20165318 2017-2018-2 "Java programming" the first week of study summary

20165318 2017-2018-2 "Java program design" the first week of learning summarize the contents of learning Summary

The first chapter is a brief introduction to the Java platform, and explains how to build a Java environment.

Introduction to the Java platform

Through textbooks, quizzes, and queries, I learned about Java in the following sections:

• Java history
  In 1990, Sun established a development team led by James Gosling and was working on the development of a portable, cross-platform language capable of generating code that correctly runs on various operating systems and on a variety of CPU chips. The May 1995 release of the Java development Kit 1.0A2, unveiled by Sun, marks the birth of Java. The advent of Java marks the real advent of distributed systems.
• Three major platforms for Java
  Java SE (Java 2 Platform Standard Edition edition)
  Java EE (Java 2 Platform Enterprise Edition Corporate Edition)
  Java ME (Java 2 Platform Micro Edition mini version)

• Four components of Java SE
  Jvm:java virtual machines, included in the JRE
  Jre:java execution environment, required to run Java programs (including Java SE API,JVM, deployment technology)
  JDK: Includes jrk and tools needed in the development process, such as Javac, Java and other tool programs, the development of Java programs required
  If you just want to run a Java program, just have the JRE program.
  As long as the platform provides a Java runtime environment, Java-written software can run on it.

  DOS command

  Since I'm using bash in Windows, many commands in Linux are not available, so I searched for DOS commands online for use.
  Dir: Lists the files and folders in the current directory
  MD: Creating a Directory
  RD: Deleting a directory
  CD: Enter the specified directory
  Del: Delete Files
  Copy: Copying files
  xcopy: Copy Directory
  Tree: List directory tree
  ren: file name change
  Type: Display file contents
  CLS: Clear Screen
  Exit: Exit DOS command line

  Problems encountered in learning process and solutions

  Since I did not have a problem in the presence of problems, so only the problem and the solution, and did not
  Q: After installing the JDK, it is normal to enter Java at the command line, but the input javac is an error and will prompt for no such command.
  A: The current DOS command line window can be used temporarily after using path e:\jdk1.9\bin;%path%.
  Q:javac can be used, you cannot edit it using Java, even after setting the CLASSPATH environment variable.
  A: Since I did not initially install the directory to select the book, so some environment variables may be set error, so I reinstall the JDK, but there is no JRE file in JDK1.9, I found that can. %java_home%\lib\dt.jar;%java_home%\lib\tools.jar; To set up the classpath, the problem is resolved and the Java program runs successfully.
  In the use of the code cloud there are also some small problems, quickly resolved, so it is not stated.

20165318 2017-2018-2 "Java programming" the first week of study summary