Execution of Java programs

The beginning of the Java Platform and language was an internal project that sun began to study in December 1990. One of Sun's engineers, named Patrick Norton, was overwhelmed by the C and C language compilers he developed because the APIs were extremely difficult to use. Patrick decided to switch to next, and he was given the opportunity to study a project called the Stealth program.

?? " Stealth Program "later renamed" Green Plan ", jgosling (James Goslin) and Mack Chelindan also joined Patrick's working group. Together with several other engineers, they studied and developed new technologies in a small studio on Dune Road in California State Monropach, aiming to design the next generation of smart appliances, such as microwaves, and Sun expects future technology to be in the field of home appliances. The team initially considered using the C language, but many members, including Sun's chief scientist Bill Joy, found that C and the available APIs were problematic in some ways.
?? The Working Group uses an embedded type platform, which can be used with very limited resources. Many members found that C was too complex to be used incorrectly by many developers. They found that C lacked a garbage collection system, as well as portable security, distributed programming, and multithreading capabilities. Finally, they want a platform that is easily ported to a variety of devices.
?? Based on the funds available, Bill Joy decided to develop a new language for the C and Mesa languages, and in a report that Joey called "The Future," he suggested that Sun's engineers should develop an object-oriented environment based on C. Initially, Gosling tried to modify and extend the function of C, which he himself called the new language as C –, but later he gave up. He is about to create a new language, named "Oak" by him, named after the tree outside his office.
like many secret projects to develop new technologies, the Working Group worked night and night to1992summer, they were able to demonstrate part of the new platform, includingGreenOperating System,Oakprogramming languages, class libraries, and their hardware. The initial attempt was to target a classPDAdevice, which is namedSTAR7, this kind of equipment has brightGraphical Interfaceand is called"Duke"Intelligent Agents to help the user. 1992years AMonth3Day, the device was shown.
same year11months,Greenthe plan was converted into"FirstpersonCo., Ltd.", aSUNthe company's wholly owned subsidiary, the team was also rescheduled to Palo Alto. FirstpersonThe team was interested in building a highly interactive device when Time Warner released a request for a proposal for a TV set-top box (Request for Proposal),Firstpersonchanged their goal, as a response to the request for advice, proposed a set-top box platform. But the cable TV industry feelsFirstpersonthe platform gives the user too much control, soFirstpersonthe bid was defeatedSGI. With the3DOThe company's other deal on the set-top box was unsuccessful, as their platform could not produce any benefit in the television industry, and the company returnedSUNCompany.
until the second half of 1994, with the rapid development of the Internet and the rapid growth of global information Network, the first global information Network browser Mosaic was born; at this time, industry has a very urgent need for the language suitable for the heterogeneous environment in the network; Games Gosling decided to change the direction of the green plan, and they made a small transformation of oak, so that Java was born on March 23 in 1995! The birth of Java marks the beginning of the Internet era, it can be applied to the global Information network platform to write interactive and strong applet program, and the 1995 applet will undoubtedly give people infinite visual and mental vibration. But it is difficult to develop without a corresponding development library and Java-only language, so Sun released the JDK 1.0来 to help developers develop it on January 23 in 1996. The JDK consists of two parts: the runtime environment and the development tools. Following that, Sun released JDK 1.1 on February 18, 1997. JDK1.1 the biggest improvement over the older version is the introduction of the JIT (just-in-time) compiler, and the other improvement is AWT 1.1.

The origin of the Java name

　While some claim that Java is a combination of developer names:James Gosling(James·Gaussian forest)Arthur Van Hoff(Arthur·where·Hof)Andy Bechtolsheim(Andy·Bectock), or"Just another Vague acronym"(just another vague abbreviation). There is also a more credible argument is that the name is out of the love of coffee, so toJavacoffee to name it. The first four bytes of a class file, if read in hexadecimal, areCA FE BA be, it will spell two words"CAFE BABE"(coffee baby).
1994yearsTenmonths,HotJavaand theJavaPlatform for the company's high-level demonstration. 1994years,Java 1.0aThe version is available for download, butJavaand theHotJavathe first public release of the browser was1995years5Month atDaySunworldat the conference. SUNscientific guidance of the company John·Gage ProclamationJavatechnology. This release is with Netscape's executive vice President Mark·Anderson's amazing release, announced that Netscape will include in its browser theJavathe support. 1996years1month, the company set up the SunJavaBusiness Group, specialized in developingJavatechnology.

Execution flow of Java programs

   java is the process of compiling the  java source code into code that works on the local platform. First of all, write java   source program , java  compiler will java  source program compiled into executable class file, re-passed jvm  < Span style= "font-family: Arial" > Virtual machine converts a class file to a code that conforms to the current platform characteristics ,    again Runtime Envionment (interpreter) explains the run.   using java  on a single machine The program written and translated does not need to be re-translated can be executed on another machine. The JAVA source program can be edited with any editing program, then java  as suffix.

　　A Java Virtual machine (JVM) is an interpretation device that translates class files into Java programs that are applied on different platforms. A Java Virtual machine (JVM) is an imaginary computer that can run Java code. As long as the interpreter is ported to a specific computer according to the JVM specification description, any compiled Java code can be guaranteed to run on that system. In our view, Java Virtual machine is to make the class file can run on different platforms Java bytecode interpreter, Java Virtual machine has many kinds, such as can be applied in Windows,linux,unix, such as the operating platform, we can use virtual machine to achieve "one place to write, run everywhere "theJVM is a virtual machine that, structurally, is similar to a real computer, and its purpose is to enable an actual machine to run a JAVA bytecode program." java bytecode is a Java source program compiled by the program, it cannot be directly executed by the computer, but it can be executed by all Java virtual machines. This is why the Java bytecode program can be ported on the network.

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Execution of Java programs