java base (1) ---- Introduction

1. Basic grammar,
2. Object-oriented,
3. Strings and collections,
4. I 流,
5. interface,
6. lambda、
7. Method references,
8. Stream、
9. Modular.

A, java Past and Present:

 

 J2SE: Standard trial version, J2EE: Enterprise Edition, J2ME: small version (mobile embedded development)

Second, the difference between JDK, JRE and the JVM

• JDK: java development kit, developed by the

(Includes JRE and development tools for developers to use)

• JRE: java runtime environment, use the run

　　(JVM and run library comprising, for operator use)

jvm is java virtual machine, is the real implementation of the program, JRE is the runtime environment, including libraries

• JVM: Java Virtual Machine, the core

　　Code (core containing byte code), in Java, the JVM will be appreciated that the bytecode is called (i.e. the .class file name extension), which does not face to any particular processor, only for the virtual machine.

Understanding xxx.class only this type of file, it is possible to class bytecode instructions file to identify and invoke the operating system API-up operation is completed. So, jvm is capable of cross-platform Java core

 Third, compile and run