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Java Virtual Machine
A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describes what is required in a JVM implementation. Having a specification ensures interoperability of Java programs across different implementations so that program authors using the Java Development Kit (JDK) need not worry about idiosyncrasies of the underlying hardware platform. The JVM reference implementation is developed by the OpenJDK project as open source code and includes a JIT compiler called HotSpot. The commercially supported Java releases available from Oracle are based on the OpenJDK runtime. Eclipse OpenJ9 is another open source JVM for OpenJDK. JVM specification The Java virtual machine is an abstract (virtual) computer defined by a specification. It is a part of java runtime environment. The garbage-collection algorit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Java Bytecode
In computing, Java bytecode is the bytecode-structured instruction set of the Java virtual machine (JVM), a virtual machine that enables a computer to run programs written in the Java programming language and several other programming languages, see List of JVM languages. Relation to Java A Java programmer does not need to be aware of or understand Java bytecode at all. However, as suggested in the IBM developerWorks journal, "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 assembly helps the C or C++ programmer." Instruction set architecture The JVM is both a stack machine and a register machine. Each frame for a method call has an "operand stack" and an array of "local variables". The operand stack is used for operands to computations and for receiving the return value of a called method, while local variables serve the same purpose as registers and are also used to pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Sun Microsystems
Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the Network File System (NFS), and SPARC microprocessors. Sun contributed significantly to the evolution of several key computing technologies, among them Unix, RISC processors, thin client computing, and virtualized computing. Notable Sun acquisitions include Cray Business Systems Division, Storagetek, and ''Innotek GmbH'', creators of VirtualBox. Sun was founded on February 24, 1982. At its height, the Sun headquarters were in Santa Clara, California (part of Silicon Valley), on the former west campus of the Agnews Developmental Center. Sun products included computer servers and workstations built on its own RISC-based SPARC processor architecture, as well as on x86-based AMD Opteron and Intel Xeon processors. Sun also dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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HotSpot (virtual Machine)
HotSpot, released as Java HotSpot Performance Engine, is a Java virtual machine for desktop and server computers, developed by Sun Microsystems and now maintained and distributed by Oracle Corporation. It features improved performance via methods such as just-in-time compilation and adaptive optimization. History The Java HotSpot Performance Engine was released on April 27, 1999, built on technologies from an implementation of the programming language Smalltalk named Strongtalk, originally developed by Longview Technologies, which traded as Animorphic. The Longview virtual machine was based on the Self virtual machine, with an interpreter replacing the fast-and-dumb first compiler. When Sun cancelled the Self project, two key people, Urs Hölzle and Lars Bak left Sun to start Longview. In 1997, Sun Microsystems purchased Animorphic. Shortly after acquiring Animorphic, Sun decided to write a new just-in-time (JIT) compiler for the Java virtual machine. This new compiler w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Sign-extended
Sign extension (abbreviated as sext) is the operation, in computer arithmetic, of increasing the number of bits of a binary number while preserving the number's sign (positive/negative) and value. This is done by appending digits to the most significant side of the number, following a procedure dependent on the particular signed number representation used. For example, if six bits are used to represent the number "00 1010" (decimal positive 10) and the sign extend operation increases the word length to 16 bits, then the new representation is simply "0000 0000 0000 1010". Thus, both the value and the fact that the value was positive are maintained. If ten bits are used to represent the value "11 1111 0001" (decimal negative 15) using two's complement, and this is sign extended to 16 bits, the new representation is "1111 1111 1111 0001". Thus, by padding the left side with ones, the negative sign and the value of the original number are maintained. In the Intel x86 instruction se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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64-bit Computing
In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit CPUs and ALUs are those that are based on processor registers, address buses, or data buses of that size. A computer that uses such a processor is a 64-bit computer. From the software perspective, 64-bit computing means the use of machine code with 64-bit virtual memory addresses. However, not all 64-bit instruction sets support full 64-bit virtual memory addresses; x86-64 and ARMv8, for example, support only 48 bits of virtual address, with the remaining 16 bits of the virtual address required to be all 0's or all 1's, and several 64-bit instruction sets support fewer than 64 bits of physical memory address. The term ''64-bit'' also describes a generation of computers in which 64-bit processors are the norm. 64 bits is a word size that defines certain classes of computer architecture, buses, memory, and CPUs and, by extension, the software th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Integer
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language of mathematics, the set of integers is often denoted by the boldface or blackboard bold \mathbb. The set of natural numbers \mathbb is a subset of \mathbb, which in turn is a subset of the set of all rational numbers \mathbb, itself a subset of the real numbers \mathbb. Like the natural numbers, \mathbb is countably infinite. An integer may be regarded as a real number that can be written without a fractional component. For example, 21, 4, 0, and −2048 are integers, while 9.75, , and are not. The integers form the smallest group and the smallest ring containing the natural numbers. In algebraic number theory, the integers are sometimes qualified as rational integers to distinguish them from the more general algebraic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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File Format
