Introduction and characteristics of java

1.What is java?

Java is an advanced object-oriented programming language.

2. JVM

Java Virtual Machine is the key to cross-platform java programs. Different platforms have different JVMs, and the java word The section code does not contain any platform-related information and does not interact with the platform directly, but indirectly through the JVM. When the application is executed, the JVM loads the bytecode, interprets the bytecode into machine code for a specific platform, and lets the platform execute it.

Any application must be converted into machine code before it can interact with the computer. If the source of the machine code depends on the specific platform, then the application cannot be cross-platform. The machine code when the Java application is run is provided by the JVM, which is part of the Java system, and is not restricted by the platform, so it is cross-platform.

3.Java program running process

The source code written by the programmer is compiled by the compiler and converted into bytecode, and the bytecode is loaded to the JVM, which is interpreted by the JVM into machine code and run on the computer.

4.java version

For different purposes, java is divided into There are 3 versions:

1. Java SE: The standard version of java, which is the basis for other versions and is mainly used for developing desktop applications.

2. Java ME: The enterprise version of java, mainly used to develop enterprise-level distributed network programs.

3. # Java EE: Mainly used for embedded system development.

5.JDK

Java Develop Kits, a necessary tool kit for developing applications using the java language, mainly Includes compiler, JVM, Java basic API, etc.

6.JRE

Java Run Environment, the environment that java depends on, including JVM and java basic API.

7.API

Application Programming Interface, application programming interface, is the entrance to writing applications using java language, including source code, words Section code

Help document has three parts. An application consists of a series of methods. What are the requirements for methods? What methods are accepted by programming languages? The API provides some basic methods. To implement a certain function, programmers must follow the Java language specifications and call these methods to write more advanced methods.

8.java Features

1. Simple: The Java language was developed from C++, eliminating the complexity in C++ Parts that are difficult to grasp, such as pointers.

2. #Object-oriented: the basis of the java language. Java regards all problems as interactions between objects, and abstracts objects into collections of methods and properties.

3. #Distribution: includes two aspects: operation distribution and data distribution. Operation distribution refers to the completion of a function by multiple hosts, and data distribution means that the data distributed on multiple hosts is processed as a complete whole.
   Cross-platform: Applications written in Java are not subject to platform restrictions and can be migrated from one platform to another.

4. Interpreted type: The source code written in the Java language is converted into bytecode. The bytecode can only be executed by the computer when it is interpreted by the JVM into machine code.

5. #Safety: The underlying design of the Java language can effectively avoid illegal operations.

6. Robustness: Java provides many mechanisms to prevent serious errors at runtime, such as compile-time type checking and exception handling.

7. Multi-threading: Java supports multi-threading, allowing multiple threads within the process to work at the same time.

The above is the detailed content of Introduction and characteristics of java. For more information, please follow other related articles on the PHP Chinese website!