【正文】 ates a static method, which is associated only with the class and not with any specific instance of that class. Only static methods can be invoked without a reference to an object. Static methods cannot access any method variables that are not static. The keyword void indicates that the main method does not return any value to the caller. If a Java program is to exit with an error code, it must call () explicitly.The method name main is not a keyword in the Java language. It is simply the name of the method the Java launcher calls to pass control to the program. Java classes that run in managed environments such as applets and Enterprise JavaBean do not use or need a main() method. A java program may contain multiple classes that have main methods, which means that the VM needs to be explicitly told which class to launch from.The main method must accept an array of String objects. By convention, it is referenced as args although any other legal identifier name can be used. Since Java 5, the main method can also use variable arguments, in the form of public static void main(String... args), allowing the main method to be invoked with an arbitrary number of String arguments. The effect of this alternate declaration is semantically identical (the args parameter is still an array of String objects), but allows an alternative syntax for creating and passing the array.The Java launcher launches Java by loading a given class (specified on the mand line or as an attribute in a JAR) and starting its public static void main(String[]) method. Standalone programs must declare this method explicitly. The String[] args parameter is an array of String objects containing any arguments passed to the class. The parameters to main are often passed by means of a mand line.Criticism of JavaA number of criticisms have been leveled at Java programming language for various design choices in the language and platform. Such criticisms include the implementation of generics, the handling of unsigned numbers, the implementation of floatingpoint arithmetic, and security vulnerabilities.Class libraries Java Platform and Class libraries diagramJava libraries are the piled bytecodes of source code developed by the JRE implementor to support application development in Java. Examples of these libraries are: The core libraries, which include: Collection libraries that implement data structures such as lists, dictionaries, trees, sets, queues and doubleended queue, or stacksXML Processing (Parsing, Transforming, Validating) librariesSecurityInternationalization and localization librariesThe integration libraries, which allow the application writer to municate with external systems. These libraries include: The Java Database Connectivity (JDBC) API for database accessJava Naming and Directory Interface (JNDI) for lookup and discoveryRMI and CORBA for distributed application developmentJMX for managing and monitoring applicationsUser interface libraries, which include: The (heavyweight, or native) Abstract Window Toolkit (AWT), which provides GUI ponents, the means for laying out those ponents and the means for handling events from those ponentsThe (lightweight) Swing libraries, which are built on AWT but provide (nonnative) implementations of the AWT widgetryAPIs for audio capture, processing, and playbackA platform dependent implementation of Java Virtual Machine (JVM) that is the means by which the byte codes of the Java libraries and third party applications are executedPlugins, which enable applets to be run in Web browsersJava Web Start, which allows Java applications to be efficiently distributed to endusers across the InternetLicensing and documentation.DocumentationMain article: JavadocJavadoc is a prehensive documentation system, created by Sun Microsystems, used by many Java developers. It provides developers with an organized system for documenting their code. Javadoc ments have an extra asterisk at the beginning, . the tags are /** and */, whereas the normal multiline ment tags ments in Java and C are set off with /* and */.Sun has defined and supports four editions of Java targeting different application environments and segmented many of its APIs so that they belong to one of the platforms. The platforms are:Java Card for smartcards.、Java Platform, Micro Edition (Java ME) — targeting environments with limited resources、Java Platform, Standard Edition (Java SE) — targeting workstation environments、Java Platform, Enterprise Edition (Java EE) — targeting large distributed enterprise or Internet environments.The classes in the Java APIs are organized into separate groups called packages. Each package contains a set of related interfaces, classes and exceptions. Refer to the separate platforms for a description of the packages set of APIs is controlled by Sun Microsystems in cooperation with others through the Java Community Process program. Companies or individuals participating in this process can influence the design and development of the APIs. This process has been a subject of controversy. Sun also provided an edition called PersonalJava that has been superseded by later, standardsbased Java ME configurationprofile pairings.JSP Profile JSP (JavaServer Pages) is initiated by Sun Microsystems, Inc., with many panies to participate in the establishment of a dynamic web page technical standards. JSP technology somewhat similar to ASP technology, it is in the traditional HTML web page document (*. htm, *. html) to insert the Java programming paragraph (Scriptlet) and JSP tag (tag), thus JSP documents (*. jsp). Using JSP development of the Web application is crossplatform that can run on Linux, is also available for other operating systems. JSP technology to use the Java programming language prepared by the category of XML tags and scriptlets, to produce dynamic pages package processing logic. Page also visit by tags and scriptlets exist in th