A file format is a Computer standard, standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary format, proprietary or open format, free. Some file formats are designed for very particular types of data: Portable Network Graphics, PNG files, for example, store Raster graphics, bitmapped Graphics file format, images using lossless data compression. Other file formats, however, are designed for storage of several different types of data: the Ogg format can act as a container format (digital), container for different types of multimedia including any combination of sound, audio and video, with or without text (such as subtitles), and metadata. A text file can contain any stream of characters, including possible control characters, and is encoded in one of various Character encoding, character encoding schemes. Some file formats, such as HTML, sca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Class (computer Programming)
In object-oriented programming, a class is an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods). In many languages, the class name is used as the name for the class (the template itself), the name for the default constructor of the class (a subroutine that creates objects), and as the type of objects generated by instantiating the class; these distinct concepts are easily conflated. Although, to the point of conflation, one could argue that is a feature inherent in a language because of its polymorphic nature and why these languages are so powerful, dynamic and adaptable for use compared to languages without polymorphism present. Thus they can model dynamic systems (i.e. the real world, machine learning, AI) more easily. When an object is created by a constructor of the class, the resulting object is called an instance of the class, and the member variable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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JRockit
JRockit was a proprietary Java virtual machine (JVM) originally developed by Appeal Virtual Machines, acquired by BEA Systems in 2002, and became part of Oracle Fusion Middleware as part of acquisition of BEA Systems in 2008. The JRockit code base was discontinued by Oracle, with some features being integrated into the HotSpot virtual machine as part of the mainline development of the Java platform. JRockit only ever supported Java 6, which is now considered an obsolete release. History Following the finalization of the acquisition of Sun Microsystems, Oracle announced in JavaOne 2010 that the best features of JRockit would be implemented in OpenJDK. In May 2011, Oracle announced that JRockit has become free, and confirmed the plan to port JRockit features on OpenJDK OpenJDK (Open Java Development Kit) is a free and open-source implementation of the Java Platform, Standard Edition (Java SE). It is the result of an effort Sun Microsystems began in 2006. The implementation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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BEA Systems
BEA Systems, Inc. was a company that specialized in enterprise infrastructure software products which was wholly acquired by Oracle Corporation on April 29, 2008. History BEA began as a software company, founded in 1995 and headquartered in San Jose, California. It grew to have 78 offices worldwide at the time of its acquisition by Oracle. The company's name is an initialism of the first names of the company's three founders: Bill Coleman, Ed Scott, and Alfred Chuang. All were former employees of Sun Microsystems, and launched the business in 1995 by acquiring Information Management and Independence Technologies. These firms were the largest resellers of ''Tuxedo'', a distributed transaction management system sold by Novell. BEA soon acquired the Tuxedo product itself, and went on to acquire other middleware companies and products. In 1998, BEA acquired the San Francisco start-up WebLogic, which had built the first standards-based Java application server. WebLogic's appl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Class (file Format)
A Java class file is a file (with the filename extension) containing Java bytecode that can be executed on the Java Virtual Machine (JVM). A Java class file is usually produced by a Java compiler from Java programming language source files ( files) containing Java classes (alternatively, other JVM languages can also be used to create class files). If a source file has more than one class, each class is compiled into a separate class file. JVMs are available for many platforms, and a class file compiled on one platform will execute on a JVM of another platform. This makes Java applications platform-independent. History On 11 December 2006, the class file format was modified under Java Specification Request (JSR) 202. File layout and structure Sections There are 10 basic sections to the Java class file structure: * Magic Number: 0xCAFEBABE * Version of Class File Format: the minor and major versions of the class file * Constant Pool: Pool of constants for the class * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Java Community Process
The Java Community Process (JCP), established in 1998, is a formalized mechanism that allows interested parties to develop standard technical specifications for Java technology. Anyone can become a JCP Member by filling a form available at thJCP website JCP membership for organizations and commercial entities requires annual fees – but is free for individuals. The JCP involves the use of Java Specification Requests (JSRs) – the formal documents that describe proposed specifications and technologies for adding to the Java platform. Formal public reviews of JSRs take place before a JSR becomes ''final'' and the JCP Executive Committee votes on it. A final JSR provides a ''reference implementation'' that is a free implementation of the technology in source code form and a '' Technology Compatibility Kit'' to verify the API specification. A JSR describes the JCP itself. , JSR 387 describes the current version (2.11) of the JCP. List of JSRs There are hundreds of JSRs. Some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |