Java (programming language）
From Wikipedia， the free encyclopedia
Java is a programming language originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation） and relead 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-purpo，concurrent， class-bad， 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," meaning that code that runs on one platform does not need to be edited to run on another. Java is currently one of the most popular programming languages in u, particularly for client—rver web applications， with a reported 10 million urs.[10］[11] The original and reference implementation Java compile
rs， 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 relicend most of its Java technologies under the GNU General Public Licen。 Others have also developed alternative implementations of the Sun technologies， such as the GNU Compiler for Java and GNU Classpath.
Contents
1 History
1。1 Principles
1.2 Versions
2 Practices
2.1 Java platform
2。1。1 Implementations
2。1。2 Performance
2。2 Automatic memory management
History
凯德锦绣See also： Java (software platform)#History
James Gosling， Mike Sheridan， and Patrick Naughton initiated the Java language project in June 1991。［12] Java was originally designed for interactive television， but it was too advanced for the digital cable television industry at the time.[13］ 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.［14] Gosling aimed to implement a virtual machine and a language that had a familiar C/C++ style of notation。[15]
Sun Microsystems relead the first public implementation as Java 1。0 in 1995. It promid ”Write Once, Run Anywhere” （WORA）, providing no—cost run—times on po
pular platforms. Fairly cure and featuring configurable curity, it allowed network- and file—access restrictions。 Major web browrs soon incorporated the ability to run Java applets within web pages， and Java quickly became popular. With the advent of Java 2 （relead initially as J2SE 1。2 in December 1998–1999）， new versions had multiple configurations built for different types of platforms. For example， J2EE targeted enterpri applications and the greatly stripped—down version J2ME for mobile applications （Mobile Java）。 J2SE designated the Standard Edition。 In 2006, for marketing purpos， 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爱国视频 事业单位等级withdrew from the process。[16] Java remains a de facto standard, controlled through the Java Community Process.[17] 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 lling of licens for specialized products such as the Java Enterpri System. Sun distinguishes 初一英语下册
between its Software Development Kit （SDK） and Runtime Environment (JRE） (a subt of the SDK)； the primary distinction involves the JRE’s lack of the compiler， utility programs, and header files。
On November 13, 2006, Sun relead much of Java as free and open source software， （FOSS), under the terms of the GNU General Public Licen （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。［18］
Sun's vice-president Rich Green said that Sun's ideal role with regards to Java was as an ”evangelist。”[19] Following Oracle Corporation's acquisition of Sun
Microsystems in 2009–2010, Oracle has described itlf as the ”steward of Java technology with a relentless commitment to fostering a community of participation and transparency”。[20] Java software runs on laptops to data centers， game consoles to scientific supercomputers. There are 930 million Java Runtime Environment downloads e
ach year and 3 billion mobile phones run Java。［21］ On April 2, 2010， James Gosling resigned from Oracle.［22］
Principles垠的意思
There were five primary goals in the creation of the Java language：［23］
1。 It should be ”simple, object—oriented and familiar”
2。 It should be ”robust and cure”
3。 It should be "architecture-neutral and portable"
4。 It should execute with ”high performance"
5. It should be "interpreted, threaded， and dynamic”
Versions
Main article: Java version history
Major relea versions of Java, along with their relea dates:
JDK 1。0 (January 23， 1996)
JDK 1.1 (February 19, 1997)
J2SE 1.2 (December 8, 1998）
J2SE 1.3 （May 8， 2000)
J2SE 1.4 （February 6， 2002）
J2EE 5.0 （September 30， 2004)
Java SE 6 （December 11, 2006)
Java SE 7 (July 28, 2011）
Practices
Java platform
汽车修复
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Main articles： 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 reprentation 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—urs commonly u a Java Runtime Environment （JRE） installed on their own machine for standalone Java applications， or in a Web browr复旦千分考 for Java applets。
