Characteristics of Java: 1. Object-oriented; it has good support for classes, objects, inheritance, encapsulation, polymorphism, interfaces, packages, etc. in objects. 2. Platform independence; after the introduction of the virtual machine, the Java language does not need to be recompiled to run on different platforms. 3. Simplicity. 4. Interpretation and execution; when the program is run on the Java platform, it will be compiled into a bytecode file, and then it can be run on an operating system with a Java environment. 5. Support multi-threading and provide synchronization mechanism between multi-threads; 6. Distribution; 7. Robustness; 8. High performance; 9. Security.
The operating environment of this tutorial: windows7 system, java8 version, DELL G3 computer.
What is Java language
Simply put, Java is an object-oriented programming language launched by Sun Microsystems in 1995 . In 2010, Oracle acquired Sun Microsystems, and Oracle was subsequently responsible for Java maintenance and version upgrades.
In fact, Java is still a platform. The Java platform consists of the Java Virtual Machine (JVM) and the Java Application Programming Interface (API). The Java Application Programming Interface provides a standard interface independent of the operating system, which can be divided into basic parts and extended parts. After a Java platform is installed on the hardware or operating system platform, Java applications can run.
The Java platform has been embedded in almost all operating systems. In this way, the Java program is compiled only once and can be run on various systems. The Java Application Programming Interface has evolved from version 1.1x to version 1.2.
Characteristics of Java language
The style of Java language is very similar to C language and C language. It is a pure object-oriented language. It inherits the core object-oriented technology of C language, but abandons some shortcomings of C, such as pointers that easily cause errors and multiple inheritance. It also adds a garbage collection mechanism to release unused memory space and solve the problem. The trouble of managing memory space.
The Java language is a distributed object-oriented language with many features such as object-oriented, platform-independent, simplicity, interpretation and execution, multi-threading, security, etc. These features are introduced one by one below.
1. Object-oriented
Java is an object-oriented language. It has a good understanding of classes, objects, inheritance, encapsulation, polymorphism, interfaces, and packages in objects. All have good support. For simplicity, Java only supports single inheritance between classes, but multiple inheritance can be implemented using interfaces. To develop programs using Java language, you need to adopt object-oriented thinking to design programs and write code.
2. Platform independence
The specific manifestation of platform independence is that Java is a "Write Once, Run any Where" language , so programs written in Java language have good portability, and it is Java's virtual machine mechanism that ensures this. After the introduction of virtual machines, the Java language does not need to be recompiled to run on different platforms.
The Java language uses the Java virtual machine mechanism to shield relevant information about specific platforms, so that programs compiled in the Java language only need to generate target code on the virtual machine and can run on multiple platforms without modification.
3. Simplicity
The syntax of Java language is very similar to C language and C language, making it easy for many programmers to learn. For Java, it abandons many features that are difficult to understand in C, such as operator overloading and multiple inheritance. Moreover, the Java language does not use pointers and adds a garbage collection mechanism, which solves the problem that programmers need to manage memory. Makes programming easier.
4. Explanation and execution
When a Java program is run on the Java platform, it will be compiled into a bytecode file, which can then be run on an operating system with a Java environment. When running the file, the Java interpreter interprets and executes these bytecodes, and the classes that need to be added during the execution are loaded into the running environment during the connection phase.
5. Multi-threading
The Java language is multi-threaded, which is also a major feature of the Java language. It must be created by the Thread class and its subclasses . Java supports multiple threads executing simultaneously and provides a synchronization mechanism between multiple threads. Each thread has its own run() method, and the method to be executed is written in the run() method body.
6. Distributed
Java language supports the development of Internet applications. Among the basic application programming interfaces of Java, there is a network application programming interface, which provides network Class libraries for application programming, including URL, URLConnection, Socket, etc. Java's RIM mechanism is also an important means of developing distributed applications.
7. Robustness
Механизм строгого типа Java, обработка исключений, механизм сборки мусора и т. д. — все это важные гарантии надежности Java. Отказ от указателей — важное достижение в Java. Кроме того, механизм исключений Java также является важным проявлением надежности.
8. Высокая производительность
Высокая производительность Java в основном сравнивается с другими языками сценариев высокого уровня. скорость также становится все выше и выше.
9.Безопасность
Java обычно используется в сетевой среде.По этой причине Java предоставляет механизм безопасности для предотвращения атак вредоносного кода. В дополнение ко многим функциям безопасности языка Java, Java также добавляет механизм предотвращения безопасности к классам, загружаемым через сеть, выделяет различные пространства имен для предотвращения замены локальных классов с тем же именем и включает механизм управления безопасностью.
Многие особенности языка Java позволяют ему занять большую долю рынка среди многих языков программирования.Поддержка языка Java объектов и мощный API делают работу по программированию проще и быстрее, значительно сокращая время, необходимое для программирования. затраты на разработку. Принцип Java ?напиши один раз, выполняй где угодно? — одно из его преимуществ, которое привлекает множество предприятий и программистов.
Расширить знания:
По сфере применения Java можно разделить на 3 системы, а именно Java SE, Java EE и Java ME. Эти три системы кратко представлены ниже.
1. Java SE
Java SE (Java Platform Standard Edition, Java Platform Standard Edition), ранее известная как J2SE, позволяет разрабатывать и развертывать на настольных компьютерах, серверах, Приложения Java, используемые во встроенных средах и средах реального времени. Java SE содержит классы, которые поддерживают разработку веб-сервисов Java и обеспечивают основу для Java EE, такие как основа языка Java, операции JDBC, операции ввода-вывода, сетевая связь и многопоточные технологии. На рисунке 1 показана архитектура Java SE.
#Java EE
Java EE (Java Platform Enterprise Edition, Java Platform Enterprise Edition) ранее назывался J2EE. Версия Enterprise Edition помогает разрабатывать и развертывать серверные Java-приложения, которые являются переносимыми, надежными, масштабируемыми и безопасными. Java EE построен на Java SE и предоставляет веб-службы, модели компонентов, API-интерфейсы управления и связи, которые можно использовать для реализации сервис-ориентированной архитектуры (SOA) корпоративного класса и приложений Web 2.0.
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