Java (programming language) explained

Java
Paradigm:multi-paradigm

object-oriented, structured, imperative, generic, reflective

Designer:James Gosling and
Sun Microsystems
Developer:Oracle Corporation
Latest Release Version:Java Standard Edition 7 Update 3 (1.7.3)
Turing-Complete:Yes
Typing:Static, strong, safe, nominative, manifest
Implementations:OpenJDK, many others
Influenced By:Ada 83, C++, C#,[1] Eiffel,[2] Generic Java, Mesa,[3] Modula-3,[4] Oberon,[5] Objective-C,[6] UCSD Pascal,[7] [8] Smalltalk
Influenced:Ada 2005, BeanShell, C#, Clojure, D, ECMAScript, Groovy, J#, JavaScript, PHP, Python, Scala, Vala
Dialects:Generic Java, Pizza
Operating System:Cross-platform (multi-platform)
License:GNU General Public License, Java Community Process
Website:For Java Developers
File Ext:.java, .class, .jar
Wikibooks:Java Programming

Java is a programming language originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode (class file) that can run on any Java Virtual Machine (JVM) regardless of computer architecture.Java is a general-purpose, concurrent, class-based, object-oriented language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA), meaning that code that runs on one platform does not need to be recompiled to run on another. Java is currently one of the most popular programming languages in use, particularly for client-server web applications, with a reported 10 million users.[9] [10]

The original and reference implementation Java compilers, virtual machines, and class libraries were developed by Sun from 1995. As of May 2007, in compliance with the specifications of the Java Community Process, Sun relicensed most of its Java technologies under the GNU General Public License. Others have also developed alternative implementations of these Sun technologies, such as the GNU Compiler for Java and GNU Classpath.

History

James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991.[11] Java was originally designed for interactive television, but it was too advanced for the digital cable television industry at the time.[12] The language was initially called Oak after an oak tree that stood outside Gosling's office; it went by the name Green later, and was later renamed Java, from Java coffee, said to be consumed in large quantities by the language's creators.[13] Gosling aimed to implement a virtual machine and a language that had a familiar C/C++ style of notation.[14]

Sun Microsystems released the first public implementation as Java 1.0 in 1995. It promised "Write Once, Run Anywhere" (WORA), providing no-cost run-times on popular platforms. Fairly secure and featuring configurable security, it allowed network- and file-access restrictions. Major web browsers soon incorporated the ability to run Java applets within web pages, and Java quickly became popular. With the advent of Java 2 (released initially as J2SE 1.2 in December 1998–1999), new versions had multiple configurations built for different types of platforms. For example, J2EE targeted enterprise applications and the greatly stripped-down version J2ME for mobile applications (Mobile Java). J2SE designated the Standard Edition. In 2006, for marketing purposes, Sun renamed new J2 versions as Java EE, Java ME, and Java SE, respectively.

In 1997, Sun Microsystems approached the ISO/IEC JTC1 standards body and later the Ecma International to formalize Java, but it soon withdrew from the process.[15] Java remains a de facto standard, controlled through the Java Community Process.[16] At one time, Sun made most of its Java implementations available without charge, despite their proprietary software status. Sun generated revenue from Java through the selling of licenses for specialized products such as the Java Enterprise System. Sun distinguishes between its Software Development Kit (SDK) and Runtime Environment (JRE) (a subset of the SDK); the primary distinction involves the JRE's lack of the compiler, utility programs, and header files.

