Introduction to Java language (power node arrangement)

Java is anobject-orientedprogramming language, which not only absorbs the various advantages of the C++ language, but also abandons many incomprehensible features in C++Inheritance, pointers and other concepts, so the Java language has two characteristics: powerful and simple to use. Let’s share with you the Introduction to the Java language through this article. Friends who are interested should take a look.

Java IntroductionJava is a Java object-oriented program launched by Sun Microsystems (now acquired by Oracle) in May 1995 A general term for programming languages ​​and Java platforms. It was jointly developed by James Gosling and colleagues and officially launched in 1995. According to Oracle's official data index, there are currently hundreds of millions of systems around the world developed using Java.

Java is an object-oriented programming language. It not only absorbs the various advantages of the C++ language, but also abandons the difficult-to-understand concepts such as multiple inheritance and pointers in C++. Therefore, the Java language is powerful and easy to use. Two characteristics. As a representative of the

object-oriented programming language, the Java language perfectly implements the object-oriented theory and allows programmers to perform complex programming with an elegant way of thinking.
Java has the characteristics of simplicity, object-oriented, distributed, robustness,

, platform independence and portability, multi-threading, and dynamics. Java can write desktop applications, Web applications, distributed systems and embedded system applications, etc.

 JavaSE (JSE) (Java Platform Standard Edition, Java Platform Standard Edition, the abbreviation of the old version is J2SE)

 JavaEE (JEE) (Java Platform, Enterprise Edition, Java Platform Enterprise Edition, the old version abbreviation is J2EE)

 JavaME (JME) (Java Platform Micro Edition, Java Platform Micro Edition, the old version abbreviation is J2ME )

In June 2005, the JavaOne conference was held, and SUN released Java SE 6. At this time, various versions of Java had been renamed to remove the number "2": J2EE was renamed Java EE, J2SE was renamed Java SE, and J2ME was renamed Java ME.

Main Features

The syntax of the Java language is the same as

is very close to the C++ language, making it easy for most C or C++ programmers to learn and use. On the other hand, Java discards those features in C++ that are rarely used, difficult to understand, and confusing, such as operatoroverloading, multiple inheritance, and automatic coercion. Type conversion. In particular, the Java language does not use pointers, but references. It also provides automatic waste collection so that programmers don't have to worry about memory management.

The Java language provides primitives such as classes, interfaces, and inheritance. For simplicity, it only supports single inheritance between classes. However, it supports multiple inheritance between interfaces and supports the implementation mechanism between classes and interfaces (the keyword is implements). The Java language fully supports dynamic binding, while the C++ language only uses dynamic binding for virtual functions. In short, the Java language is a pure object-oriented programming language.

The Java language supports the development of Internet applications. There is a network application programming interface (Java net) in the basic Java application programming interface, which provides a network application Programming class libraries, including URL, URLConnection, Socket, ServerSocket, etc. Java's RMI (Remote Method Activation) mechanism is also an important means of developing distributed applications.

Java’s strong typing mechanism, exception handling, automatic garbage collection, etc. are important guarantees for the robustness of Java programs. Discarding pointers is a smart choice for Java. Java's security checking mechanism makes Java more robust.

Java is usually used in a network environment. For this reason, Java provides a security mechanism to prevent malicious code attacks. In addition to the many security features of the Java language, Java has a security prevention mechanism (class ClassLoader) for classes downloaded through the network, such as allocating different name spaces to prevent replacement of local classes with the same name, byte code inspection, and providing

The mechanism (class SecurityManager) allows Java applications to set security sentries.

Java programs (files with the suffix .java) are compiled into an architecture-neutral bytecode format (files with the suffix .class) on the Java platform, and can then be run on any system that implements this Java platform (windows , mac, linux, etc.) to run, truly realizing the effect of compiling in multiple places at once. This approach is suitable for heterogeneous network environments and software distribution.

Java language is interpreted:

As mentioned before, Java programs are compiled into bytecode format on the Java platform, and then can be Runs on any system implementing this Java platform. At runtime, the Java interpreter in the Java platform interprets and executes these bytecodes, and the classes required during the execution are loaded into the running environment during the connection phase. 

Java is high-performance:

Compared with those interpreted high-level scripting languages, Java is indeed high-performance. In fact, the running speed of Java is getting closer and closer to that of C++ with the development of JIT (Just-In-Time) compiler technology. 

The Java language is multi-threaded:

In the Java language, a thread is a special object that must be created by the Thread class or its subclasses. (grandchild) class to create. There are usually two ways to create a thread: first, use the constructor of type Thread(Runnable) to wrap an object that implements the Runnable interface into a thread; second, derive a subclass from the Thread class and override run Method, the object created using this subclass is a thread. It is worth noting that the Thread class has implemented the Runnable interface, so any thread has its run method, and the run method contains the code to be run by the thread. The activity of a thread is controlled by a set of methods. The Java language supports the simultaneous execution of multiple threads and provides a synchronization mechanism between multiple threads (the keyword is synchronized).

The Java language is dynamic:

One of the design goals of the Java language is to adapt to dynamically changing environments. The classes required by Java programs can be dynamically loaded into the running environment, or the required classes can be loaded through the network. This also facilitates software upgrades. In addition, classes in Java have a run-time representation and can perform run-time type checking.

Development History

 On May 23, 1995, the Java language was born

 1996 In April 1996, the first JDK-JDK1.0 was born

 In April 1996, the 10 major operating system vendors stated that they would embed JAVA technology in their products

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