Java is a legend in the development of computer software in the past ten years. Its position in the hearts of many developers can be described as "hard to put it down". Still going strong.
Since its first release, Java has leapt to the forefront of Internet programming. Each subsequent release has further cemented that position. Today, Java remains the best choice for developing Web-based applications. In addition, Java is also the driving force behind the smartphone revolution, and Android programming uses the Java language.
What is the Java language
Simply put, Java is an object-oriented programming language launched in 1995 by Sun Microsystems. In 2010, Oracle Corporation acquired Sun Microsystems, after which Oracle Corporation was responsible for Java maintenance and version upgrades.
In fact, Java is still a platform. The Java platform consists of a Java Virtual Machine (Java Virtual Machine, JVM) and a Java Application Programming Interface (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 installing a Java platform on a hardware or operating system platform, Java applications can run.
The Java platform is embedded in almost all operating systems. In this way, a Java program can be compiled only once and run on various systems. The Java API has evolved from version 1.1x to version 1.2. The commonly used Java platform is based on Java 8 and the latest version is Java 20.
Since the development of Java, it has tried to make it omnipotent. In the world programming language rankings, although Java's ranking has risen and fallen in recent years, it has always been in the top five, and the gap with the top few is not big, and it is nearly 5 percentage points behind C#.
So why do many programming languages learn Java?
- Wide application: Java is a widely used programming language, which is used to develop various types of applications, including enterprise applications, web applications, mobile applications, desktop applications, big data processing, etc. Many large enterprises and organizations use Java, so learning Java can provide you with wider employment opportunities and career development space.
- Cross-platform: Java is a cross-platform programming language, which means that Java code can run on different operating systems such as Windows, Mac, Linux, etc. This is due to the Java Virtual Machine (JVM), which provides an execution environment independent of the underlying operating system, making Java applications highly portable.
- Object-Oriented Programming: Java is an object-oriented programming language that supports core object-oriented concepts like encapsulation, inheritance, and polymorphism. Through object-oriented programming, the code can be better organized and managed, and the reusability and maintainability of the code can be improved.
- Large Ecosystem: Java has a large and active developer community and ecosystem. This means that a large number of development tools, libraries, frameworks and resources are readily available to speed up development and increase efficiency. For example, the Spring framework, the Hibernate ORM framework, and the Apache Hadoop big data processing framework are all popular tools and frameworks in the Java ecosystem.
- Powerful library and API support: Java provides a wealth of standard libraries and APIs, covering various functions and fields, such as network programming, database access, graphical user interface, multi-thread processing, etc. These libraries and APIs can quickly realize various functions and reduce the development workload.
- Security: Java focuses on security and provides many security features at the language and platform levels. For example, Java's security model protects the system from malicious code through bytecode verification and security sandbox mechanisms. This makes Java ideal for developing applications with high security requirements.
- Slow Learning Curve: Compared to some other programming languages, Java has a relatively gentle learning curve. It has clear syntax rules, rich documentation and tutorial resources, and Java is also taught in many school and university computer science courses, which makes it relatively easy for beginners to get started and build a solid programming foundation.
- Employment and career development opportunities: Since Java is widely used in enterprise-level application development and large-scale system development, mastering Java programming skills can provide a wealth of employment opportunities and career development paths. Many companies require candidates to have Java programming experience and knowledge when recruiting.
- Multi-field support: Java is not only suitable for back-end development, but also for Android application development, big data processing, scientific computing, artificial intelligence and other fields. This makes Java a versatile programming language that can be useful in different fields and industries.
- Mature and stable: Java is a mature programming language that has been developed and verified for a long time. It has a stable syntax and functionality, and there is a strong development community continuously improving and enhancing the Java ecosystem. This means that Java can be trusted to build reliable and scalable applications.
There are many beginners who may not be able to distinguish the three systems of Java, namely Java SE, Java EE and Java ME. The three systems are briefly introduced below.
1. Java SE
Java SE (Java Platform Standard Edition, Java Platform Standard Edition), formerly known as J2SE, allows the development and deployment of Java applications for use in desktops, servers, embedded environments, and real-time environments. Java SE includes classes that support the development of Java Web services and provides the foundation for Java EE, such as the Java language foundation, JDBC operations, I/O operations, network communication, and multithreading technologies. The following figure shows the architecture of Java SE.