On November 13, 2006, Sun released much of Java as free and open source software, (FOSS), under the terms of the GNU General Public License (GPL). On May 8, 2007, Sun finished the process, making all of Java's core code available under free software/open-source distribution terms, aside from a small portion of code to which Sun did not hold the copyright.[17]

Sun's vice-president Rich Green said that Sun's ideal role with regards to Java was as an "evangelist."[18] Following Oracle Corporation's acquisition of Sun Microsystems in 2009–2010, Oracle has described itself as the "steward of Java technology with a relentless commitment to fostering a community of participation and transparency".[19] Java software runs on laptops to data centers, game consoles to scientific supercomputers. There are 930 million Java Runtime Environment downloads each year and 3 billion mobile phones run Java.[20] On April 2, 2010, James Gosling resigned from Oracle.[21]

Principles

There were five primary goals in the creation of the Java language:[22]

  1. It should be "simple, object-oriented and familiar"
  2. It should be "robust and secure"
  3. It should be "architecture-neutral and portable"
  4. It should execute with "high performance"
  5. It should be "interpreted, threaded, and dynamic"

Versions

See main article: Java version history. Major release versions of Java, along with their release dates:

Practices

Java platform

See main article: Java (software platform) and Java Virtual Machine.

One characteristic of Java is portability, which means that computer programs written in the Java language must run similarly on any hardware/operating-system platform.This is achieved by compiling the Java language code to an intermediate representation called Java bytecode, instead of directly to platform-specific machine code. Java bytecode instructions are analogous to machine code, but are intended to be interpreted by a virtual machine (VM) written specifically for the host hardware. End-users commonly use a Java Runtime Environment (JRE) installed on their own machine for standalone Java applications, or in a Web browser for Java applets.

Standardized libraries provide a generic way to access host-specific features such as graphics, threading, and networking.

A major benefit of using bytecode is porting. However, the overhead of interpretation means that interpreted programs almost always run more slowly than programs compiled to native executables would. Just-in-Time (JIT) compilers were introduced from an early stage that compile bytecodes to machine code during runtime.

Implementations

Sun Microsystems officially licensed the Java Standard Edition platform for Linux,[23] Mac OS X,[24] and Solaris. In the past Sun licensed Java to Microsoft but the license expired without renewal.[25] Because Windows does not ship with a Java software platform, a network of third-party vendors and licensees[26] develop them for Windows and other operating system/hardware platforms.

Sun's trademark license for usage of the Java brand insists that all implementations be "compatible". This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun.[27] As a result, Microsoft no longer ships Java with Windows, and in recent versions of Windows, Internet Explorer cannot support Java applets without a third-party plugin. Sun, and others, have made available free Java run-time systems for those and other versions of Windows.

Platform-independent Java is essential to the Java EE strategy, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications, such as Web services, Java Servlets, and Enterprise JavaBeans, as well as with embedded systems based on OSGi, using Embedded Java environments. Through the GlassFish project, Sun is working to create a fully functional, unified open source implementation of the Java EE technologies.

Sun also distributes a superset of the JRE called the Java Development Kit (commonly known as the JDK), which includes development tools such as the Java compiler, Javadoc, Jar, and debugger.

Performance

See main article: Java performance.

Programs written in Java have a reputation for being slower and requiring more memory than those written in C.[28] However, Java programs' execution speed improved significantly with the introduction of Just-in-time compilation in 1997/1998 for Java 1.1,[29] the addition of language features supporting better code analysis (such as inner classes, StringBuffer class, optional assertions, etc.), and optimizations in the Java Virtual Machine itself, such as HotSpot becoming the default for Sun's JVM in 2000. Currently (February 2012), microbenchmarks show Java 7 is approximately 1.5 times slower than C.[30]

Some platforms offer direct hardware support for Java; there are microcontrollers that can run Java in hardware instead of a software Java Virtual Machine, and ARM based processors can have hardware support for executing Java bytecode through its Jazelle option.

