd” in the box to launch a command prompt– Type in the window (where the cursor is)
java –version
• C:\Program Files\Java– Is there a folder named jdk1.6.0_21
• click into the bin in that folder– C:\Program Files\Java\jdk1.6.0_21\bin– javac.exe is the compiler
To DIY you will need
• The Java SE Development Kit 6 (JDK 6) – http://www.oracle.com/technetwork/java/javase/
downloads/index.html– Read the installation instructions
• http://www.oracle.com/technetwork/java/javase/index-137561.html
– Click on the Download JDK button• I registered (you don’t have to)• Pick your platform and click continue• Click on the link provided to download the exe• Save file, double click and run
Hello world
• We havta do the tradition…. It would be just wrong to not have your first program be “Hello World”
• Open notepad (on a mac you can use simple text) and type this code…..
class myfirstjavaprog{ public static void main(String args[]) { System.out.println("Hello World!"); }}
Let’s run it – go to the location of the class (current working directory) and pass the name of the
class to the Java runtime
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