2. Java EE
Java EE (Java Platform Enterprise Edition, Java Platform Enterprise Edition) was formerly known as J2EE. The Enterprise Edition helps develop and deploy portable, robust, scalable, and secure server-side Java applications. Java EE builds on Java SE and provides Web services, component models, management and communication APIs that can be used to implement enterprise-class Service Oriented Architecture (Service Oriented Architecture, SOA) and Web 2.0 applications.
3.Java ME
Java ME (Java Platform Micro Edition, Java Platform Micro Edition) was formerly known as J2ME, also known as K-JAVA. Java ME provides a robust and flexible environment for applications running on mobile and embedded devices such as cell phones, PDAs, TV set-top boxes, and printers.
Java ME includes a flexible user interface, a robust security model, a rich set of built-in networking protocols, and support for dynamically downloaded networked and offline applications. Applications based on the Java ME specification can be written once for many devices and can take advantage of each device's native capabilities.
Features of the Java language
The style of the Java language is very similar to the C language and the C++ language. It is a pure object-oriented language. It inherits the core technology of the C++ language object-oriented technology, but abandons some of the shortcomings of C++, such as error-prone pointers and multiple inheritance. etc. At the same time, a garbage collection mechanism is added to release unused memory space, which solves the trouble of managing memory space.
The Java language is a distributed object-oriented language, which has many characteristics such as object-oriented, platform-independent, simplicity, interpretation and execution, multi-threading, security, etc. The following will introduce these characteristics one by one.
1. Object Oriented
Java is an object-oriented language, which has good support for classes, objects, inheritance, encapsulation, polymorphism, interfaces, packages, etc. in objects. For simplicity, Java only supports single inheritance between classes, but multiple inheritance can be achieved using interfaces. Using the Java language to develop programs requires the use of object-oriented thinking to design programs and write codes.
2. Platform independence
The specific manifestation of platform independence is that Java is a "write once, run anywhere (Write Once, Run any Where)" language, so programs written in Java language have good portability, and it is precisely Java's virtual machine mechanism. After the introduction of the virtual machine, 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 the relevant information of the specific platform, so that the program compiled by the Java language only needs to generate the object code on the virtual machine, and can run on various platforms without modification.
3. Simplicity
The syntax of Java language is very similar to C language and C++ language, which makes it easy for many programmers to learn. For Java, it discards many features that are difficult to understand in C++, such as operator overloading and multiple inheritance, and the Java language does not use pointers, and adds a garbage collection mechanism, which solves the problem that programmers need to manage memory. Make programming easier.
4. Explain execution
When a Java program runs 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 process are loaded into the running environment during the connection phase.
5. Multithreading
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 simultaneous execution of multiple threads and provides a synchronization mechanism between multiple threads. Any thread has its own run() method, and the method to be executed is written in the body of the run() method.
6. Distributed
The Java language supports the development of Internet applications. Among the basic APIs of Java, there is a network application programming interface, which provides a class library for network application programming, including URL, URLConnection, and Socket. Java's RIM mechanism is also an important means of developing distributed applications.
7. Robustness
Java's strong type mechanism, exception handling, garbage collection mechanism, etc. are all important guarantees for the robustness of Java. The discarding of pointers is a big step forward for Java. In addition, Java's exception mechanism is also a great embodiment of robustness.
8. High performance
Java's high performance is mainly relative to other high-level scripting languages. With the development of JIT (Just in Time), Java's running speed is getting higher and higher.
9. Security
Java is usually used in the network environment, for this reason, Java provides a security mechanism to prevent malicious code attacks. In addition to many security features of the Java language, Java also adds a security mechanism to classes downloaded through the network, allocates different namespaces to prevent local classes of the same name from being replaced, and includes a security management mechanism.
The many features of the Java language make it occupy a large market share among many programming languages. The Java language's support for objects and powerful APIs make programming easier and faster, and greatly reduce the cost of program development. Java's "write once, execute anywhere" is a major advantage that it attracts many businesses and programmers.