JAVA homework 1 (20200920)

Talk about the methods, experiences and lessons of learning programming languages ​​in the past. I
have learned C, C++ and Python. But the only programming language that has been studied carefully for a long time and has a certain understanding is C++.
About the
method of learning C++ : listen carefully to the class, understand carefully, and master the characteristics of the language in the application. In the process of after-class practice, you cannot blindly copy the contents of the books and the teacher's class. You must rely on your own memory and understanding to write the code to achieve a true understanding.
Experience: When encountering difficult problems, you can search for other people’s excellent code on the Internet, but you cannot copy and paste. You need to understand other people’s code. It is best to be able to simply state your ideas and pay attention after closing other people’s code. Point.
Lesson: Don’t use some simple but verbose code because of laziness, it will not benefit your own improvement at all.
What are the characteristics of the Java language?
Simple, object-oriented, platform-independent and portability, stability and security, multi-threaded and dynamic, high-performance, distributed.
What is the principle of Java cross-platform implementation?
Java is both a compiled and interpreted language. The compiled bytecode files are interpreted and executed by the Java virtual machine on different operating systems; Java data types are consistent on any machine, and it does not support specific hardware environments The same data type occupies the same amount of space in all operating systems.
(For example, the C++ used in the past is like going to fruit farmers to buy things, only local fruit growers can buy things, but Java is like an online shopping platform, so you can buy things from all over the world)
JDK, JRE, JVM have What are the differences?
JDK: Java development Kit, Java development kit
JRE: Java Runtime Environment, Java runtime environment
JVM: Java Virtual Machine, Java virtual machine