Knowledge Point Summary: 1 Java history  2 JDK configuration 3 file compilation and execution nbsp  4 escape character use &N Bsp  5 code practice content : Switch paths in the command window; write Hello Wor D Program detailed notes 1 The history of the computer. Hardware Memory, CPU hard drives are more important to developers. So the program runs through the CPU, the faster the speed, processing power and the stronger. 7200 rpm, 5400 rpm, etc.   2 The hard drive in the market is smaller than the actual memory size, because the manufacturer is based on 1000 of the binary units, not the 1024来. 3 java history Java's father JAmes Gosling 1995 A cross-platform object-oriented computer language 。   virtual machine jdk jre  JVM The software is required only by the JRE on the client, and the developer needs the JDK jre to contain the JVM. The JDK contains the JRE. 4 JDK environment variable configuration Find "Advanced system settings" in the computer properties to find the environment variable PATH, keep the original data, and at the end plus
Semicolon Pathpath for the path to install the JDK, find the JDK bin file path, note that the final is to end in Bin 5 test whether the installation is successful in the computer Start menu found running input cmd enter the command window, Output Java press ENTER, continue, lose Javac press ENTER. If no problem is configured to 6 CD/is back to the front of the root directory to continue to enter Dir is to let the command Window output folder in this directory, the conversion to the first root directory, and then enter D: or e: Carriage enter the corresponding directory Then enter the file name in the CD directory to change to the folder. 7 Create a folder in the E-drive, name it with the name of the hump, and build a Java document, write the program Hello Note: The 1 class name must be English and cannot be underlined and $. Write the program to save in time. The class name should be the same as the file name in the program. 8 put the written program in the command Window execution steps: First switch to the path of the folder after entering Javac Hello.java after the input Java Hello return to output results
9 Public class hello{ . public static void Main (string[] args) { &NBSP ; SYSTEM.OUT.PRINTLN (""); & nbsp } &N BSP;} 10 escape character \n wrap // Single line comment /* Multiline comment */ & nbsp \ t tab \ \ Escape \r Enter problems and Solutions: 1 System Write Error Error: The package system does not exist. Generally this is the sentence Syetem.out.println (""); Error form should be uppercase but lowercase, system written system.   Summary: Java Language is a case-sensitive computer language 2 When converting roots in cmd easily forget CD and then lose files Folder name, CD/is back to the beginning of the root directory. Note that you want to add a space after CD . 3 Java Chinese line one statement, System.out.println (""); If you press ENTER to write the contents of the brackets inside the parentheses, the error is as follows: Required ";" unfinished string literals illegal characters & nbsp Summary: newline symbols \ n similar escape characters and \ t tab stops &NBSP ; \ \ escape \r enter // Comments 4 Modify the name of the folder on the hard disk, the corresponding generated Java compilation file to change the name, the class name is also modified 5 summary
Java environment Configuration and Java history