Automatic memory management

Java uses an automatic garbage collector to manage memory in the object lifecycle. The programmer determines when objects are created, and the Java runtime is responsible for recovering the memory once objects are no longer in use. Once no references to an object remain, the unreachable memory becomes eligible to be freed automatically by the garbage collector. Something similar to a memory leak may still occur if a programmer's code holds a reference to an object that is no longer needed, typically when objects that are no longer needed are stored in containers that are still in use. If methods for a nonexistent object are called, a "null pointer exception" is thrown.[31] [32]

One of the ideas behind Java's automatic memory management model is that programmers can be spared the burden of having to perform manual memory management. In some languages, memory for the creation of objects is implicitly allocated on the stack, or explicitly allocated and deallocated from the heap. In the latter case the responsibility of managing memory resides with the programmer. If the program does not deallocate an object, a memory leak occurs. If the program attempts to access or deallocate memory that has already been deallocated, the result is undefined and difficult to predict, and the program is likely to become unstable and/or crash. This can be partially remedied by the use of smart pointers, but these add overhead and complexity. Note that garbage collection does not prevent "logical" memory leaks, i.e. those where the memory is still referenced but never used.

Garbage collection may happen at any time. Ideally, it will occur when a program is idle. It is guaranteed to be triggered if there is insufficient free memory on the heap to allocate a new object; this can cause a program to stall momentarily. Explicit memory management is not possible in Java.

Java does not support C/C++ style pointer arithmetic, where object addresses and unsigned integers (usually long integers) can be used interchangeably. This allows the garbage collector to relocate referenced objects and ensures type safety and security.

As in C++ and some other object-oriented languages, variables of Java's primitive data types are not objects. Values of primitive types are either stored directly in fields (for objects) or on the stack (for methods) rather than on the heap, as commonly true for objects (but see Escape analysis). This was a conscious decision by Java's designers for performance reasons. Because of this, Java was not considered to be a pure object-oriented programming language. However, as of Java 5.0, autoboxing enables programmers to proceed as if primitive types were instances of their wrapper class.

Java contains multiple types of garbage collectors. By default, HotSpot uses the Concurrent Mark Sweep collector, also known as the CMS Garbage Collector. However, there are also several other garbage collectors that can be used to manage the Heap. For 90% of applications in Java, the CMS Garbage Collector is good enough.[33]

Syntax

See main article: Java syntax.

The syntax of Java is largely derived from C++. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object-oriented language. All code is written inside a class, and everything is an object, with the exception of the primitive data types (integers, floating-point numbers, boolean values, and characters), which are not classes for performance reasons.

Unlike C++, Java does not support operator overloading or multiple inheritance for classes. This simplifies the language and aids in preventing potential errors and anti-pattern design.

Java uses similar commenting methods to C++. There are three different styles of comments: a single line style marked with two slashes (//), a multiple line style opened with /* and closed with */, and the Javadoc commenting style opened with /** and closed with */. The Javadoc style of commenting allows the user to run the Javadoc executable to compile documentation for the program.

Example:

java

// This is an example of a single line comment using two slashes

/* This is an example of a multiple line comment using the slash and asterisk.
   This type of comment can be used to hold a lot of information or deactivate
   code but it is very important to remember to close the comment. */

/**
 * This is an example of a Javadoc comment; Javadoc can compile documentation
 *  from this text.
 */

Examples

Hello world

The traditional Hello world program can be written in Java as:[34]

java

class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}
To compare this to other programming languages see the list of hello world program examples.

Source files must be named after the public class they contain, appending the suffix .java, for example, HelloWorldApp.java. It must first be compiled into bytecode, using a Java compiler, producing a file named HelloWorldApp.class. Only then can it be executed, or 'launched'. The Java source file may only contain one public class but can contain multiple classes with less than public access and any number of public inner classes.

A '''class''' that is not declared '''public''' may be stored in any .java file. The compiler will generate a class file for each class defined in the source file. The name of the class file is the name of the class, with .class appended. For class file generation, anonymous classes are treated as if their name were the concatenation of the name of their enclosing class, a $, and an integer.

The keyword '''public''' denotes that a method can be called from code in other classes, or that a class may be used by classes outside the class hierarchy. The class hierarchy is related to the name of the directory in which the .java file is located.

