Java
1Java
2Java
[′jäv·ə]Java
(programming, language, portability)Java first became popular by being the earliest portable dynamic client-side content for the World-Wide Web in the form of platform-independent Java "applets". In the late 1990's and into the 2000's it has also become very popular on the server side, where an entire set of APIs defines the J2EE.
Java is both a set of public specifications (controlled by Sun Microsystems through the JCP) and a series of implementations of those specifications.
Java is syntactially similar to C++ without user-definable operator overloading, (though it does have method overloading), without multiple inheritance, and extensive automatic coercions. It has automatic garbage collection. Java extends C++'s object-oriented facilities with those of Objective C for dynamic method resolution.
Whereas programs in C++ and similar languages are compiled and linked to platform-specific binary executables, Java programs are typically compiled to portable architecture-neutral bytecode or ".class" files, which are run using a Java Virtual Machine. The JVM is also called an interpreter, though it is more correct to say that it uses Just-In-Time Compilation to convert the bytecode into native machine code, yielding greater efficiency than most interpreted languages, rivalling C++ for many long-running, non-GUI applications. The run-time system is typically written in POSIX-compliant ANSI C or C++. Some implementations allow Java class files to be translated into native machine code during or after compilation.
The Java compiler and linker both enforce strong type checking - procedures must be explicitly typed. Java supports the creation of virus-free, tamper-free systems with authentication based on public-key encryption.
Java has an extensive library of routines for all kinds of programming tasks, rivalling that of other languages.
For example, the "java.net} package supports TCP/IP protocols like HTTP and FTP. Java applications can access objects across the Internet via URLs almost as easily as on the local file system. There are also capabilities for several types of distributed applications.
The Java GUI libraries provide portable interfaces. For example, there is an abstract Window class and implementations of it for Unix, Microsoft Windows and the Macintosh. The "java.awt" and "javax.swing" classes can be used either in Web-based "Applets" or in client-side or "desktop" applications.
There are also packages for developing XML applications, web services, servlets and other web applications, security, date and time calculations and I/O formatting, database (JDBC), and many others.
Java is not directly related to JavaScript despite the name.
http://java.sun.com/.
Usenet newsgroup: news:comp.lang.java.
Java
An object-oriented programming language from Oracle that is platform independent. Developed by Sun in the early 1990s (Oracle acquired Sun in 2010), and modeled after C++, Java was originally designed for embedded applications in set-top boxes and other consumer electronics. Java ignited a revolution when Sun transitioned it to the Web in 1994. It is used in desktop computers, servers, mobile devices and Blu-ray players with more than three billion installations as of 2020.Applet, App and Servlet
When a Java program is launched from a Web page, the program is called a Java "applet." When run without the Web browser on a user's machine, it is a Java "application." When running in a Web server, it is a Java "servlet."
Write Once-Run Anywhere
Java embodies the "write once-run anywhere" model. For example, a Java program can be moved from a Unix server to a Windows server with minimal modification most of the time. This is accomplished because Java source code is first compiled into an intermediate "bytecode" language. In order to run the bytecode, it is either compiled into machine code and then run or executed a line at a time via the Java interpreter, a runtime engine known as the "Java Virtual Machine" (JVM). There are JVMs for all major hardware platforms, which is what makes Java cross platform. When users are notified to update Java in their computers, they are updating the runtime engine (see Java Virtual Machine). See Java platform, servlet, JSP, Jini, garbage collection, CaffeineMark and caffeine based.
Java vs. JavaScript
Although they share a similar-sounding name, Java is not JavaScript (for the difference, see JavaScript).
The following Java example of changing Fahrenheit to Celsius is rather wordy compared to the C example in this encyclopedia. Java is designed for GUI-based applications, and several extra lines of code are necessary here to allow input from a terminal.
import java.io.*;
class Convert {
public static void main(String[]args)
throws IOException {
float fahr;
StreamTokenizer in=new
StreamTokenizer
(new InputStreamReader(System.in));
System.out.print("Enter Fahrenheit ");
in.nextToken();
fahr = (float) in.nval;
System.out.println ("Celsius is " +
(fahr-32)*5/9);
}
}
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| Java Uses an Intermediate Language |
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| Java source code is compiled into an intermediate language called "bytecode." The bytecode can be run in any hardware that has a Java Virtual Machine (JVM) for that machine platform. Thus, the "write once-run anywhere" concept. |
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| Java Runs on Clients and Servers |
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| When a Java program is called by a Web page from the client machine, it is dubbed an "applet." When it runs on the server, it is a "servlet." When running stand-alone in a user's computer, it is a Java "application." |
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Java
an island in the Malay Archipelago, in the Greater Sunda Islands. The main economic region of Indonesia, Java has an area of 126,500 sq km and a population of about 83 million (1975).
Java, which extends west to east for 1,050 km, is washed in the south by the Indian Ocean, in the north by the Java Sea, in the west by the Sunda Strait, and in the east by the Bali Strait. In the south the shores are mostly high and steep; in the north they are low and often swampy.
About half of Java is covered by mountains. The island is crossed by a mountain chain, among the higher peaks of which are more than 100 volcanoes, including about 30 active ones. More than ten volcanoes exceed 3,000 m in elevation; the tallest, Semeru, has an elevation of 3,676 m. In the north and south are hills and low mountains composed principally of sandstones and limestones; karst has developed extensively. Alluvial plains lie in sections along the coasts and river valleys. Java has deposits of petroleum along the northern coast, sulfur in the volcanic regions, and manganese ore in the south; in addition, there are deposits of phosphorites and gold.
Java has a subequatorial monsoon climate. Along the coasts the air temperature is 26°–27°C throughout the year; it drops to approximately 18°C at 1,500 m and about 9°C at 3,000 m. The temperature may vary by as much as 10°–15°C daily. Annual precipitation is 1,000–2,000 mm in the plains and 3,000–5,000 mm in the mountains, exceeding 6,000 mm on some peaks; most of the precipitation falls between October and May. The western half of Java is wetter than the eastern half. The rivers have abundant water, especially in the rainy season, and are used for irrigation.
Podzolized lateritic soils, mountain-forest red soils, and alluvial soils predominate in the river valleys. Cultivated landscapes prevail in the plains and foothills. About one-fourth of Java is forested. In the western mountains there are vast equatorial rain forests, about 50 m in height, that have multiple strata; they are distinguished by an enormous variety of species. In the east are monsoon deciduous forests and savanna-type thin forests. At elevations of more than 1,500 m are usually found forests that include laurels, magnolias, oaks, and chestnuts. Mountain peaks are covered by thickets of low shrubs and by meadows. There are mangrove forests in some sections along the coast.
The forests are inhabited by apes, deer, and wild boars; rhinoceroses, tigers, leopards, and bantengs are also found. Java has a great variety of bird, reptile, and insect life. The flora and fauna of Java are protected in the natural parks of Baluran, Banjuwangi Selatan, Pulau-Panaitan, and Ujung-Kulon. The botanical garden in the city of Bogor is known throughout the world. Java’s largest cities are Jakarta (the capital of Indonesia), Bandung, Jogjakarta, Semarang, and Surabaya.
The economy, history, and art of Java are discussed in INDONESIA.
N. V. ALEKSANDROVSKAIA