Java Development Kit
The Java Development Kit (JDK) is an implementation of either one of the Java SE, Java EE or Java ME platforms released by Oracle Corporation in the form of a binary product aimed at Java developers on Solaris, Linux, Mac OS X or Windows. Since the introduction of Java platform, it has been by far the most widely used Software Development Kit (SDK). On 17 November 2006, Sun announced that it would be released under the GNU General Public License (GPL), thus making it free software. This happened in large part on 8 May 2007, when Sun contributed the source code to the OpenJDK.
The JDK has as its primary components a collection of programming tools, including:
- appletviewer – this tool can be used to run and debug Java applets without a web browser
- apt – the annotation-processing tool
- extcheck – a utility which can detect JAR-file conflicts
- idlj – the IDL-to-Java compiler. This utility generates Java bindings from a given Java IDL file.
- java – the loader for Java applications. This tool is an interpreter and can interpret the class files generated by the javac compiler. Now a single launcher is used for both development and deployment. The old deployment launcher, jre, no longer comes with Sun JDK, and instead it has been replaced by this new java loader.
- javac – the Java compiler, which converts source code into Java bytecode
- javadoc – the documentation generator, which automatically generates documentation from source code comments
- jar – the archiver, which packages related class libraries into a single JAR file. This tool also helps manage JAR files.
- javah – the C header and stub generator, used to write native methods
- javap – the class file disassembler
- javaws – the Java Web Start launcher for JNLP applications
- JConsole – Java Monitoring and Management Console
- jdb – the debugger
- jhat – Java Heap Analysis Tool (experimental)
- jinfo – This utility gets configuration information from a running Java process or crash dump. (experimental)
- jmap – This utility outputs the memory map for Java and can print shared object memory maps or heap memory details of a given process or core dump. (experimental)
- jps – Java Virtual Machine Process Status Tool lists the instrumented HotSpot Java Virtual Machines (JVMs) on the target system. (experimental)
- jrunscript – Java command-line script shell.
- jstack – utility which prints Java stack traces of Java threads (experimental)
- jstat – Java Virtual Machine statistics monitoring tool (experimental)
- jstatd – jstat daemon (experimental)
- keytool – tool for manipulating the keystore
- pack200 – JAR compression tool
- policytool – the policy creation and management tool, which can determine policy for a Java runtime, specifying which permissions are available for code from various sources
- VisualVM – visual tool integrating several command-line JDK tools and lightweight performance and memory profiling capabilities
- wsimport – generates portable JAX-WS artifacts for invoking a web service.
- xjc – Part of the Java API for XML Binding (JAXB) API. It accepts an XML schema and generates Java classes.
Experimental tools may not be available in future versions of the JDK.
The JDK also comes with a complete Java Runtime Environment, usually called a private runtime, due to the fact that it is separated from the "regular" JRE and has extra contents. It consists of a Java Virtual Machine and all of the class libraries present in the production environment, as well as additional libraries only useful to developers, such as the internationalization libraries and the IDL libraries.
Copies of the JDK also include a wide selection of example programs demonstrating the use of almost all portions of the Java API.
Ambiguity between a JDK and an SDK
The JDK forms an extended subset of a software development kit (SDK). In the descriptions that accompany its recent releases, which implement Java SE, EE and ME, Sun acknowledges that under its terminology, the JDK forms the subset of the SDK which has the responsibility for the writing and running of Java programs. The remainder of the SDK comprises extra software, such as application servers, debuggers, and documentation.
In addition to the most widely used JDK discussed in this article, there are other JDKs commonly available for a variety of platforms, some of which started from the Sun JDK source and some which did not. All of them adhere to the basic Java specifications, but they often differ in explicitly unspecified areas, such as garbage collection, compilation strategies, and optimization techniques. They include:
In development or in maintenance mode:
- OpenJDK / IcedTea;
- GNU's Classpath and GCJ (The GNU Compiler for Java);
- Aicas JamaicaVM;
- IBM J9 JDK, for AIX, Linux, Windows, MVS, OS/400, Pocket PC, z/OS;
- Oracle Corporation's JRockit JDK, for Windows, Linux, and Solaris;
Not being maintained or discontinued:
Here is a typical photo of Sun Tech Days Java events, this one held in Spain.
Patrick Naughton (born in 1965) is an American software developer, best known as being one of the original creators of the Java programming language.
As a Sun engineer, Patrick Naughton had become increasingly frustrated with the state of Sun's C++ and C APIs (application programming interfaces) and tools. While considering moving to NeXT, Naughton was offered a chance to work on new technology and thus the Stealth Project was started.
The Stealth Project was soon renamed to the Green Project with James Gosling and Mike Sheridan joining Naughton. Together with other engineers, they began work in a small office on Sand Hill Road in Menlo Park, California. They were attempting to develop a new technology for programming next generation smart appliances, which Sun expected to be a major new opportunity.
In June and July 1994, after three days of brainstorming with John Gage, the Director of Science for Sun, James Gosling, Bill Joy, Naughton, Wayne Rosing, and Eric Schmidt, the team re-targeted the platform for the World Wide Web. They felt that with the advent of the first graphical web browser, Mosaic, the Internet was on its way to evolving into the same highly interactive medium that they had envisioned for cable TV. As a prototype, Naughton wrote a small browser, WebRunner, later renamed HotJava.
- ... that Java SE 6 is code-named Mustang?
- ... that Duke is Java's mascot and "smart agent" assisting the user in PDA?
1. Who said: "There's only one trick in software, and that is using a piece of software that's already been written."?
2. When was Java first released?
4. Which was Java's original name: Green, Oak, Stealth, C++ ++ --, firstperson, Duke or Coffee?
5. True or False: An Interface can never be private or protected?
- Answer (External link)