The keyword '''static''' in front of a method indicates a static method, which is associated only with the class and not with any specific instance of that class. Only static methods can be invoked without a reference to an object. Static methods cannot access any class members that are not also static.

The keyword '''void''' indicates that the main method does not return any value to the caller. If a Java program is to exit with an error code, it must call System.exit explicitly.

The method name "main" is not a keyword in the Java language. It is simply the name of the method the Java launcher calls to pass control to the program. Java classes that run in managed environments such as applets and Enterprise JavaBean do not use or need a main method. A Java program may contain multiple classes that have main methods, which means that the VM needs to be explicitly told which class to launch from.

The main method must accept an array of objects. By convention, it is referenced as '''args''' although any other legal identifier name can be used. Since Java 5, the main method can also use variable arguments, in the form of public static void main(String... args), allowing the main method to be invoked with an arbitrary number of String arguments. The effect of this alternate declaration is semantically identical (the args parameter is still an array of String objects), but allows an alternative syntax for creating and passing the array.

The Java launcher launches Java by loading a given class (specified on the command line or as an attribute in a JAR) and starting its public static void main(String[]) method. Stand-alone programs must declare this method explicitly. The String[] args parameter is an array of objects containing any arguments passed to the class. The parameters to main are often passed by means of a command line.

Printing is part of a Java standard library: The class defines a public static field called . The out object is an instance of the class and provides many methods for printing data to standard out, including which also appends a new line to the passed string.

The string "Hello, world!" is automatically converted to a String object by the compiler.

A more comprehensive example

java

// OddEven.java
import javax.swing.JOptionPane;

public class OddEven {
    /**
     * "input" is the number that the user gives to the computer
     */
    private int input; // a whole number("int" means integer)

    /**
     * This is the constructor method. It gets called when an object of the OddEven type
     * is being created.
     */
    public OddEven {
    /*
     * In most Java programs constructors can initialize objects with default values, or create
     * other objects that this object might use to perform its functions. In some Java programs, the
     * constructor may simply be an empty function if nothing needs to be initialized prior to the
     * functioning of the object.  In this program's case, an empty constructor would suffice, even if
     * it is empty. A constructor must exist, however if the user doesn't put one in then the compiler
     * will create an empty one.
     */
    }

    /**
     * This is the main method. It gets called when this class is run through a Java interpreter.
     * @param args command line arguments (unused)
     */
    public static void main(final String[] args) {
        /*
         * This line of code creates a new instance of this class called "number" (also known as an
         * Object) and initializes it by calling the constructor.  The next line of code calls
         * the "showDialog" method, which brings up a prompt to ask you for a number
         */
        OddEven number = new OddEven;
        number.showDialog;
    }

    public void showDialog {
        /*
         * "try" makes sure nothing goes wrong. If something does,
         * the interpreter skips to "catch" to see what it should do.
         */
        try {
            /*
             * The code below brings up a JOptionPane, which is a dialog box
             * The String returned by the "showInputDialog" method is converted into
             * an integer, making the program treat it as a number instead of a word.
             * After that, this method calls a second method, calculate that will
             * display either "Even" or "Odd."
             */
            this.input = Integer.parseInt(JOptionPane.showInputDialog("Please Enter A Number"));
            this.calculate;
        } catch (final NumberFormatException e) {
            /*
             * Getting in the catch block means that there was a problem with the format of
             * the number. Probably some letters were typed in instead of a number.
             */
            System.err.println("ERROR: Invalid input. Please type in a numerical value.");
        }
    }

    /**
     * When this gets called, it sends a message to the interpreter.
     * The interpreter usually shows it on the command prompt (For Windows users)
     * or the terminal (For *nix users).(Assuming it's open)
     */
    private void calculate {
        if ((this.input % 2) == 0) {
            JOptionPane.showMessageDialog(null, "Even");
        } else {
            JOptionPane.showMessageDialog(null, "Odd");
        }
    }
}

Special classes

Applet

See main article: Java applet.

