Java BASICS (1) Java introduction to JDK installation and configuration environment variables constant variables data type Learning Forum, javajdk

Java BASICS (1) Java introduction to JDK installation and configuration environment variables constant variables data type Learning Forum, javajdk

The first day of Java introduces JDK installation and configuration environment variable constant variable data type Learning Forum

Java introduction:

Founder: James Gauss Lin, a giant. We stood on his shoulder and saw more.

Java is an object-oriented language that can be used across platforms. However, it is important to note that cross-platform Java is used, while JVM (Virtual Machine) is not cross-platform. Different systems have different JVMs, its existence implements cross-platform Java language. The code we write is. Java suffix file, compiled. Class file, which can be run on virtual levels of different systems. Currently, JDK is available in version 1.8 and is commonly used in version 1.7. Java is a great language. Although sun was acquired by Oracle, even if one day Java fell, its internal spirit will still be inherited.

Three frameworks of Java: JavaSE JavaEE JavaMe. I learned JavaEE and Enterprise Edition development. JavaSE is the most basic Java and implements core class libraries. Most of the applications are mini-game development earlier. JavaME, also known as embedded.

JDK installation and configuration of environment variables, configuration of environment variables, is to make every file of Java code can run.

Each basic learning volume of Java includes the history of Java, the most basic configuration, and so on. This is probably true for every language. I think it should be something I understand.

　　　　　　　　　　　　　　　

Constants and variables: constants are the amount that remains unchanged during the running of the program. variables are the amount that changes during the running of the program, essentially a space in the memory.

Data types include basic data types and reference data types:
There are eight basic data types:
Integer: byte short int long
Float Type: float double
Boolean: boolean (value: true, false)
Character Type: char

The basic data type can be divided into two categories: numeric type and boolean type. char is also a numerical type.

There are many types of reference interfaces, array string enumeration, enum

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