Java applets are programs that are embedded in other applications, typically in a Web page displayed in a Web browser.

java

// Hello.java
import javax.swing.JApplet;
import java.awt.Graphics;

public class Hello extends JApplet {
    public void paintComponent(final Graphics g) {
        g.drawString("Hello, world!", 65, 95);
    }
}

The '''import''' statements direct the Java compiler to include the and classes in the compilation. The import statement allows these classes to be referenced in the source code using the simple class name (i.e. JApplet) instead of the fully qualified class name (i.e. javax.swing.JApplet).

The Hello class '''extends''' (subclasses) the '''JApplet''' (Java Applet) class; the JApplet class provides the framework for the host application to display and control the lifecycle of the applet. The JApplet class is a JComponent (Java Graphical Component) which provides the applet with the capability to display a graphical user interface (GUI) and respond to user events.

The Hello class overrides the method (additionally indicated with the annotation, supported as of JDK 1.5, Override) inherited from the superclass to provide the code to display the applet. The paintComponent method is passed a '''Graphics''' object that contains the graphic context used to display the applet. The paintComponent method calls the graphic context method to display the "Hello, world!" string at a pixel offset of ('''65, 95''') from the upper-left corner in the applet's display.

html4strict

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<!-- Hello.html -->
<html>
  <head>
    <title>Hello World Applet</title>
  </head>
  <body>
    <applet code="Hello.class" width="200" height="200">
    </applet>
  </body>
</html>

An applet is placed in an HTML document using the <applet> HTML element. The applet tag has three attributes set: code="Hello" specifies the name of the JApplet class and width="200" height="200" sets the pixel width and height of the applet. Applets may also be embedded in HTML using either the object or embed element,[35] although support for these elements by Web browsers is inconsistent.[36] However, the applet tag is deprecated, so the object tag is preferred where supported.

The host application, typically a Web browser, instantiates the Hello applet and creates an for the applet. Once the applet has initialized itself, it is added to the AWT display hierarchy. The paintComponent method is called by the AWT event dispatching thread whenever the display needs the applet to draw itself.

Servlet

See main article: Java Servlet.

Java Servlet technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems. Servlets are server-side Java EE components that generate responses (typically HTML pages) to requests (typically HTTP requests) from clients. A servlet can almost be thought of as an applet that runs on the server side—without a face.

java

// Hello.java
import java.io.*;
import javax.servlet.*;

public class Hello extends GenericServlet
{
    public void service(final ServletRequest request,final ServletResponse response)
            throws ServletException, IOException
     {
       response.setContentType("text/html");
       final PrintWriter pw = response.getWriter;
       try {
           pw.println("Hello, world!");
       } finally {
           pw.close;
       }
   }
}

The import statements direct the Java compiler to include all of the public classes and interfaces from the and packages in the compilation.

The '''Hello''' class '''extends''' the class; the GenericServlet class provides the interface for the server to forward requests to the servlet and control the servlet's lifecycle.

The Hello class overrides the method defined by the interface to provide the code for the service request handler. The service method is passed a object that contains the request from the client and a object used to create the response returned to the client. The service method declares that it '''throws''' the exceptions and if a problem prevents it from responding to the request.

The method in the response object is called to set the MIME content type of the returned data to "text/html". The method in the response returns a object that is used to write the data that is sent to the client. The method is called to write the "Hello, world!" string to the response and then the method is called to close the print writer, which causes the data that has been written to the stream to be returned to the client.

JavaServer Pages

See main article: JavaServer Pages.

JavaServer Pages (JSP) are server-side Java EE components that generate responses, typically HTML pages, to HTTP requests from clients. JSPs embed Java code in an HTML page by using the special delimiters <% and %>. A JSP is compiled to a Java servlet, a Java application in its own right, the first time it is accessed. After that, the generated servlet creates the response.

Swing application

See main article: Swing (Java).

Swing is a graphical user interface library for the Java SE platform. It is possible to specify a different look and feel through the pluggable look and feel system of Swing. Clones of Windows, GTK+ and Motif are supplied by Sun. Apple also provides an Aqua look and feel for Mac OS X. Where prior implementations of these looks and feels may have been considered lacking, Swing in Java SE 6 addresses this problem by using more native GUI widget drawing routines of the underlying platforms.

This example Swing application creates a single window with "Hello, world!" inside:

java

// Hello.java (Java SE 5)
import javax.swing.*;

public class Hello extends JFrame {
    public Hello {
        super("hello");
        super.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        super.add(new JLabel("Hello, world!"));
        super.pack;
        super.setVisible(true);
    }

    public static void main(final String[] args) {
        new Hello;
    }
}

The first import includes all of the public classes and interfaces from the package.

The '''Hello''' class '''extends''' the class; the JFrame class implements a window with a title bar and a close control.

The '''Hello''' constructor initializes the frame by first calling the superclass constructor, passing the parameter "hello", which is used as the window's title. It then calls the method inherited from JFrame to set the default operation when the close control on the title bar is selected to — this causes the JFrame to be disposed of when the frame is closed (as opposed to merely hidden), which allows the Java Virtual Machine to exit and the program to terminate. Next, a is created for the string "Hello, world!" and the method inherited from the superclass is called to add the label to the frame. The method inherited from the superclass is called to size the window and lay out its contents.

The '''main''' method is called by the Java Virtual Machine when the program starts. It instantiates a new Hello frame and causes it to be displayed by calling the method inherited from the superclass with the boolean parameter '''true'''. Once the frame is displayed, exiting the main method does not cause the program to terminate because the AWT event dispatching thread remains active until all of the Swing top-level windows have been disposed.

Generics

See main article: Generics in Java.

In 2004, generics were added to the Java language, as part of J2SE 5.0. Prior to the introduction of generics, each variable declaration had to be of a specific type. For container classes, for example, this is a problem because there is no easy way to create a container that accepts only specific types of objects. Either the container operates on all subtypes of a class or interface, usually Object, or a different container class has to be created for each contained class. Generics allow compile-time type checking without having to create a large number of container classes, each containing almost identical code. In addition to enabling more efficient code, certain runtime exceptions are converted to compile-time exceptions, a characteristic known as type safety.

Criticism

See main article: Criticism of Java. A number of criticisms have been leveled at Java for various design choices in the language and platform. Such criticisms include the implementation of generics, the speed of Java, [37] the handling of unsigned numbers,[38] the implementation of floating-point arithmetic,[39] and a history of security vulnerabilities in the primary Java VM implementation HotSpot.[40]

Use by external companies

Google

Google and Android, Inc. have chosen to use Java as a key pillar in the creation of the Android operating system, an open-source smartphone operating system. Besides the fact that the operating system, built on the Linux 2.6 kernel, was written largely in Java, the Android SDK uses Java to design applications for the Android platform.

Class libraries

Documentation

See main article: Javadoc. Javadoc is a comprehensive documentation system, created by Sun Microsystems, used by many Java developers. It provides developers with an organized system for documenting their code. Javadoc comments have an extra asterisk at the beginning, i.e. the tags are /** and */, whereas the normal multi-line comments in Java are set off with the tags /* and */.

Editions

Sun has defined and supports four editions of Java targeting different application environments and segmented many of its APIs so that they belong to one of the platforms. The platforms are:

The classes in the Java APIs are organized into separate groups called packages. Each package contains a set of related interfaces, classes and exceptions. Refer to the separate platforms for a description of the packages available.

The set of APIs is controlled by Sun Microsystems in cooperation with others through the Java Community Process program. Companies or individuals participating in this process can influence the design and development of the APIs. This process has been a subject of controversy.

Sun also provided an edition called PersonalJava that has been superseded by later, standards-based Java ME configuration-profile pairings.

See also

References

External links

Notes and References

  1. Java 5.0 added several new language features (the enhanced for loop, autoboxing, varargs and annotations), after they were introduced in the similar (and competing) C# language http://www.barrycornelius.com/papers/java5/http://www.levenez.com/lang/
  2. Web site: Gosling, James; and McGilton, Henry. The Java Language Environment. May 1996.
  3. Web site: Gosling, James; Joy, Bill; Steele, Guy; and Bracha, Gilad. The Java Language Specification, 2nd Edition.
  4. Web site: The A-Z of Programming Languages: Modula-3. Computerworld.com.au. 2010-06-09.
  5. [Niklaus Wirth]
  6. [Patrick Naughton]
  7. Web site: History of Java. The project went ahead under the name "green" and the language was based on an old model of UCSD Pascal, which makes it possible to generate interpretive code. Java Application Servers Report. TechMetrix Research. 1999.
  8. Web site: A Conversation with James Gosling – ACM Queue. Queue.acm.org. 2004-08-31. 2010-06-09.
  9. Web site: Programming Language Popularity. 2009. 2009-01-16.
  10. Web site: TIOBE Programming Community Index. 2009. 2009-05-06.
  11. Web site: Java technology: The early years. http://web.archive.org/web/20050420081440/http://java.sun.com/features/1998/05/birthday.html. 2005-04-20,April 20, 2005. Byous. Jon. ca. 1998. Sun Developer Network. Sun Microsystems. 2005-04-22.
  12. Web site: The History of Java Technology. ca. 1995. Sun Developer Network. 2010-04-30.
  13. Web site: Java - definition of Java by the Free Online Dictionary, Thesaurus and Encyclopedia.. 2003-06-15. 2011-07-30.
  14. Kabutz, Heinz; Once Upon an Oak. Artima. Retrieved April 29, 2007.
  15. http://www.open-std.org/JTC1/SC22/JSG/ Java Study Group
  16. Web site: Java Community Process website. Jcp.org. 2010-05-24. 2010-06-09.
  17. Web site: JAVAONE: Sun – The bulk of Java is open sourced. open.itworld.com. 2010-06-09.
  18. Web site: Sun’s Evolving Role as Java Evangelist. O'Reilly Media.
  19. Web site: Oracle and Java. oracle.com. Oracle Corporation. 2010-08-23. Oracle has been a leading and substantive supporter of Java since its emergence in 1995 and takes on the new role as steward of Java technology with a relentless commitment to fostering a community of participation and transparency..
  20. Web site: Learn About Java Technology. Oracle. 21 November 2011.
  21. Web site: Time to move on.... Gosling. James. April 9, 2010. On a New Road. 2011-11-16. James Gosling.
  22. Web site: 1.2 Design Goals of the JavaTM Programming Language. http://java.sun.com/docs/white/langenv/Intro.doc2.html. 1999-01-01. 2010-06-09.
  23. Web site: Sun Embraces Linux With New Java License. Web Media Brands. Internet News. Patrizio, Andy. 2006. 2009-09-29.
  24. Web site: Java for Mac OS X. Apple. Apple Developer Connection. 2009-09-29.
  25. Web site: Microsoft Java Virtual Machine Support. Microsoft.com. 2010-06-09.
  26. Web site: Java SE – Licensees. Java.sun.com. 2008-08-12. 2010-06-09.
  27. News: Niccolai, James. Sun, Microsoft settle Java lawsuit. JavaWorld. IDG. January 23, 2001. 2008-07-09.
  28. Web site: Why Java will always be slower than C++. Jelovic. Dejan. 2008-02-15.
  29. Web site: Symantec's Just-In-Time Java Compiler To Be Integrated Into Sun JDK 1.1.
  30. http://shootout.alioth.debian.org/u32q/which-programming-languages-are-fastest.php?gcc=on&javasteady=on&java=on&csharp=on&javaxint=on&calc=chart
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